JP4069328B2 - Refrigeration cycle equipment - Google Patents

Description

  The present invention relates to a refrigeration cycle apparatus (air conditioner, refrigeration apparatus, etc.) provided with a compressor driven by an electric motor provided with a permanent magnet in a rotor, and in particular, a cage shape that functions as an induction motor in an iron core of a rotor. This is suitable for a conductor and a permanent magnet that is magnetized so as to function as a synchronous motor.

  Refrigerant compressors used in refrigeration cycle devices that use a vapor compression refrigeration cycle include constant-speed compressors that are driven at a substantially constant rotational speed and inverter-type compressors that control the rotational speed. An induction motor provided with a squirrel-cage conductor (winding) is often employed because it can be easily driven by voltage. However, recently, an embedded magnet synchronous motor has been proposed as one capable of driving a commercial power source with high efficiency from the viewpoint of high efficiency.

  When starting the refrigeration cycle, if the pressure difference between the discharge side and the suction side of the compressor is large, it will be impossible to start, or if an overload occurs during steady operation, that is, during synchronized operation, If the compressor discharge pressure exceeds the set pressure value during the operation of the refrigeration cycle, the rotor of the motor may stall significantly and the reliability of the equipment may be significantly impaired. It is known to bypass the suction side and the suction side, and is described in Patent Document 1, for example.

  In addition, since the load on the compressor is not uniform, if an excessive load is generated, an excessive current flows in the winding of the motor, and the magnet used in the rotor is demagnetized by the magnetic field generated thereby. In order to prevent this, the current value of the compressor is detected, and when a set current is generated, the power supply is shut off. Further, it is known that the current value to be cut off is lower when the temperature is low than when it is high. For example, it is described in Patent Document 2.

JP 2001-227778 A JP-A-7-67390

  In the above prior art, the one described in Patent Document 1 is good in that starting is ensured by the differential pressure between the discharge side and the suction side of the compressor and stalling during steady operation is prevented. Asynchronous (step-out) is not directly detected, there is a risk that reliability may be reduced or demagnetization may occur due to step-out.

  Moreover, in the thing of patent document 2, when it becomes excessive by the magnitude | size of an electric current, since it only interrupts | blocks an electric current, depending on the time required for electric current interruption, a demagnetization phenomenon cannot be avoided, and reliability is improved. There was a need to improve. In addition, the current value alone cannot prevent the motor from being stalled, vibration due to cocking, etc., and the refrigeration cycle will not be affected. Overload will occur during steady operation of the refrigeration cycle, that is, synchronous operation. In the worst case, the rotor of the synchronous motor stalls greatly, the winding temperature of the motor rises, and the insulation material of the winding deteriorates or the insulation of the winding breaks down. It could be severely damaged.

  The object of the present invention is to solve the above-mentioned problems of the prior art, more accurately determine the magnitude of the load, eliminate instability in the refrigeration cycle due to step-out and demagnetization, and provide highly reliable embedded magnet synchronization The object is to provide a refrigeration cycle apparatus using an electric motor.

In order to achieve the above object, the present invention provides a refrigeration cycle apparatus having a refrigeration cycle in which a compressor, a condenser, a condenser blower, an evaporator, and an expansion valve are sequentially connected. outer peripheral cage winding is formed, an electric motor in which a permanent magnet is embedded which is magnetized in multipolar on the inside, and a driving current detecting means for detecting an operating current of the motor, the distortion of the driving current When the value of the distortion becomes a set value or less while the motor is operating as a synchronous motor , the power supply to the motor is cut off .
Here, the value of the distortion of the operating current can also be obtained based on the harmonic current component included in the operating current.

Moreover, in the above, it is desirable that the permanent magnet is magnetized in two poles.
Furthermore, in those described above, it is desirable to control the air volume of the condenser blower in accordance with the distortion value of the operating current.

Furthermore, in the above, it is desirable to control the opening degree of the expansion valve in accordance with the value of distortion of the operating current.
Furthermore, in the above, it is desirable to provide a temperature sensor for detecting the surface temperature of the compressor, and to reduce the set value when the surface temperature becomes high.

Furthermore, in the above, it is preferable that the permanent magnet is magnetized in two poles and the compressor is a scroll compressor.
Furthermore, in those described above, it is desirable to control the air volume of the condenser blower in relation to the temperature of the compressor and strain values of the operating current.

Furthermore, in those described above, it is desirable to control the opening degree of the expansion valve in relation to the temperature of the strain value and the compressor of the driving current.
Further, in the above, the permanent magnet is magnetized in two poles, the compressor is a scroll compressor, the electric motor is driven by an inverter device composed of a power transistor, It is preferably performed by shutting off the power transistor of the inverter device when the current distortion value is equal to or lower than a set value .

  Further, the present invention provides a refrigeration cycle apparatus having a refrigeration cycle in which a compressor, a condenser, a condenser blower, an evaporator, and an expansion valve are sequentially connected. An electric motor in which a permanent magnet magnetized with a plurality of poles is embedded, and an operating current detection means for detecting an operating current of the electric motor, and a distortion factor of the operating current and at least the Control is performed in association with either the air volume of the condenser blower or the opening of the expansion valve.

  According to the present invention, since the load is determined by the distortion component of the operating current of the motor, the magnitude of the load is more accurately determined for the compressor using the embedded magnet synchronous motor, and the step-out, demagnetization is performed. It is possible to eliminate the instability of the refrigeration cycle due to the high reliability.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 shows an apparatus using a refrigeration cycle, for example, an air conditioner. In order to improve the efficiency of air conditioners that use a vapor compression refrigeration cycle, it is effective to improve the efficiency of the motor used in the refrigerant compressor that consumes the largest amount of power among the components that make up the refrigeration cycle. As a high motor, a synchronous motor in which a permanent magnet is embedded in a rotor core is known. Since the synchronous motor rotates by using the magnetic field generated by the permanent magnet embedded in the rotor of the motor and the stator, the induction motor generates a secondary current that flows to the motor rotor. Therefore, the efficiency is increased because there is no energy loss. However, when a synchronous motor is used as an electric motor used for a refrigerant compressor, the rotor has a large inertial force because it is integrated with a rotating component of the refrigerant compressor. Therefore, at the time of starting, the rotor cannot follow the rotation speed of the rotating magnetic field generated from the stator, and the refrigeration cycle cannot be started.

  Therefore, in a refrigeration cycle using an embedded magnet synchronous motor, a squirrel-cage winding 110 that acts as an induction motor is incorporated when the rotor core of the motor used in the compressor is below the synchronous speed, and further inside the rotor core. A permanent magnet 100 magnetized in two poles is embedded.

  The air conditioner shown in FIG. 1 constitutes a refrigeration cycle in which a compressor 130, a condenser 140, a condenser blower 145, an evaporator 150, and an expansion valve 160 are sequentially connected. The electric motor used for the compressor 130 forms a squirrel-cage winding (conductor) 110 in the circumferential direction in the vicinity of the outer periphery of the rotor, and the permanent magnet 100 is embedded in the rotor, thereby rotating the rotor. It acts as an induction motor until the speed reaches the synchronous speed, and works as a synchronous motor when the rotational speed of the rotor reaches the synchronous speed. Therefore, it is possible to start without using an inverter, and at the time of operation at a synchronous speed, that is, at a rotational speed (3000 r / min, 3600 r / min) determined by the power frequency (50/60 Hz) of the commercial power source and the number of poles. During the steady operation, the secondary current is not generated in the rotor of the electric motor, so that the efficiency can be improved.

  In other words, since the synchronous motor does not cause slippage between the stator and the rotor that were in the induction motor, the load fluctuation in the rotational speed of the rotor is small compared to the induction motor. Since the rotational speed becomes faster, the amount of refrigerant compressed by the refrigerant compression mechanism of the compressor 130 also increases, the refrigerant discharge amount of the compressor 130 increases, and the capacity is improved in the normal load range of the refrigeration cycle. Can do.

  In particular, even during operation when the refrigeration cycle is overloaded, slip is zero in the synchronized state, and no current flows through the squirrel-cage winding 110. The effect of improving becomes very large. Furthermore, if the compressor 130 is a scroll compressor, the variation in the compression torque is small, and therefore the load variation on the motor is small, so that the efficiency can be further improved.

  An operating current detecting means 180 for detecting the operating current of the compressor 130, a temperature sensor 190 for detecting the surface temperature of the compressor 130, and a waveform distortion determining means 200 are mounted on the control device 171 of the air conditioner 170, and the electric motor is It is connected to a power source via an operating current detecting means 180 composed of a resistor or the like and a power switch 205.

  The permanent magnet 100 is magnetized by generating a magnetic field by causing a current larger than the current that flows when the compressor is operated to the cage winding 110 of the compressor 130. Further, once magnetized, if an excessive current flows through the squirrel-cage winding 110, a demagnetization decrease in which the magnetic force of the permanent magnet 100 is lost occurs. The current value at this time is a value at which the magnetizing current is also small, and when the temperature of the permanent magnet 100 is high, the current value leading to demagnetization becomes small. That is, the motor of the compressor 130 including the rotor 120 composed of the permanent magnet 100 and the squirrel-cage winding 110 is operated as a synchronous motor. There was a possibility that a demagnetization phenomenon of the magnet 100 occurred.

  The compressor 130 including the rotor 120 composed of the permanent magnet 100 and the squirrel-cage winding 110 starts up as an induction motor with a squirrel-cage winding at the time of startup and is driven as a synchronous motor with a rotor of a permanent magnet near the synchronous speed. However, the operating current waveform of the squirrel-cage winding 110 is a sine wave as an induction motor, and when operated as a synchronous motor, an armature reaction occurs due to the permanent magnet 100 and affects the field main magnetic flux. The wave is distorted.

  Therefore, when most of the operating current flowing through the main winding is used as the field current of the induction motor, the distortion of the operating current waveform is small, and when used as the field current of the synchronous motor, the distortion is large. Become. Further, the compressor 130 has a distortion in the operating current below the rated load, and as the load increases and the torque becomes insufficient, the current increases to supply the squirrel-cage winding excitation current, and the distortion decreases.

  The upper diagram of FIG. 3 shows the operating current waveform at the rated load (horizontal axis: time, vertical axis: current), and the lower diagram shows the frequency analysis diagram (horizontal axis: order, vertical axis: primary: 100) Ratio). Similarly, the upper diagram of FIG. 4 is an operating current waveform at an overload, and the lower diagram is a frequency analysis diagram thereof. As shown in the figure, when the operating current of the compressor is below the rated output, the 4th to 10th harmonic current components are larger than the primary components, the distortion is 10.7%, and the load is increased. The 10th harmonic current component is reduced, and the overall distortion is 7.7%.

  In addition, FIGS. 5 and 6 are obtained by changing the voltage under the same load condition. FIG. 5 shows an operating current waveform when the rated voltage is 200 V, FIG. 5 is 180 V, and FIG. (Figure below). The distortion is 6% at a rated voltage of 200V, but is 6.9% at 220V and 5% at 180V. This is because when the voltage is low, the output of the synchronous motor using the permanent magnet 100 becomes insufficient due to a decrease in the field current, and the current increases, and an exciting current is passed through the cage winding 110 to operate as an induction motor.

  Therefore, the current detected by the operating current detection means 180 is converted into digital data by an AD converter, and the distortion rate is set to a set value, for example, 6 to 11%, preferably 7% or less, by the waveform distortion determination means 200 that performs the calculation. Or when the content of the 10th harmonic is 4-7% or less, preferably 5% or less, the compressor power switch 205 is shut off. Then, step-out occurs due to insufficient torque, preventing overcurrent and demagnetizing the permanent magnet 100, and preventing the refrigeration cycle from becoming unsynchronized and becoming unstable.

  Although the distortion rate is calculated by the waveform distortion determination means 200, a value related to the distortion of the operating current may be obtained, and if this value becomes equal to or less than the set value, the energization to the motor may be cut off. Furthermore, as a method of detecting the distortion rate or distortion component and the value related to the distortion, a pulse signal corresponding to the presence or absence of a change in the operating current is generated. For example, when the current is AD converted, the converted value is AD converted Whenever the change is greater than a certain value, a high level signal is output, and otherwise a low level signal is output. The magnitude of the duty ratio of the pulse signal may be a distortion rate, a distortion component, or a value related to distortion. In addition, the pulse signal is counted, integrated to calculate the average value, and the output pulse signal is passed through an integration circuit consisting of a resistor and a capacitor to obtain a value related to the operating current distortion at that voltage level. This makes the calculation easier.

  In order to calculate each harmonic order, it is common to perform a Fourier analysis of the detected current waveform and expand it to the harmonic order. However, this requires a high-speed arithmetic element and a built-in refrigeration cycle. It is not suitable as a built-in element of the equipment.

  Therefore, in FIG. 3, the following method may be used as a method of measuring the distortion of the current. In other words, instead of detecting the distortion factor of the current waveform or the frequency component that constitutes it, attention is paid only to the necessary frequency component such as the 8th to 11th orders. Since the 8th to 11th order waveforms are likely to appear as distortion of the entire current waveform, the waveform is estimated from the waveform shape. For example, an ideal sine waveform is calculated from the frequency and peak current of the motor operating current waveform detected by the operating current detecting means. The difference between the ideal waveform and the operating current is calculated, and if the difference takes both positive and negative values within one cycle, it is determined that distortion has occurred.

  The output of the operating current detecting means for detecting the operating current of the electric motor is passed through a low-pass filter that attenuates the 11th order and higher of the fundamental frequency of the operating current and a high-pass filter that attenuates the 7th order and lower. What is necessary is just to determine with distortion, when the content rate of the 8th-11th order electric current which occupies for an operating current becomes 10% or less with respect to the whole effective value electric current.

  Further, it is the refrigeration cycle load that determines the load of the compressor 130, and since the distortion of the operating current waveform increases as the load increases, the distortion factor is calculated by the waveform distortion determination means 200, For example, when the distortion rate reaches a predetermined value, the load reducing means 210 decreases the discharge pressure of the compressor 130 by increasing the air volume of the condenser blower 145 or increasing the opening of the expansion valve 160. Reduce the load. Thereby, the abnormal stop of the compressor 130 can be prevented and the demagnetization phenomenon can be prevented.

  Further, as shown in FIG. 2, the value of the winding current for demagnetizing the permanent magnet decreases as the temperature of the permanent magnet increases. Therefore, a temperature sensor 190 for detecting the surface temperature of the compressor 130 is provided, and this signal is transmitted to the waveform distortion determination means 200. When the surface temperature increases to a predetermined value in relation to the surface temperature, for example, the compressor The judgment value of the operating current for shutting off the power switch 205 is reduced. Thereby, the reliability of the compressor 130 regarding temperature can be improved more.

  Furthermore, when the motor of the compressor 130 is driven by an inverter device, the current is cut off when the current becomes excessive, and is cut off by a few μsec after the current starts to rise because the power transistor of the inverter device is used. It is possible to cut off the current before the demagnetization even after the current increases. However, even in that case, the distortion of the operating current waveform is calculated, and in conjunction with the distortion rate, for example, when the distortion rate becomes a predetermined value, it is also used to cut off the current with the power transistor of the inverter device. More reliable. Further, if the air volume of the condenser blower 145 is controlled in relation to the distortion rate or the opening degree of the expansion valve 160 is controlled, the reliability can be further improved.

  Further, when the compressor power switch 200 is used, since it takes several milliseconds to open and close, the demagnetization phenomenon cannot be avoided as it is, and the load is increased in advance against the demagnetization phenomenon. It is effective to determine the length by the distortion of the operating current waveform.

  Furthermore, if the compressor 130 is a scroll compressor, the fluctuation of the compression torque is small, so that the load fluctuation on the motor is small. Therefore, when the distortion becomes a predetermined value, for example, in relation to the distortion, If the current is interrupted by the power transistor, the air volume of the condenser blower 145 is controlled, or the opening degree of the expansion valve 160 is controlled, the reliability can be improved.

The block diagram which shows one embodiment of this invention. The graph explaining the relationship between temperature and a demagnetizing current. The graph which shows the operating current waveform and rated frequency analysis result in the rated load by one Embodiment. The graph which shows the operating current waveform in the overload by one embodiment, and its frequency analysis result. The graph which shows the operating current waveform and frequency analysis figure at the time of a low voltage (180V) with respect to a rated voltage (200V). The graph which shows the operating current waveform and frequency analysis figure at the time of a high voltage (220V) with respect to a rated voltage.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 ... Permanent magnet, 110 ... Cage type | mold winding, 120 ... Rotor, 130 ... Compressor, 140 ... Condenser, 145 ... Condenser fan, 150 ... Evaporator, 160 ... Expansion valve, 170 ... Air conditioner, 180 ... Operating current detection means, 190 ... Temperature sensor, 200 ... Waveform distortion determination means, 210 ... Power supply switch for compressor.

Claims (10)

In a refrigeration cycle apparatus having a refrigeration cycle in which a compressor, a condenser, a condenser fan, an evaporator, and an expansion valve are sequentially connected,
An electric motor that drives the compressor, a squirrel-cage winding is formed on the outer periphery of the rotor, and permanent magnets magnetized on a plurality of poles are embedded inside the rotor;
A driving current detecting means for detecting an operating current of the motor,
The calculated distortion of driving current, when the value of the strain during operation the motor is a synchronous motor falls below a set value, the refrigeration cycle apparatus characterized by interrupting the power supply to the motor. 2. The refrigeration cycle apparatus according to claim 1, wherein the value of distortion of the operating current is a value based on a harmonic current component included in the operating current . In those described in claim 1, the refrigeration cycle apparatus characterized by controlling the air volume of the condenser blower in accordance with the distortion value of the operating current. In those described in claim 1, the refrigeration cycle apparatus characterized by controlling the opening of the expansion valve according to the distortion value of the operating current.   2. The refrigeration cycle apparatus according to claim 1, wherein a temperature sensor for detecting a surface temperature of the compressor is provided, and the set value is decreased when the surface temperature becomes high.   2. The refrigeration cycle apparatus according to claim 1, wherein the permanent magnet is magnetized in two poles, and the compressor is a scroll compressor. In those described in claim 1, in relation to the temperature of the strain value and the compressor of the driving current, and controlling the opening degree of the air volume or the expansion valve of the condenser blower refrigeration Cycle equipment. The said permanent magnet is magnetized to 2 poles, The said compressor is a scroll compressor, The said motor is driven with the inverter apparatus comprised by a power transistor, The electricity supply to the said motor is given Is performed by the power transistor, and the power transistor of the inverter device is cut off when the value of the distortion of the current becomes a set value or less . In a refrigeration cycle apparatus having a refrigeration cycle in which a compressor, a condenser, a condenser fan, an evaporator, and an expansion valve are sequentially connected,
An electric motor that drives the compressor, a squirrel-cage winding is formed on the outer periphery of the rotor, and permanent magnets magnetized on a plurality of poles are embedded inside the rotor;
An operating current detecting means for detecting an operating current of the electric motor,
A pulse signal corresponding to the presence or absence of a change in the operating current is generated, a value related to the distortion of the operating current is obtained based on the pulse signal, and a value related to the distortion is obtained while the motor is operating as a synchronous motor. A refrigeration cycle apparatus that cuts off the power supply to the electric motor when it becomes a set value or less . In a refrigeration cycle apparatus having a refrigeration cycle in which a compressor, a condenser, a condenser fan, an evaporator, and an expansion valve are sequentially connected,
An electric motor that drives the compressor, a squirrel-cage winding is formed on the outer periphery of the rotor, and permanent magnets magnetized on a plurality of poles are embedded inside the rotor;
A driving current detecting means for detecting an operating current of the motor,
A refrigeration cycle apparatus that controls the distortion of the operating current in association with at least one of the air volume of the condenser blower and the opening of the expansion valve.

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