KR20230174561A - Hybrid starter for Direct-On-Line starting with current ratio increase/decrease control function - Google Patents

Abstract

An embodiment of the present invention discloses a hybrid starter for direct-on-line starting that can limit rapid increases and decreases in current of a triac and protect hybrid relay contacts from short-circuit accidents during direct-on-line starting of an AC load.
The disclosed hybrid starter consists of a first relay and a triac connected in parallel with each other, a hybrid relay to connect or cut off AC power to the load according to a control signal, a current transformer to protect the load by detecting the variable ratio of the load current, and a hybrid A second relay connected in series with the relay to cut off the AC power from the load when the hybrid relay fails and the initial value is set, and thereafter to connect or cut off the AC power to the load according to the control signal, and a second relay to turn the load power on or off. A signal input means, a signal output means for outputting a trip or ready state, a signal input from the signal input means, a load current detected from the current transformer, and a voltage at both ends of the hybrid relay are detected and, if normal at startup, the It includes a microcontrol unit that controls the hybrid relay and the second relay to display a ready state on the signal output means and output a trip signal to the signal output means when a short circuit is detected.

Description

Hybrid starter for Direct-On-Line starting with current ratio increase/decrease control function}

The present invention relates to hybrid relay protection applied to the opening and closing contacts of a hybrid starter, and more specifically, to detecting the input voltage phase and load current during direct starting of an AC load, to detect a sudden increase or decrease in the critical rate of current of the triac. This is about a hybrid starter for direct on-line start to limit rise and decrease, dI/dt and (dI/dt)c) and protect hybrid relay contacts from short circuit accidents.

In general, AC motors have problems such as large starting currents that can cause thermal damage to the motor and the capacity of the circuit breaker that must be used increases, so various reduced voltage starting methods are used to lower the voltage at starting. These starting methods include reactor starting, Y-△ starting, and soft starter. Direct-on starting (full-voltage starting) is a method of starting directly at the rated voltage of the motor. The starting current generated at this time is 5 to 8 times the rated current and the starting torque is 100 to 200% of the rated torque, so the starting time is Although it is short, there is a lot of potential for mechanical damage due to voltage drop or increased torque, so it is mainly used for motors under 10 horsepower.

Relays for power control of direct-start AC devices include mechanical relays, solid state relays (SSRs), magnetic contactors, and hybrid relays. Unlike mechanical relays, semiconductor relays do not contain moving contacts, but are called non-contact relays as electronic switches that include a separate heat dissipation circuit due to internal heat generation proportional to the current. Like mechanical relays, electromagnetic contactors operate contacts by electromagnets, but their contact durability is high, so they are mainly used for industrial motor loads, and produce more noise and vibration than mechanical relays.

Hybrid relays combine mechanical relays and semiconductor relays in parallel, but unlike soft starters, they are used for direct-line starting or rated voltage starting, so they can be controlled by connecting only two phases even when connected to three-phase power. A more notable feature related to the control method is the principle that the semiconductor relay turns on/off only for a very short period of time (several ms) while the mechanical contact point is moving, so the spark (arc) of the mechanical contact point connected in parallel is reduced without internal heat generation of the semiconductor contact point, Noise and vibration are limited, and contact life can be extended several times that of an electromagnetic contactor. Therefore, hybrid relay is a technology that includes only the advantages of mechanical relay and semiconductor relay technology because it is easy to control load current without electrical noise (EMI) and does not generate heat, so it does not require a separate heat sink.

Meanwhile, the hybrid starter uses the hybrid relay circuit above, but adds a separate current detection circuit such as a CT current transformer to protect the load from various current faults, including overcurrent. In particular, the usage environment of hybrid motor starters used in industrial motors can be divided depending on the type of short-circuit protection. More specifically, internal relay contact burnout occurs after the circuit breaker (MCB) operates due to a short-circuit accident or during overcurrent protection of the motor starter. (IEC60947-4), Type 1 does not require reuse, but Type 2 requires it.

KR 10-1369032 B1 KR 10-1029924 B1

Although the conventional hybrid relay has the advantage of reducing electrical noise (EMI) or mechanical contact spark (arc), it is applied to industrial AC motors that require starting current tolerance of 6-7 times the rated current due to limitations in the control method. This is a difficult situation. In other words, the triac current fluctuation ratio (dI/dt) can rapidly increase due to the high starting current when the contact point of the hybrid relay is switched or turned on/off, and within a short period due to frequent starting/stopping or relay bouncing, etc. If contact switching occurs repeatedly, the electrical characteristics of the triac may deteriorate and the arc control function may deteriorate. In particular, a fault current is applied to the triac due to a delay in the operation of the external circuit breaker (MCB) or fuse during short-circuit operation, and the current fluctuation ratio exceeds the threshold required by the specification or the maximum allowable current (approximately 10 times the rated current). If it is exceeded, permanent damage to the triac will occur, and reuse upon trip recovery will not be possible, making it impossible to satisfy the short-circuit protection type type 2 requirements of the motor starter.

Additionally, other reasons why it is difficult to apply hybrid relays to AC motors are as follows. The combination of optical triac (Opto-traic) and RC snubber circuit, which is mainly used to reduce the rapid current fluctuation ratio of the triac, prevents malfunction due to the rapid voltage fluctuation ratio (dV/dt)c of the triac ( False turn-on) This is to protect the triac, but when the instantaneous contact point of a mechanical relay connected in parallel, such as a hybrid relay, is switched, electrical noise (EMI) and sparks (Arc) on both ends of the mechanical relay contact point are reduced by the operation delay time of the optical triac or Since it cannot be completely blocked during the gate current delay time, it becomes difficult to achieve the arc-free switching function that is intended for use.

The present invention is proposed to solve these conventional problems, and the technical problem to be solved by the present invention is to predict in advance the fault current due to a short circuit through detection of the input voltage phase when the hybrid relay is turned on, and to use the triac to reduce the rapid current ratio. Afterwards, the relay contact switching applies a stable DC triac gate current without delay at the zero point current, limiting the rapid increase/decrease of the triac current ratio (dI/dt & (dI/dt)c) to prevent electrical noise. The purpose is to provide a motor starter for direct on-line starting that implements arc-free switching without any (EMI) and further satisfies the motor starter's short-circuit protection type type 2.

An embodiment of the present invention limits the rapid current increase and decrease (Critical rate of current rise and decrease, dI/dt and (dI/dt)c) of the triac when starting an AC load directly and protects the hybrid relay contact from short circuit accidents. A hybrid starter for direct-on starting that can be started is disclosed.

The disclosed hybrid starter consists of a first relay and a triac connected in parallel with each other, a hybrid relay to connect or disconnect AC power to the load according to a control signal, a current transformer to protect the load by detecting the variable ratio of the load current, and a control signal. A second relay for blocking the AC power from the load when the hybrid relay fails or the initial value is set according to the signal, a signal input means for turning on or off the load power, and a signal output means for outputting a trip or ready state, The signal input from the signal input means, the load current detected from the current transformer, and the voltage at both ends of the hybrid relay are detected, and if normal during startup, a ready state is displayed on the signal output means, and if a short circuit is detected, the signal output means is displayed. Outputs a trip signal, applies a reduced short-circuit current at a low point of the preset input voltage waveform when the hybrid relay is turned on, predicts a fault current due to a short-circuit accident in advance, and protects the triac from a sudden increase in current ratio, If there is no problem, a stable DC triac gate current is applied to the gate of the triac without delay time at the zero point current to prevent a rapid increase or decrease in the current ratio (dI/dt & (dI/dt)c) of the triac when the relay contact is switched. It includes a microcontrol unit that controls the hybrid relay and the second relay to limit.

The microcontrol unit stores the half cycle (T) of the AC power in the initial value setting stage when power is applied, turns on the first transistor (TR1) through the first relay on (RL1 ON) command, and actually turns on the first relay. The time until the contact point (RL1-s) is turned on is counted and set as 'operating time (To)', the first relay off (RL1 OFF) command is issued, and the contact point (RL1-s) of the first relay is actually turned on. The time until it turns off is counted and set as 'release time (Tr)'.

The microcontrol unit optimizes zero current synchronization at the next start and stop by correcting the first coil voltage delay time (Td1 = T-To) or the second coil voltage delay time (Td2 = T-Tr) when switching contact points.

When starting and stopping, the microcontrol unit applies the triac gate current application period T/6 time points before the half cycle (T) of the zero point current, and delays it by T/6 time points beyond the half cycle (T), fixing it to a total of 2T/6 time points. The efficiency of the DC power circuit has been optimized.

In addition, the hybrid starter of another disclosed embodiment includes a first hybrid starter connected to any one of the three phases S, T, and R, and a second hybrid starter connected to any other phase to which the first hybrid starter is not connected among the three phases S, T, and R. A hybrid starter and a signal output means of the first hybrid starter are connected to a signal input means of the second hybrid starter, and a signal output means of the second hybrid starter is connected to a signal input means of the first hybrid starter. When one hybrid starter trips, a trip signal is transmitted to the other hybrid starter so that the first hybrid starter and the second hybrid starter trip together.

According to an embodiment of the present invention, the rapid current increase and decrease (Critical rate of current rise and decrease, dI/dt and (dI/dt)c) of the triac is detected through detection of the input voltage and load current phase during direct starting of the AC load. It has the effect of limiting and protecting the hybrid relay contacts from short circuit accidents.

In addition, according to an embodiment of the present invention, when the hybrid relay is turned on, the fault current due to a short circuit is predicted in advance through detection of the input voltage phase to protect the triac from a sudden increase in current ratio, and then the relay contact point is switched to a stable DC triac. By applying the gate current without delay at zero current, the sudden increase/decrease of the triac's current ratio (dI/dt & (dI/dt)c) is limited to achieve completely arc-free switching, and furthermore, the motor starter's short circuit protection type type 2. It has the advantage of satisfying .

1 is a schematic diagram showing a hybrid starter for direct-on starting according to an embodiment of the present invention;
Figure 2 is a flowchart showing the operation procedure of a hybrid starter for direct-on starting according to an embodiment of the present invention;
Figure 3 is an operation timing diagram of an example of applying a hybrid starter for direct on-line start to a single-phase motor according to an embodiment of the present invention;
Figure 4 is an example of applying the hybrid starter for direct-on starting according to an embodiment of the present invention to a three-phase motor;
Figure 5 is a timing diagram during normal operation when the hybrid starter for direct-on-line starting according to an embodiment of the present invention is applied to a three-phase motor;
Figure 6 is a timing diagram at the time of short-circuit start when the hybrid starter for direct-on-line start according to an embodiment of the present invention is applied to a three-phase motor.

The technical problems achieved by the present invention and its implementation will become clearer through preferred embodiments of the present invention described below. The following examples are merely illustrative for illustrating the present invention and are not intended to limit the scope of the present invention.

1 is a schematic diagram showing a hybrid starter for direct-on starting according to an embodiment of the present invention.

As shown in FIG. 1, the hybrid starter 100 for direct-on-line starting according to an embodiment of the present invention includes a micro control unit (MCU; 120) with a built-in DC power supply unit 110, ADC1 (122), and ADC2 (124). , first relay (RL1), triac (Q1), second relay (RL2), current transformer (CT), first transistor (TR1), second transistor (TR2), first optical device 130, It consists of 2 optical devices 140 and connects single-phase AC power input to the L1 line and L2 line to the single-phase load 10. Here, the first relay (RL1) and the triac (Q1) constitute the hybrid relay 150, ADC1 (122) is an analog-to-digital module for detecting the voltage across both ends of the hybrid relay, and ADC2 (124) is the load current. This is an Analog-to-Digital module for detection.

Referring to Figure 1, the DC power supply unit 110 is connected to the L2 line and the neutral (N) line to receive alternating current (AC) power and output 24V DC and 5VDC, and the single-phase load 10 has one end connected to the L1 line and It is connected and the other end is connected to the L2 line through the second relay contact point (RL2-s) and the first relay contact point (RL1-s), and the current transformer (CT) detects the load current flowing in the L2 line and ADC2 (124) It is designed to be passed on.

The hybrid relay 150 consists of a first relay (RL1) and a triac (Q1) connected in parallel with each other. The first relay (RL1) is a mechanical relay including a relay coil (RL1-coil) and a relay contact (RL1-s). When the first transistor (TR1) is turned on, the first relay coil (RL1- coil) is excited and the relay contact point (RL1-s) is connected, and when the first transistor (TR1) is turned off, the relay coil (RL1-coil) is deactivated and the relay contact point (RL1-s) is blocked. The main terminals (M1, M2) of the triac (Q1) are connected in parallel to both ends of the first relay contact (RL1-s), and the gate (G) of the triac is connected to the output terminal (O3) of the MCU (120). is connected to The contact state (voltage) of this hybrid relay 130 is transmitted to ADC1 (122) through resistors (R1 and R2) so that the MCU (120) can recognize it.

The second relay (RL2) is a mechanical relay including a relay coil (RL2-coil) and a relay contact (RL2-s). When the second transistor (TR2) is turned on, the second relay coil (RL2- coil) is excited and the relay contact point (RL2-s) is connected, and when the second transistor (TR2) is turned off, the relay coil (RL2-coil) is deactivated and the relay contact point (RL2-s) is blocked.

The first optical device 130 (Optical device 1) is an optical device for an external Start/Stop input signal. It receives the ON/OFF signal as an optical signal from the start switch (not shown) of the control panel and transmits it to the input terminal of the MCU 120. I1), and the second optical device 140 (Optical device 2) is an optical device for an external Ready output signal and is connected to the output terminal (O4) of the MCU 120 to output a Ready optical signal to the control panel. do. When the hybrid starter 100 according to an embodiment of the present invention is used for a three-phase load, the optical output of the second optical device 140 is in series with the optical input circuit of the first optical device 130 of another second hybrid starter. It is connected to and can stop operation together when the first hybrid starter trips.

The first transistor TR1 is for driving the first relay RL1 under the control of the MCU 120, and the second transistor TR2 is for driving the second relay RL2 under the control of the MCU 120. It is for this purpose.

As described in detail below, the microcontrol unit (MCU) 120 predicts the fault current due to a short circuit through detection of the input voltage phase when the hybrid relay is turned on, and protects the triac (Q1) from a sudden increase in current ratio. By applying a stable DC triac gate current to the triac gate (G) without delay time at zero point current, the rapid increase/decrease of the triac current ratio (dI/dt & (dI/dt)c) when switching relay contacts is limited to completely prevent the arc. It implements seamless switching and thus satisfies the short circuit protection type 2 of the motor starter.

Figure 2 is a flowchart showing the operation procedure of a hybrid starter for direct-on starting according to an embodiment of the present invention. Figure 2a is a flowchart showing the operation procedure for calculating parameters and starting when power is applied, and Figure 2b is an operation when stopped. This is a flowchart showing the procedure.

First, in an embodiment of the present invention, after the MCU 120 outputs a signal (RL1 ON command) for turning on the first transistor TR1, the actual first relay contact point RL1-s is connected and the load power is turned on. The time until operation is defined as 'operating time (To; operating time)', and after the MCU 120 outputs a signal (RL1 OFF command) to turn off the first transistor TR1, the actual first relay contact ( The time until RL1-s) is blocked and the load power is turned off is defined as 'release time (Tr; release time)'.

Referring to FIG. 2A, when AC power is input and power is supplied to the control circuit by the DC power supply unit 110, the MCU 120 monitors the hybrid relay state voltage of line L1 through ADC1 122 (S101, S102). As a result of monitoring, if the voltage is not detected for a certain period of time (e.g., 1 cycle of input frequency), the first relay (RL1), the second relay (RL2), and the triac (Q1) are in the off state (0V), so the operating time (To) and release time (Tr).

In the operating time (To) parameter calculation step (S103), the MCU (120) turns on the first transistor (TR1) through the first relay on (RL1 ON) command, and then turns on the actual contact point (RL1-s) of the first relay. The time until the voltage of ADC1 (122) is turned on and the voltage of ADC1 (122) becomes Vcc is counted and stored in the built-in memory as a parameter called 'operating time (To)'.

Then, in the release time (Tr) parameter calculation step (S104), the MCU (120) issues a first relay off (RL1 OFF) command, and the contact point (RL1-s) of the first relay is actually turned off, so that the voltage of ADC1 (122) is turned off. The time until it reaches 0V is counted and stored in the internal memory as a parameter called ‘release time (Tr)’.

And if the contact states of the first and second relays (RL1, RL2) and the triac (Q1) are all normal, the MCU (120) turns on the second optical device (Optical device 2; 140) for the ready output signal. (On) and switches to start-up preparation state (S105).

When the start switch is turned on in the start ready state and the input signal (On) of the first optical device (Optical device 1; 130) is confirmed, the MCU 120 turns on the second transistor (TR2) to transmit the second relay (RL2). ), check that the input voltage waveform decreases through ADC1 (122), and wait until the hybrid relay's short circuit protective voltage (e.g., 7~12V) is confirmed (S108). Here, the short-circuit protection voltage can be set in advance so as not to exceed the threshold (dI/dt) for rapid current ratio increase of the triac during protection operation by considering the circuit impedance in the short-circuit state. However, if it is difficult to check the circuit impedance, the triac gate Set the current application time so that it ends as close to but earlier as possible than the zero point voltage of the input voltage waveform.

When the short circuit protection voltage is confirmed through ADC1 (122), the MCU (120) applies the triac gate current (Gc1) only for a very short period (e.g., 100 ㎲) to check for short circuit, and ADC2 (124) Check the instantaneous current rise and calculate the maximum current in the circuit impedance or steady waveform (Full since wave) (S109). At this time, the triac gate current (Gc1) is blocked before the phase inversion of the load current. This means that when the fault current is less than a few V of the input voltage sine waveform, the triac gate current (Gc1) is delayed by the circuit inductance (L) until the phase inversion occurs. Using the characteristic (Time constant (τ) = Inductance (uH) / Resistance (m-ohm)), the load current (I) is calculated as follows in Equation 1.

For example, short circuit protection voltage (V) = 12V, 400V transformer resistance (R) = 5m-ohm, inductance (L) = 0.1mH, triac gate current application time = 100uS, current ratio increase threshold dI/dt = 50A/us. In this case, the actual sensing current I is 12A, which is lower than the threshold of 50A, as shown in Equation 2 below,

If the calculated maximum current (V/R) exceeds the preset protection current value, it trips immediately and the hybrid starter 100 maintains the OFF state (S115, S116). When using the hybrid starter 100 according to an embodiment of the present invention in a three-phase electric motor, two hybrid starters 100-1, 100-2 are used as will be described in detail later, so a second optical device (Optical device 2; 140) is used. ) stops the Ready signal output, and as the LED turns off, a stop signal is sent to the first optical device (Optical device 1 (Start/Stop) 130) of another hybrid starter connected to the phase whose phase angle is delayed by 120 degrees. input so that both the first and second hybrid starters (100-1,100-2) maintain the trip state.

Meanwhile, if the calculated maximum current (12A) is less than the preset allowable current (50A) as in the above embodiment, the triac gate current (Tc2) is reapplied for a short period at the zero point voltage to turn on the triac (Q1). , After the first coil voltage delay time (Td1 = T-To, where 'T is half cycle'), the first transistor (TR1) is turned on with the RL1 ON command to excite the first relay coil (RL1-coil) (S111, S112). If the half cycle (T) of the input voltage is smaller than the operating time (To), the RL1 coil (RL1-coil) is excited first by the difference. In an embodiment of the present invention, for convenience of understanding, it is assumed that the half-cycle (T) is greater than or equal to the operating time (To). Afterwards, according to the stored operating time (To), after a half cycle, the load current is switched from the triac (Q1) to the first relay contact (RL1-s) at the approximate zero point current, and normal operation begins. Since the transition is made at the approximate zero point current in this way, the triac current does not exceed the rapid current ratio decrease threshold (dI/dt)c.

At this time, the MCU (120) was detecting the phase reversal of the triac current, so in the next time, the first coil voltage delay time (Td1 = T-To) was set so that the hybrid contact point transition occurs at a point closer to the zero point current than before. Calibrate (S113).

And when the load current supply is switched to the first relay contact (RL1-s), the triac is turned off and normal operation begins (S114).

On the other hand, the triac DC gate current (Gc3) application time is related to the power consumption of the power supply unit 110 and needs to be minimized. When connecting a three-phase power supply, the current phase change (resistive load) due to sequential phase intervention of the hybrid relay In this case, to compensate for the maximum lead of 30 degrees (-T/6), the gate current begins to be applied from T/6 before the half cycle of the input voltage (T - T/6). Additionally, the minimum time for the gate current application period can be set in advance by considering mechanical relay contact bouncing. However, considering the current delay or unbalanced current of inductive loads such as motors, the initial value can be set to a total time of 2T/6 (e.g., 2.8ms if the power frequency is 60Hz) until (T+T/6). there is. However, when used in a field that requires frequent starting and stopping, or when the number of contact bouncing increases due to mechanical fatigue of the mechanical relay, rapid changes in the current ratio of the triac (Q1) accumulate over time and change the electrical characteristics. may lead to degradation. For example, if the point of contact transition from triac to mechanical is somewhat fast or slow in the zero current phase and the triac current reduction ratio (dI/dt)c exceeds the threshold, the characteristics of the triac voltage variation ratio (dV/dt)c Due to the drop, the triac can be forced to remain on until the load current is cut off even if there is no gate current (Falso trun on), and when it stops, the load current cutoff function of the hybrid relay is temporarily lost and the second relay (RL2) connected in series. An arc occurs at the contact point. Therefore, the MCU 120 detects the phase reversal of the triac current at every startup and corrects the coil voltage delay time (T-To) so that the hybrid contact point transition occurs at a point closer to the zero current than before.

Referring to Figure 2b, during normal operation, the load current is continuously detected through ADC2 (124), and then an Off signal (STOP command) is input through the first optical device (Optical device 1; 130) or a trip occurs. If so, the MCU 120 turns off the first transistor TR1 with the RL1 OFF command after the second coil voltage delay time (Td2 = T-Tr) according to the release time (Tr) previously stored at the zero point current, In order to cut off the relay coil power and bypass the load current from the subsequent zero point current from the first relay contact point to the triac (Q1) connected in parallel, (T + T) from the time before the zero point current T/6 (T - T/6) /6) Turn on the triac (Q1) by applying the gate current (Gc3) for a total of 2T/6 time (S201 to S203) and limit the rapid current ratio increase (dI/dt) of the triac current ( S204). If the triac current increase ratio (dI/dt) exceeds the critical value, the triac may be permanently damaged. Therefore, as at startup, the second coil voltage delay time (Td2 = T-Tr) is corrected, and when the triac (Q1) is turned off and the triac current is blocked, the second relay (RL2) is opened (S205 to S207) .

On the other hand, if a short circuit occurs during normal operation and the load current exceeds the triac maximum current threshold, the external circuit breaker (MCB) operates, waits until the load current stabilizes (e.g., up to 100 ms), and then trips (S211~) S214). Therefore, the external breaker operating current must be lower than the triac maximum current threshold.

Figure 3 is an operation timing diagram of an example of applying a hybrid starter for direct starting according to an embodiment of the present invention to a single-phase motor, where (A) is a waveform diagram showing the hybrid relay contact voltage (H.R. contact voltage (ADC1)), and (B) ) is a waveform diagram showing the phase current (ADC2), (C) is a waveform diagram showing the triac contact status (Q1), and (D) is a waveform diagram showing the triac gate current (Triac gate current). Current; G), (E) is a waveform diagram showing the state of the first relay contact (Relay contact Status; RL1), and (F) is a waveform diagram showing the voltage of the first relay coil (Relay coil Voltage; This is a waveform diagram showing RL1).

Referring to FIG. 3, when the power is turned on, the MCU (120) monitors a decrease in the voltage of the hybrid relay (HR) contact point through ADC1 (122) and then detects a short circuit protection voltage (Short ciruit protective voltage) as shown in (A) of FIG. When voltage) is confirmed, the triac gate current (Gc1) of a very short period (several tens of uS) is applied to detect a short circuit as shown in (D) of Figure 3, and the instantaneous current rise value is checked with ADC2 (124). Then, determine whether there is a short circuit by calculating the maximum current in the steady waveform (Full since wave). At this time, the triac gate current application time is cut off before phase inversion occurs.

If a short circuit is not detected, the MCU 120 reapplies the triac gate current (Gc2) at the zero point voltage for a short period as shown in (D) of FIG. 3, and the coil voltage delay time (Td1 = T-To, where T (half cycle), drives the first transistor (TR1) to excite the first relay coil (RL1-coil), and accordingly, the first relay contact (RL1-s) reaches zero after the To time as shown in (E) of FIG. 3. Turn it on at the current position. At this time, the current is applied to the triac gate (G) at T/6 before the zero point current and continues until T/6 after the zero point current to improve the efficiency of the power supply unit 110. In other words, the triac (Q1) DC gate current application time is correlated with the power consumption of the power supply and needs to be minimized. In the embodiment of the present invention, the current phase change due to sequential phase intervention according to the load type (e.g., the resistive load) In order to compensate for a maximum lead of 30 degrees (-T/6), the gate current begins to be applied from T/6 before the half cycle of the input voltage (T-T/6). And the minimum gate current application time is a total of 2T/6 (e.g., 2.8ms if the power frequency is 60Hz) until (T+T/6) considering relay bouncing time or current delay of inductive load such as motor. You can set the initial value with .

Thereafter, when an Off signal is input through the first optical device (Optical device 1; 130), the MCU (120) continuously detects the load current during operation through ADC2 (124) and then detects the load current through ADC2 (124) in FIG. 3 (F). As shown, after the second coil voltage delay time (Td2 = T-Tr) obtained by subtracting the release time (Tr) from the zero current, the first transistor (TR1) is turned off to block the first relay coil power, and the first relay coil power is blocked, as shown in (D) of FIG. 3. ), for a total of 2T/6 (e.g., 2.8ms if the power frequency is 60Hz) from the time T/6 before the half cycle of the input voltage (T-T/6) until the time the gate current is applied (T+T/6). Maintain the gate current.

Accordingly, even when the motor is stopped (STOP), the load current is bypassed from the first relay contact (RL1-s) to the triac (Q1) connected in parallel at the zero point current, resulting in arc generation and a sudden increase in the current ratio of the triac current (dI/ dt) can be limited.

Figure 4 is an example of applying the hybrid starter for direct-on starting according to an embodiment of the present invention to a three-phase motor, in which the first hybrid starter (100-1) is connected to the S phase and the second hybrid starter (100-1) is connected to the T phase. -2) is connected. In the embodiment of the present invention, the first and second hybrid starters (100-1,100-2) are described as connected to the S phase and the T phase, respectively, but the first and second hybrid starters (100-1,100-2) are connected to the R and S phases or the T and R phases. Even if you connect 100-1,100-2) in each order, there is no difference in operation characteristics.

Referring to Figure 4, the U winding of the three-phase electric motor 20 is connected to the R phase through a relay, the V winding is connected to the S phase through the first hybrid starter 100-1, and the W winding is connected to the second phase. It is connected to the T phase through the hybrid starter (100-2). Additionally, when the hybrid starter 100 is used in three phases, the output of optical device 2 (140) of the first hybrid starter (100-1) is the input of optical device 1 (130) of the second hybrid starter (100-2). is connected, and the output of optical device 2 (140) of the second hybrid starter (100-2) is connected to the input of optical device 1 (130) of the first hybrid starter (100-1), so that any one hybrid starter When tripped, other hybrid starters are also tripped so that both the first hybrid starter (100-1) and the second hybrid starter (100-2) are tripped.

That is, when the maximum current calculated from the first hybrid starter (100-1) exceeds the preset protection current, the first hybrid starter (100-1) trips and transitions to the OFF state, thereby causing the second optical device (Optical The Ready signal output of device 2; 140 is stopped, the LED is turned off and the phase angle is delayed by 120 degrees. The first optical device (Optical device 1; 130), a trip (Off) signal is input. Accordingly, the first and second hybrid starters 100-1 and 1100-2 all transition to the trip state.

In this way, the operations of the first hybrid starter (100-1) and the second hybrid starter (100-2) are similar to the single phase described above, except that when a trip occurs in any one hybrid starter, the other hybrid starter also trips. Since it is the same as the operation of the hybrid starter 100 of the embodiment, further description will be omitted.

Figure 5 is an operation timing diagram during normal operation of the example of applying the hybrid starter for direct-on-line starting according to an embodiment of the present invention to a three-phase motor. (A) shows the current waveforms of the S phase and T phase, and (B) shows the current waveforms of the S phase and T phase. It shows the state of the triac contact of the first hybrid starter, (C) shows the triac gate current waveform of the first hybrid starter, and (D) shows the state of the first relay contact of the first hybrid starter. It was done. Additionally, (E) shows the triac contact state of the second hybrid starter, (F) shows the triac gate current waveform of the second hybrid starter, and (G) shows the first relay of the second hybrid starter. It shows the state of the contact point.

Referring to FIG. 5, when the first hybrid starter (100-1) and the second hybrid starter (100-2) detect a short-circuit protection voltage, they apply a first gate current (Gc1) of a very short period to check whether a short-circuit exists. After checking, if a short circuit does not occur during startup, the second gate current (Gc2) of a very short period is applied immediately to enable switching at the zero point voltage, and the gate current (Gc2) is applied T/6 before the half cycle (T). After applying Gc3), it is applied until T/6 after the half cycle (T) so that the cycle of the gate current (Gc3) is 2T/6.

Figure 6 is an operation timing diagram during short-circuit start in the example of applying the hybrid starter for direct-on-line start to a three-phase motor according to an embodiment of the present invention. (A) shows S-R shorted, T-R shorted, and S-T shorted. (B) shows the current waveform at the time of tripping due to (S-T shorted), (B) shows the triac gate current waveform of the first hybrid starter when S-R shorted (S-R shorted), (C) shows the current waveform at the triac gate when S-R shorted (S-R shorted) ) shows the triac gate current waveform of the second hybrid starter. (D) shows the triac gate current waveform of the first hybrid starter when T-R shorted, and (E) shows the triac gate current waveform of the second hybrid starter when T-R shorted. will be. Additionally, (F) shows the triac gate current waveform of the first hybrid starter when S-T is shorted, and (G) shows the triac gate current waveform of the second hybrid starter when S-T is shorted. It was done.

Referring to FIG. 6, the first hybrid starter 100-1 is connected to the S phase, and the second hybrid starter 100-2 is connected to the T phase.

When S-R shorted (S-R shorted), the first hybrid starter (100-1) detects the S-R short circuit through the triac gate current (Gc1) as shown in (B) of FIG. 6, and accordingly, the first hybrid starter (100-1) As 1) is tripped, the second hybrid starter 100-2 is also tripped through the transfer of a trip signal between the second optical device 140 and the first optical device 130.

When T-R is shorted (T-R shorted), the first hybrid starter (100-1) fails to detect the short circuit through the triac gate current (Gc1) as shown in (D) of FIG. 6 and applies the triac gate current (Gc2). The second hybrid starter (100-2) detects a T-R short circuit through the triac gate current (Gc1) as shown in (E) of FIG. 6, and accordingly, the second hybrid starter (100-2) trips and the second The first hybrid starter 100-1 is also tripped by transmitting a trip signal between the optical device 140 and the first optical device 130.

When S-T is shorted (S-T shorted), the first hybrid starter (100-1) does not detect the short circuit through the triac gate current (Gc1) as shown in (F) of FIG. 6, and thus applies the triac gate current (Gc2). The second hybrid starter (100-2) detects the S-T short circuit through the triac gate current (Gc1) as shown in (G) of FIG. 6, and accordingly, the second hybrid starter (100-2) trips and the second The first hybrid starter 100-1 is also tripped by transmitting a trip signal between the optical device 140 and the first optical device 130.

In the above, the present invention has been described with reference to an embodiment shown in the drawings, but those skilled in the art will understand that various modifications and other equivalent embodiments are possible therefrom.

10: single-phase load 20: three-phase load
100,100-1,100-2: Hybrid starter 110: Power unit
120: Micro control unit (MCU) 122: ADC1
124: ADC2 130: first optical device
140: second optical device 150: hybrid relay

Claims (5)

A hybrid relay consisting of a first relay and a triac connected in parallel to each other to connect or block AC power to the load according to a control signal;
Current transformer (CT) to detect load current and protect the load;
Relay both ends voltage or short-circuit protection voltage detection circuit;
a second relay connected in series with the hybrid relay;
Signal input means for turning on or off load power;
Signal output means for outputting a trip or ready state; and
The signal input from the signal input means and the voltage at both ends of the hybrid relay are detected, and when the input voltage decreases during startup and the preset short circuit protection operating voltage is confirmed, the triac gate current is applied and the detected current is used to prevent short circuit accidents. If a fault current is predicted, a protective trip is performed by blocking the gate current before the phase inversion of the triac current. If a fault current is not predicted, the load current detected from the current transformer is continuously detected and the contact point of the hybrid relay is switched at the zero point current. A hybrid starter for direct-on-line starting that includes a microcontrol unit that induces and limits the sudden increase or decrease in current ratio (dI/dt, (dI/dt)c) of the triac. The method of claim 1, wherein the microcontrol unit
When applying power, specify the half cycle (T) of the AC power in advance in the initial value setting step,
When the second relay is off, the first transistor (TR1) is turned on through the first relay on (RL1 ON) command, and the time until the contact point (RL1-s) of the first relay is actually turned on is counted to ' Set to 'Operating Time (To)',
A hybrid for direct starting, characterized by issuing a first relay off (RL1 OFF) command, counting the time until the contact point (RL1-s) of the first relay is actually turned off, and setting it as 'release time (Tr)'. Starter. The method of claim 1, wherein the microcontrol unit
At startup, the contact transition from the triac to the relay is synchronized to the zero point current through the first coil voltage delay time (Td1 = T-To), thereby limiting the rapid decrease in the triac current ratio ((dI/dt)c) and stopping. At this time, the contact transition from the relay to the triac is synchronized to the zero point current through the second coil voltage delay time (Td2 = T-Tr) to limit the rapid increase in the triac current ratio (dI/dt), and the contact transition is When completed, the first and second coil voltage delay times (Td1, Td2) are respectively corrected in comparison with the load current phase to optimize zero current synchronization at the next start and stop. The method of claim 1, wherein the microcontrol unit
When starting and stopping, the triac DC gate current application time begins to be applied T/6 times before the zero point current at which the hybrid contact point is switched, and is delayed by T/6 points compared to the zero point current, fixed to a total of 2T/6 points, and the DC power circuit A hybrid starter for direct-on start, characterized by optimized efficiency. A first hybrid starter connected to any one of the three phases S, T, and R;
A second hybrid starter connected to the other phase of the three phases S, T, and R, which is delayed by 120 degrees from the phase to which the first hybrid starter is connected; and
Connecting the signal output means of the first hybrid starter to the signal input means of the second hybrid starter, and connecting the signal output means of the second hybrid starter to the signal input means of the first hybrid starter;
The first and second hybrid starters sequentially perform the short-circuit protection operation of claim 1, and when one hybrid starter trips, a trip signal is transmitted to the other hybrid starter to protect the first hybrid starter and the second hybrid starter. A hybrid starter for direct on-line starting that trips together.