JP2003106617A - Control method of compressor motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a control method of a compressor motor free from the generation of an out-of-control state. SOLUTION: In this control method of the compressor motor 14 used in a case when the load is a compressor, and the operation is transferred from a steady operation mode for performing high-speed operation with frequency F1, and a low-speed operation mode with low frequency F3, an intermediate frequency F2 between the frequency F1 and the frequency F3 is determined, the frequency is lowered at a high speed from the frequency F1 to the frequency F2, the frequency is lowered at a low speed from the frequency F2 to the frequency F3 to switch a rotating speed of the compressor motor 14 to a low-speed operation in a short time while preventing the excess phenomenon of DC current.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for controlling a compressor motor which is used as a rotary power source for a compressor of an air conditioner and which is driven by an inverter by PWM control.

[0002]

2. Description of the Related Art Conventionally, an inverter-controlled compressor motor has been used as a compressor motor for an air conditioner in terms of efficiency and noise. The rotor of this compressor motor is mainly composed of a permanent magnet having magnetic poles around it, and an electromagnet having a plurality of magnetic poles is used for the outer stator. The magnetic poles are switched by passing PWM-modulated alternating current to the stator, and the rotating torque is applied to the rotor. Is being generated. Since this compressor motor rotates on the same principle as an AC synchronous motor, control is performed to gradually shift the drive frequency from low frequency to high frequency from the start to the steady operation mode. There is. The compressor motor is controlled so as to reduce the frequency according to the current of the inverter circuit and / or the compressor discharge temperature.

[0003]

However, as a method for gradually increasing or decreasing the frequency of the inverter, conventionally, the frequency is increased or decreased at a constant rate (for example, 1 Hz / second). When the speed is reduced, the rotor is decelerated while the pressure difference between the compressor suction port and the discharge port is large, and the motor is overloaded, and the DC current may rise to the stop level and the compressor may stop. Of course, if the frequency is lowered at a sufficiently slow speed, the above DC current excessive phenomenon disappears, but there is a problem that the response to the current of the inverter circuit and / or the limitation of the compressor discharge temperature is delayed. The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a method for controlling a compressor motor in which the above-described increase in DC current does not occur.

[0004]

According to a first aspect of the present invention, there is provided a method of controlling a compressor motor according to the first aspect of the invention, wherein a load is a compressor and a steady operation mode in which a high speed operation is performed at a frequency F1 to a low speed at a low frequency F3. In a method of controlling a compressor motor used when shifting to an operation mode, a frequency F that is intermediate between the frequencies F1 and F3 described above.
2 is set, the frequency is lowered at a high speed from the frequency F1 to the frequency F2, and the frequency is lowered at a low speed from the frequency F2 to the frequency F3, and the rotation speed of the compressor motor is
The low-speed operation is switched in a short time so as not to cause an excessive phenomenon of DC current. If a compressor is used as a load, the frequency reduction rate will be the same as that of frequency F1 to frequency F3.
However, if the frequency is reduced at the same reduction ratio even if the frequency reduction ratio does not cause the DC current excessive phenomenon in the high frequency region, the DC current excessive phenomenon in the low frequency region is likely to occur. Has been confirmed by experiments. Therefore, from frequency F1 to frequency F2, D
The frequency is lowered at the reduction ratio (R1) in the high-speed range that does not cause an excessive phenomenon of the C current, and the frequency is changed from the frequency F2 to the frequency F3.
Until then, the frequency is lowered at a reduction ratio (R2) in the low speed range that does not cause an excessive phenomenon of DC current. In this case,
Although R1 is larger than R2 in the reduction ratio, it is possible to decelerate faster from the frequency F1 to the frequency F2 by lowering with R2.

A control method for a compressor motor according to a second aspect of the present invention is the control method for a compressor motor according to the first aspect, wherein the frequency F2 is (F1-F
3) / 3 to (F1-F3) 2/3 is preferable. When the frequency change rate is slow, the DC current does not become excessive. However, it takes time to deteriorate the operation efficiency, and it is preferable to conduct an experiment to select the optimum value. Frequency change speed used for driving (1 Hz / in this embodiment)
It is preferably about 1/3 to 2/3 of the second). And the third
The control method for the compressor motor according to the invention is the same as the control method for the compressor motor according to the first invention, wherein the frequency F2 is predetermined such as (F1) / 2. The intermediate frequency F2 is also preferably obtained by experiment, but if the preload condition of the compressor is known, it can be calculated from the torque.

A compressor motor control method according to a fourth aspect of the present invention is a compressor motor control method in the case where a load is a compressor and decelerates from a steady operation mode, the compressor motor is decelerated by a steady frequency change. In this case, the intermediate frequency F2 at which the DC current starts to increase is calculated, and when the deceleration operation is performed in the frequency region exceeding the intermediate frequency F2, the steady state (that is, the high speed reduction ratio R1) When the deceleration operation is performed with a frequency change and the deceleration operation is performed in the frequency region equal to or lower than the intermediate frequency F2, the deceleration operation is performed at a change speed (R2) smaller than the steady frequency change. The load of the compressor also depends on the pressure difference between the suction port and the discharge port of the compressor, but if the change speed is small, the delay of the pressure change can be dealt with, so that the load of the motor is reduced and the increase of the DC current can be prevented. A compressor motor control method according to a fifth aspect of the present invention is the compressor motor control method according to the fourth aspect of the present invention, wherein the frequency change speed when the deceleration operation is performed in the frequency region of the intermediate frequency F2 or less. Is in the range of 1/3 to 2/3 of the steady frequency change.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION Next, referring to the attached drawings, an embodiment in which the present invention is embodied will be described to provide an understanding of the present invention. Here, FIG. 1 is a flow chart of a method for controlling a compressor motor according to an embodiment of the present invention, FIG. 2 is a block diagram of a control device for the compressor motor, and FIG. 3 is a graph for explaining an operating state.

As shown in FIG. 2, a compressor motor control apparatus 10 to which a compressor motor control method according to an embodiment of the present invention is applied includes a rectifier circuit 11 for converting an alternating current of a commercial power source into a direct current, and a rectifier circuit. An inverter 12 for converting the direct current converted by 11 into three-phase alternating current;
And a control unit 13 including a microcomputer that sends programmed commands to these. The inverter 12 has a well-known structure, has a power transistor inside, and sequentially switches the power transistors to send the PWM-controlled output to the compressor motor 14. The compressor motor 14 is used in an air conditioner, and has a compressor that compresses a refrigerant as a load.

The control unit 13 has a microcomputer chip inside, and is internally operated by a pre-programmed instruction by an input from a temperature detection sensor provided in the indoor unit or a discharge temperature detection sensor of the compressor (neither is shown). A PWM control signal is created and sent to the inverter 12. As the rectifier circuit 11, a normal bridge rectifier circuit is used. When the compressor motor 14 is started from the stopped state, the control unit 13 creates a PWM control signal of ultra-low frequency and sends the low-voltage low-frequency alternating current to the compressor motor 14 in addition to the inverter 12. As a result, the compressor motor 14 starts rotating. When the output from the inverter 12 reaches 10 Hz, the compressor motor 14 starts stable rotation, and from there, the rate of change of 1 Hz / sec (constant speed change rate or high speed change rate R1) is raised to the steady operating frequency. . As a result, as shown in FIG. 3, the compressor motor 14 can perform the steady operation of the compressor, which is a load.

Next, when the load is abnormal and an excessive current flows through the compressor motor 14, it is necessary to reduce the rotation of the compressor motor 14 to reduce the current of the compressor motor 14. In this case, how much to reduce is set in advance from past data, and now when the frequency F1 in the steady operation mode is 120 Hz and the operation is switched to the frequency F3 (30 Hz) operation in the low speed operation mode,
This will be described with reference to the flowchart of FIG. In this case, the intermediate frequency F2 is 50 Hz. Even if the intermediate frequency F2 has a negative pressure on the compressor motor 14 due to the residual pressure of the compressor, if the frequency changing speed is set to 0.5 Hz, the compressor motor 14
Is a frequency that does not cause an excessive phenomenon of DC current. The intermediate frequency F2 varies depending on the compressor motor 14, the compressor connected to the compressor motor 14, and the rate of change of the frequency during deceleration, but is usually (F1-F3) × 1/3
The range is 2/3.

As shown in FIG. 1, there is an instruction to decelerate the compressor motor 14 due to excessive current (step S1).
Then, it is confirmed whether or not the operating frequency is equal to or lower than the intermediate frequency F2 (50 Hz) (step S2), and if it exceeds 50 Hz, the frequency change speed (1 Hz / sec) of the high-speed change ratio R1 as it is. ) Is maintained (step S
5). Then, when the operating frequency becomes 50 Hz or less in step S2, it is confirmed that it is in the lowering direction (step S3), and it is switched to 0.5 Hz / sec which is the low speed frequency change ratio R2 (step S4). . As a result, as shown in FIG. 3, the speed of the compressor motor 14 can be reduced without causing an excessive phenomenon of the DC current, and it is confirmed that the predetermined low speed frequency F3 has been reached (step S6), and the process ends. If the predetermined low speed frequency F3 is not reached, the operation is repeated by repeating the above steps to shift the compressor motor 14 to the low speed frequency F3 operation without causing an excessive phenomenon of DC current.
The step S3 can be omitted because the deceleration instruction is given in the step S1. When the calculation of the microcomputer program is set with a frequency accuracy that can be easily calculated in 1-byte units, R2 is 1/3 to 2/3 of R1, and preferably 1/2 to 2/3 is a good result.

If the speed of the compressor motor 14 is gradually reduced in order to reduce the current of the compressor motor 14 to a predetermined value or less, step S
The control may be performed by setting 6 as "whether the current has become equal to or lower than a predetermined current". In this case, if the current of the compressor motor 14 drops even if the intermediate frequency F2 is exceeded, the operation is performed while maintaining that state. Although the above embodiment has been described with respect to the case of an air conditioner, the present invention can be applied to any device using a compressor (for example, a refrigerator or the like).

[0013]

As is apparent from the above description, in the compressor motor control method according to the first to fifth aspects, when the compressor motor is switched to the low speed operation mode, the intermediate frequency F2 is set and the intermediate frequency F2 is set. Since the operation is performed with a high frequency change at a frequency exceeding the frequency F2 of the above, and the operation is performed at a frequency change speed lower than the intermediate frequency F2, the operation can be performed without causing an excessive phenomenon of the DC current in the compressor motor. Particularly, in claims 1 to 3, it is possible to reach the low speed operation mode from the high speed operation mode in a relatively short time without causing an excessive phenomenon of the DC current. Further, in the compressor motor control method according to the fourth and fifth aspects, it is possible to switch to a low speed operation in which an increase in current is suppressed in a relatively short time. Further, in the compressor motor control method according to the fifth aspect, it is possible to obtain the effect of simplifying the microcomputer program.

[Brief description of drawings]

FIG. 1 is a flowchart of a method for controlling a compressor motor according to an embodiment of the present invention.

FIG. 2 is a block diagram of a control device for the compressor motor.

FIG. 3 is a graph illustrating an operating state.

[Explanation of symbols]

10: Control device for compressor motor, 11: Rectifier circuit, 12: Inverter, 13: Control unit, 14: Compressor motor

Continued front page    F term (reference) 3L060 AA01 AA08 CC10 CC19 DD07                       EE04                 5H560 AA02 BB04 BB12 EB01 JJ02                       RR07 TT15                 5H576 AA10 BB09 DD07 FF04 FF07                       FF08 HB01 JJ03 MM02

Claims (5)

[Claims] 1. The load is a compressor, and the frequency F
From the steady operation mode in which high speed operation is performed at 1, low frequency F3
In the control method of the compressor motor used when shifting to the low speed operation mode in (1), a frequency F2 intermediate between the frequencies F1 and F3 described above is determined, and the frequency is lowered at a high speed from the frequency F1 to the frequency F2. A method of controlling a compressor motor, characterized in that the frequency is lowered at a low frequency up to a frequency F3, and the rotational speed of the compressor motor is switched to a low speed operation in a short time without causing an excessive phenomenon of DC current. 2. The method for controlling a compressor motor according to claim 1, wherein the frequency F2 is (F1-F3) /
The method for controlling a compressor motor is in the range of 3 to (F1-F3) 2/3. 3. The method of controlling a compressor motor according to claim 1, wherein the frequency F2 is predetermined. 4. A method of controlling a compressor motor in the case where a load is a compressor and decelerating from a steady operation mode, an intermediate frequency at which a DC current starts to increase when the compressor motor is decelerated by a steady frequency change. When F2 is set and the deceleration operation is performed in the frequency range exceeding the intermediate frequency F2, the steady frequency change is performed, and the deceleration operation is performed in the frequency range of the intermediate frequency F2 or lower. In this case, the method for controlling a compressor motor is characterized in that deceleration operation is performed at a change speed smaller than the steady frequency change. 5. The method of controlling a compressor motor according to claim 4, wherein the speed of frequency change when the deceleration operation is performed in the frequency region of the intermediate frequency F2 or less,
A method of controlling a compressor motor, characterized in that it is in the range of 1/3 to 2/3 of the steady frequency change.