JP2006038432A - Compressor control method and refrigerant compression unit, and air conditioner and control method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a technique for enhancing loss that contributes to the heating of a refrigerant. <P>SOLUTION: A converter 2 receives a three-phase power from a three-phase power supply 1, and rectifies it and gives it to both the ends of a smoothing capacitor 3. A three-phase motor 5 is driven by allowing the inverter 4 to perform biphase modulation operation. The refrigerant 6 is compressed by a compressor 7 by the drive of the three-phase motor 5. By performing the biphase modulation operation, the iron loss of the motor 5 is increased while reducing the switching loss of the inverter without increasing current, thus the percentage loss of the motor 5 contributing to the heating of the refrigerant of all the loss is enhanced. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a technology for compressing a refrigerant, and particularly to a technology for compressing a refrigerant using a multiphase motor.

  When the air conditioner is operated for heating, since the refrigerant temperature and the temperature of the lubricating oil are low at the start-up, the load on the compressor is large. When the compressor is operated with a high operating capacity in this state, the lubricating oil stored in the compressor is discharged to the outside together with the discharged refrigerant. This is a so-called phenomenon of oil rising and causes poor lubrication.

  In order to avoid this oil rise, a technique for increasing the refrigerant temperature and the temperature of the lubricating oil has been proposed. For example, in Patent Document 1, the compressor is operated with a low operating capacity, and the temperature of the lubricating oil is raised by the heat generated by the motor windings. Further, in Patent Document 2, the phase of the motor current is shifted to prevent the rotation speed of the compressor from being limited by the DC voltage of the inverter due to the back electromotive force of the motor. Then, the motor current is increased to cause the coil to generate heat, which is absorbed by the refrigerant.

  A technique for performing two-phase modulation in relation to this case is exemplified in Patent Document 3.

JP 61-38365 A Japanese Patent No. 3021947 JP-A-56-115183

  However, if the current flowing in the motor coil is increased to generate heat, the loss in the inverter that controls the motor operation also increases. Since the loss of the inverter does not contribute to the heating of the refrigerant and the lubricating oil, the efficiency of the entire system is deteriorated.

  The present invention has been made to solve such a problem, and an object of the present invention is to provide a technique for increasing a loss that contributes to heating a refrigerant.

  A first aspect of the compressor control method according to the present invention includes a multiphase motor (5) to which multiphase power is supplied by an inverter (4), and compresses the refrigerant (6) by driving the multiphase motor. This is a method for controlling the compressor (7). The inverter performs two-phase modulation operation on the multiphase motor.

  A second aspect of the compressor control method according to the present invention is the compressor control method according to the first aspect, wherein the inverter (4) is connected to another multi-phase power source (1) by a converter (22). Is supplied with DC power that is rectified by two-phase modulation.

  A third aspect of the compressor control method according to the present invention is the compressor control method according to the first aspect or the second aspect, wherein the converter (22) performs a boosting operation.

  A fourth aspect of the compressor control method according to the present invention is the compressor control method according to the first aspect, wherein the inverter (4) is connected to another multi-phase power source (1) by a diode bridge (21). ) Is rectified.

  According to a fifth aspect of the compressor control method of the present invention, there is provided the compressor control method according to the first to fourth aspects, wherein the inverter (4) supplies the multiphase motor (5). The current is increased by shifting the phase of the current.

  A first aspect of the refrigerant compressor according to the present invention includes an inverter (4), a multiphase motor (5) to which multiphase power is supplied by the inverter, and a refrigerant (6) driven by the multiphase motor. And a compressor (7) for compression. The inverter performs two-phase modulation operation on the multiphase motor.

  A second aspect of the refrigerant compression device according to the present invention is the refrigerant compression device according to the first aspect, wherein the other multiphase power source (1) is rectified by two-phase modulation with respect to the inverter (4). A converter (22) for supplying DC power is further provided.

  A third aspect of the refrigerant compression apparatus according to the present invention is the refrigerant compression apparatus according to the first aspect or the second aspect, wherein the converter (22) performs a boosting operation.

  A refrigerant compressor according to a fourth aspect of the present invention is the refrigerant compressor according to the first aspect, wherein the inverter (4) is connected to another multiphase power source (1) by means of a diode bridge (21). Rectified DC power is supplied.

  A fifth aspect of the refrigerant compression apparatus according to the present invention is the refrigerant compression apparatus according to the first to fourth aspects, wherein the inverter (4) has a current supplied to the multiphase motor (5). The current is increased by shifting the phase.

  The control method of the air conditioner concerning this invention controls the air conditioner using the said compressor using the compressor control method concerning the 1st thru | or 5th aspect.

  The air conditioner according to the present invention uses the refrigerant compressor according to the first to fifth aspects.

  According to the first aspect of each of the compressor control method and the refrigerant compressor according to the present invention, compared with the case of performing normal multiphase operation, the iron loss is increased without increasing the copper loss of the motor, In addition, the loss in the inverter can be reduced. Therefore, the loss contributing to heating the refrigerant can be increased. In addition, the cost of the inverter can be reduced. If the inverter loss is the same, the output of the multiphase motor can be increased to increase the maximum capacity during heating operation. This contributes to faster heating start-up. If the inverter loss is the same, the switching frequency can be increased, and the noise in the audible range can be reduced.

  According to the second aspect of each of the compressor control method and the refrigerant compressor according to the present invention, the loss of the converter can be reduced, and the cost of the converter can be reduced.

  According to the third aspect of the compressor control method and the refrigerant compressor according to the present invention, the effect of claim 1 can be further enhanced.

  According to the fourth aspect of each of the compressor control method and the refrigerant compressor according to the present invention, it is possible to reduce the loss of the converter and thus to reduce the total loss.

  According to the fifth aspect of each of the compressor control method and the refrigerant compressor according to the present invention, the effect of heating the refrigerant can be enhanced by increasing the copper loss.

  The air conditioner control method according to the present invention can enjoy the effects of the compressor control methods according to the first to fifth aspects.

  The air conditioner according to the present invention can enjoy the effects of the refrigerant compression device according to the first to fifth aspects.

  FIG. 1 is a block diagram showing a configuration of a refrigerant compression apparatus to which a compressor control method according to the present invention can be applied. The three-phase power source 1 applies a three-phase AC voltage to the converter 2. The converter 2 applies a DC voltage obtained by rectifying the three-phase AC voltage to both ends of the smoothing capacitor 3. The inverter 4 converts the voltage across the smoothing capacitor 3 into a three-phase AC voltage and applies it to the three-phase motor 5.

  The compressor 7 has a three-phase motor 5 that is driven to compress the refrigerant 6. Such a compressor 7 is employed in an air conditioner.

  In the present embodiment, a description will be given by taking three phases as an example of a multiphase power source or a multiphase motor, but the present invention can also be applied in a larger number of phases.

  FIG. 2 is a circuit diagram illustrating the structure of the diode bridge 21 applicable as the converter 2 in the present invention. The diode bridge 21 includes diodes 201 and 202, diodes 203 and 204, and diodes 205 and 206 that are connected in series corresponding to each phase of the three-phase power source. The cathodes of the diodes 201, 203, 205 are commonly connected to the positive side of the smoothing capacitor 4, and the anodes of the diodes 202, 204, 206 are commonly connected to the negative side of the smoothing capacitor 4. The anode of the diode 201 and the cathode of the diode 202 are connected in common, and the first phase voltage of the three-phase power source 1 is supplied. The anode of the diode 203 and the cathode of the diode 204 are connected in common, and the second phase voltage of the three-phase power source 1 is supplied. The anode of the diode 205 and the cathode of the diode 206 are connected in common, and the third phase voltage of the three-phase power source 1 is supplied.

  FIG. 3 is a circuit diagram illustrating the structure of the PWM converter 22 applicable as the converter 2 in the present invention. The PWM converter 22 has a configuration in which six insulated gate bipolar transistors (hereinafter referred to as “IGBT”) as switching elements and a reactor group 210 are added to the diode bridge 21. The IGBTs 211 to 216 are connected in antiparallel with the diodes 201 to 206, respectively. Here, the reverse parallel indicates that the diode and the IGBT are connected in parallel so that the forward directions are opposite to each other. With this connection, the diodes 201 to 206 function as freewheeling diodes in the switching operation of the IGBTs 211 to 216.

  Reactor group 210 is provided between each phase of three-phase power supply 1 and each phase input of PWM converter 22 (a connection point of a pair of diodes connected in series corresponding to each phase).

  The diode bridge 21 is easy to configure as compared with the PWM converter 22 and is desirable in that the loss in the converter 2 can be reduced because the switching loss of the IGBTs 201 to 206 and the loss in the reactor group 210 do not occur. However, the PWM converter 22 can perform a boosting operation in which the voltage across the smoothing capacitor 3 is higher than the interphase voltage of the three-phase power supply 1. As will be described later, the higher the both-end voltage, the higher the ratio of the iron loss of the three-phase motor 5 to the loss in the inverter 4 and the loss in the converter 2 is desirable.

  The inverter 4 has a configuration in which the reactor group 210 is removed from the PWM converter 22. Both-end voltages are input between the cathodes of three diodes (corresponding to the diodes 201, 203, and 205 in FIG. 3) and the three diodes (corresponding to the diodes 202, 204, and 206 in FIG. 3). AC is output from the connection point of a pair of diodes connected in series corresponding to.

First embodiment.
In the present embodiment, a technique for increasing the loss of the three-phase motor 5 while reducing the loss in the inverter 4 is provided. Thereby, the ratio which the loss of the three-phase motor 5 contributes when heating the refrigerant 6 can be increased.

  As described above, it was confirmed that in order to increase the ratio of the iron loss, the inverter 4 may perform the two-phase control operation of the motor 5. This will be described using data.

  FIG. 4 is a diagram showing the loss of each part when the peak value of the phase voltage of the three-phase power source 1 is approximately 500 V, in the case of the normal three-phase control operation and the case of the two-phase control operation. FIG. 4A shows the loss in the inverter 4, and FIG. 4B shows the loss in the motor 5. A common unit is adopted for these numerical values.

  In addition to the case where the voltage across the smoothing capacitor 3 is 498 V, the case where the voltage is boosted to 650 V and 730 V by the boosting operation of the PWM converter 22 is described. However, here, the output of the three-phase motor 5 is set to an equal value, and the switching frequency (carrier frequency) of the inverter 4 and the PWM converter 22 is individually fixed.

  From FIG. 5A, it can be seen that the loss in the inverter 4 does not substantially depend on the voltage at both ends in the two-phase control operation, but increases as the voltage at both ends increases in the three-phase control operation. Further, the loss in the inverter 4 is smaller in the two-phase control operation than in the three-phase control operation. This is probably because the number of switching times of the IGBTs 211 to 216 per cycle is smaller in the two-phase control operation than in the three-phase control operation (although the carrier frequency is equal).

  Therefore, from the viewpoint of reducing the loss of the inverter 4, the two-phase control operation is preferable to the three-phase control operation, and the effect is more remarkable as the voltage at both ends is increased (52/69> 53/74> 53/75). Therefore, the cost of the inverter 4 can be reduced, and conversely, the loss of the inverter 4 is given a margin, and there is room for increasing the output of the three-phase motor 5.

  From FIG. 5B, the copper loss of the motor 5 is the same in both the three-phase control operation and the two-phase control operation, and decreases as the voltage at both ends increases (124> 95> 85). However, the iron loss of the motor 5 is larger in the two-phase control operation than in the three-phase control operation, and the ratio increases as the voltage at both ends increases (218/210 <330/308 <417/360). . Therefore, from the viewpoint of increasing the loss of the motor 5 and generating heat, the two-phase control operation is preferable to the three-phase control operation, and the effect is more remarkable as the voltage across the both ends is increased. The same applies to the amount of heat given to the lubricating oil (not shown) of the compressor 7. Therefore, inconveniences such as oil rising can be effectively avoided.

  Further, if the loss of the inverter 4 is the same, the output of the three-phase motor 5 can be increased, and the maximum capacity during the heating operation of the air conditioner employing the compressor 7 can be increased. This contributes to faster heating start-up. Further, if the loss of the inverter 4 is the same, the switching frequency can be increased, and the noise in the audible range can be reduced.

Second embodiment.
In the present embodiment, a technique for reducing loss in converter 2 is provided. Thereby, the cost of the converter 2 can be reduced. Further, the loss of the converter 2 is given a margin, and there is room for increasing the output of the three-phase motor 5. Since the PWM converter 22 has the same configuration as that of the inverter 4 except that the reactor group 210 is provided, the PWM converter 22 can be operated in two phases similarly to the inverter 4. Therefore, in this embodiment, the PWM converter 22 is employed as the converter 2.

  FIG. 5 is a diagram showing the loss of each part when the peak value of the phase voltage of the three-phase power supply 1 is approximately 500 V, in the case of the normal three-phase control operation and the case of the two-phase control operation. 2A shows the loss in the reactor group 210, FIG. 2B shows the loss in the PWM converter 22 excluding the reactor group 210, and FIG. 2C shows the loss in the entire PWM converter 22. FIG. These data depend on the output of the three-phase motor 5 on which the data of FIG. 4 depends and the switching frequency (carrier frequency) of the inverter 4 and the PWM converter 22, and the units common to those in FIG. 4 are adopted for the numerical values.

  According to FIG. 5A, like the copper loss of the motor 5, the copper loss of the reactor group 210 is the same in the three-phase control operation and the two-phase control operation. However, the value 27 is taken without depending on the voltage between both ends. On the other hand, similarly to the iron loss of the motor 5, the iron loss of the reactor group 210 is larger in the two-phase control operation than in the three-phase control operation, and the tendency becomes more prominent as the voltage at both ends is increased. Therefore, the loss in the PWM converter 22 is disadvantageous because it is larger in the two-phase control operation than in the three-phase control operation when limited to the reactor group 210.

  However, according to FIG. 5B, the loss in the PWM converter 22 excluding the reactor group 210 is smaller in the two-phase control operation than in the three-phase control operation. As shown in FIG. 5C, the loss in the entire PWM converter 22 is smaller in the two-phase control operation than in the three-phase control operation.

  As described above, not only the inverter 4 but also the PWM converter 22 is subjected to two-phase control operation, and a voltage at both ends is obtained by a rectifying operation, so that a loss in the converter 2 can be given a margin. This increases the room for increasing the output of the three-phase motor 5.

Third embodiment.
If the diode bridge 21 is employed as the converter 2, there is no switching loss of the reactor group 210 and IFBTs 211 to 216. Therefore, it is desirable in terms of reducing the loss of the converter 2 and reducing the overall loss.

Fourth embodiment.
A method of shifting the current phase as in Patent Document 2 can also be applied to the present invention. FIG. 6 shows the loss of each part when the peak value of the phase voltage of the three-phase power supply 1 is approximately 500 V, in the case of normal three-phase control operation and in the case of performing phase control of current in three-phase control operation. FIG. 6 is a diagram showing a comparison between a case of two-phase control operation and a case of two-phase control operation and also performing phase control of current. FIGS. 9A and 9B show the case where the both-end voltages are 498V and 650V, respectively.

  The two-phase control operation shown in FIG. 6 shows a case where not only the inverter 4 but also the PWM converter 22 is operated in a two-phase control operation. Therefore, the numerical values in the column labeled “two-phase” are the data of FIG. 4 for the loss of the inverter 4 and the motor 5, and the values of the loss of the reactor group 210 and the PWM converter 22 (excluding the reactor group 210) are as shown in FIG. Each of these data has been posted.

  These data depend on the output of the three-phase motor 5 on which the data of FIGS. 4 and 5 depend, and on the switching frequency (carrier frequency) of the inverter 4 and the PWM converter 22, and the numerical values are the same as those in FIG. Is done.

  Regardless of the three-phase control operation or the two-phase control operation, if the current phase control is performed, the current can be increased, the copper loss of the motor can be increased, and the refrigerant can be heated. However, the increase in current also increases the semiconductor element loss (the sum of the loss of the PWM converter 22 (excluding the reactor group 210) and the loss of the inverter 4).

  Therefore, when boosted, the two-phase control operation can increase the ratio of the loss of the motor 5 to the total loss as compared with the case where the current phase control is performed in the three-phase control operation. For example, when the voltage at both ends is 498 V ((a) in the figure), the ratio is 355/661 = 0.537 in the case of performing phase control of current in the three-phase control operation, whereas the second embodiment At 342/653 = 0.524, it becomes smaller. However, when the voltage between both ends is 650 V ((b) in the figure), the ratios are 419/894 = 0.469 and 425/760 = 0.559, respectively, and the two-phase control operation is more advantageous.

  Even in the case of current phase control, the semiconductor element loss can be reduced in the case of performing the two-phase control operation than in the case of performing the three-phase control operation (286> 216 at both ends voltage 498V, 373 at both ends voltage 650V). > 267). Therefore, the cost of the inverter 4 and the PWM converter 22 can be reduced. Conversely, if the semiconductor element losses are equal, the output of the three-phase motor 5 can be increased, and the maximum capacity during the heating operation of the air conditioner employing the compressor 7 can be increased.

It is a block diagram which shows the structure of the refrigerant compressor which can apply the compressor control method concerning this invention. 3 is a circuit diagram illustrating the structure of a diode bridge 21. FIG. 3 is a circuit diagram illustrating the structure of a PWM converter 22. FIG. It is a figure which shows the effect of the 1st Embodiment of this invention. It is a figure which shows the effect of the 2nd Embodiment of this invention. It is a figure which shows the effect of the 3rd Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Three-phase power supply 2 Converter 21 Diode bridge 22 PWM converter 3 Smoothing capacitor 4 Inverter 5 Motor 6 Refrigerant 7 Compressor

Claims (12)

A method for controlling a compressor (7) having a multiphase motor (5) to which multiphase power is supplied by an inverter (4), and compressing the refrigerant (6) by driving the multiphase motor,
The compressor control method, wherein the inverter performs a two-phase modulation operation on the multiphase motor.   The compressor control method according to claim 1, wherein the inverter (4) is supplied with a DC power source obtained by rectifying another multi-phase power source (1) by two-phase modulation by a converter (22).   The compressor control method according to any one of claims 1 and 2, wherein the converter (22) performs a boosting operation.   The compressor control method according to claim 1, wherein the inverter (4) is supplied with a DC power source obtained by rectifying another multiphase power source (1) by a diode bridge (21).   The compressor control method according to any one of claims 1 to 4, wherein the inverter (4) increases the current by shifting a phase of a current applied to the multiphase motor (5). An inverter (4);
A multiphase motor (5) to which multiphase power is supplied by the inverter;
A compressor (7) that compresses the refrigerant (6) by driving the multiphase motor;
The inverter performs a two-phase modulation operation of the multiphase motor. Converter (22) for supplying a DC power source obtained by rectifying another multi-phase power source (1) by two-phase modulation to the inverter (4)
The refrigerant compressor according to claim 6, further comprising:   The refrigerant compressor according to any one of claims 6 and 7, wherein the converter (22) performs a boosting operation.   The refrigerant compression apparatus according to claim 6, wherein the inverter (4) is supplied with a DC power source obtained by rectifying another multiphase power source (1) by a diode bridge (21).   The refrigerant compressor according to any one of claims 6 to 9, wherein the inverter (4) increases the current by shifting a phase of a current applied to the multiphase motor (5).   An air conditioner control method for controlling an air conditioner using the compressor using the compressor control method according to any one of claims 1 to 5.   An air conditioner using the refrigerant compressor according to any one of claims 6 to 10.

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