JPH0695808B2 - Induction motor control circuit and control method - Google Patents

Description

TECHNICAL FIELD The present invention relates to a control circuit and a control method for an induction motor, and particularly to an induction in a refrigerator or the like to which a reciprocating compressor using the induction motor is applied. The present invention relates to a control circuit and control method for an electric motor.

“Prior Art” In electric appliances such as refrigerators and cooling / heating air conditioners that use induction motors in order to save power consumption, a certain amount of electric power has been conventionally used regardless of whether the motor is started or operated. The supply control circuit was configured.

These usually only utilize a thyristor to induce a stable current supply. For example, in a system in which a pair of thyristors are connected in parallel to a power supply transformer and the output thereof is applied to an electric motor, a positive voltage and a negative voltage force a speed change in the current while supplying a bidirectional current. As a result, an excessive voltage change rate is prevented and the speed of the electric motor is kept constant.

By the way, in Japanese Utility Model Publication No. 56-29752 (hereinafter referred to as Document 1), in a device that detects high load abnormal operation and low load abnormal operation of an electric motor, when only the power supply voltage fluctuates instead of abnormal operation. Discloses a technique of stopping the detection of the high load abnormal operation or the detection of the low load abnormal operation in order to prevent the device from malfunctioning due to the fluctuation of the power supply voltage.

Further, in Japanese Patent Application Laid-Open No. 57-9274 (hereinafter referred to as Document 2), a circuit for determining a voltage drop of a commercial power source is provided in an air conditioner, and the voltage drop of the commercial power source occurs when another electric device is starting. A technique is disclosed in which the start of the air conditioner is prohibited when the value is significant (for example, 5% or less of the steady value).

Further, in Japanese Patent Laid-Open No. 61-196720 (hereinafter referred to as Document 3), a fluctuation in power supply voltage is detected, and when the power supply voltage is other than an abnormally low voltage or an abnormally high voltage, the motor is energized and abnormally low. There is disclosed a technique of cutting off the electric power of a motor when a voltage or an abnormally high voltage is reached.

[Problems to be solved by the invention] However, in a reciprocating compressor that uses an induction motor, the motor can be started even at about -20% of the rated voltage in consideration of voltage fluctuations. As described above, when a constant voltage is applied regardless of whether the electric motor is started or operated, it induces a loss of electric power.In particular, the induction motor requires an overvoltage at the initial start, but the rated voltage after the start. -5% to 20% (80 to 95%) of electricity is required.

Further, the technique described in Document 1 merely stops the operation of the detection device when the voltage changes, and does not take any measures against the power loss.

Further, the technique described in Document 2 only prohibits the start of the air conditioner under a certain condition, and no measures are taken for the power loss in the air conditioner when the voltage changes.

In addition, the technique described in Document 3 only energizes and disconnects the motor (electric motor) when the power supply voltage fluctuates abnormally, and does not consider power loss during startup and operation.

"Means for solving problems" When considering such points, firstly, the microprocessor calculates so that the output is always constant by sensing the power supply voltage considering the voltage fluctuation with respect to the power loss. Secondly, the input of the compressor is controlled by controlling the input of the compressor, and secondly, the fluctuation voltage lost due to the difference between the starting power and the operating power is also processed by the microprocessor for a certain time after startup and the optimum value of the compressor input. Controlled as electric power, and thirdly, if there is an instantaneous power failure for a certain time or longer to prevent overloading of the compressor due to an instantaneous power failure, the startup of the compressor will be delayed for a fixed time and then restarted. I did it.

Therefore, the microprocessor according to the present invention controls the output voltage by programming, determines the presence / absence of a momentary power failure of 90 ms or more at the time of deviation PID of the proportional constant of the output voltage, and detects the analog voltage to detect the power supply voltage. The digital input is calculated and the above power supply voltage is -20% of the rated voltage.
If it is less than or equal to the rated voltage, the reset is displayed to request the power to be turned on again, while if it is 26% or more of the rated voltage, it is delayed for a predetermined time of 1 to 5 minutes and then the rated voltage or more is exceeded. It is determined whether or not

In addition, if the rated voltage is abnormal, the input voltage
If it is not more than 2.5%, if it is not more than that, phase control the power input to 90% or more for 1 to 3 minutes, then phase control 80% or more, and When it is 12.5% or more, the power input is phase-controlled for 80 to 80% or more for 0.2 to 3 minutes, and then the power input is controlled to a phase of about 60 to 90%.

On the other hand, if the rated voltage is + 12.5% or less of the rated voltage when abnormal, the phase control of 70 to 90% of the power input is
~ 3 minutes, 50 ~ 80% of power input phase control,
60% of the power input when the voltage is + 12.5% or less of the rated voltage
80% phase control is carried out for 0.1 to 2.5 minutes, and then 40 to 70% of the power input is controlled, but this is a classification control method by output voltage. If 12.5% or more and + 12.5% or less are judged, and if the power input is within the input signal range after the power input is phase-controlled for a predetermined time, proportional input deviation control is performed to Phase control of 40 to 95% is performed, and if not, a reset status is displayed or a failure is displayed.

In order to perform such an operation, the present invention calculates a power supply value using a sensing circuit having a power supply input sensing means for sensing a voltage of a power supply input, and a rated voltage for the power supply input as an analog / digital input to determine a predetermined cycle. A microprocessor for generating an output to control the motor, an oscillator circuit for generating an oscillation frequency of a constant cycle of a sawtooth wave using one or more outputs of the microprocessor, and applying this to the sensing circuit. Provided is a control circuit including an instantaneous power failure detection circuit having an instantaneous power failure detection means for detecting an instantaneous power failure, and a drive circuit for driving an electric motor by the output of a microprocessor.

Therefore, it is an object of the present invention to provide a control circuit for an induction motor that minimizes the loss of electric power generated during the startup and operation of the induction motor.

SUMMARY OF THE INVENTION An object of the present invention is to provide a method of controlling an induction motor that minimizes the loss of electric power generated during the start-up and operation of the induction motor by the arithmetic processing of a microprocessor.

[Examples] The following will describe the present invention in detail with reference to the accompanying drawings.

In FIG. 1, a power supply circuit according to the present invention is a plug 601.
A fuse 602, and a transformer 604 whose primary winding is connected in parallel with the varistor 603. This transformer 604
The AC terminals of the bridge rectifier circuit 605 are connected to both ends of the secondary winding of the rectifier circuit 605, and a smoothing capacitor C ₁ (having a predetermined delay time) and a resistor R ₁ are connected between the positive and negative terminals of the rectifier circuit 605. , And a precision regulator circuit is connected. This precision regulator circuit includes a precision regulator integrated circuit 606 and a constant voltage diode D ₁ and a capacitor C ₂ and a diode D ₂ connected in parallel with a smoothing circuit. Such a power supply circuit is connected to the power supply terminal V _{cc of the} microprocessor 700 and the ground terminal (not shown).

On the other hand, a resistor R ₁₈ and a capacitor C ₇ connected in series are connected to both ends of the primary winding of the transformer 604, and further an electric motor 402 is connected via a bridge rectifier circuit 401 described later.

The voltage fluctuation sensing circuit 100 includes a resistor R ₁ and a series resistor R 1 connected between the relay terminal of the precision regulator integrated circuit 606 and ground.
₂ and a resistor R ₃ , an operational amplifier 101 having an inverting terminal connected to the intermediate end of these series resistors and a non-inverting terminal to which an output from a sawtooth wave oscillation circuit 200 described later is applied, and the operational amplifier 101. NOT gate 1 which receives the signal of the resistor R ₄ connected in parallel with the output of and the rear end of the precision regulator circuit
It has 02 and.

Therefore, after the capacitor C ₁ is charged when power is applied, the voltage to the resistor R _3, i.e. When (here, V _R1 is the voltage applied to the resistor R ₁ ) is applied and the power supply voltage is changed, the voltage applied to the resistor R ₃ is also changed.

On the other hand, the non-inverting terminal (+) used as the reference terminal of the operational amplifier 101 receives the output of the sawtooth wave oscillation circuit 200 connected to the output terminals (P _{2 to} P ₅ ) of the microprocessor 700 described later. . This sawtooth wave oscillator 200 is a digital ramp, resistance trapezoid to generate a sawtooth wave by the order to output through the digital count output terminal of the microprocessor _{700 (P 2 ~P 5) (} R 5 ~R
₁₃ ) is connected to the resistors (R _{5 to} R ₁₃ ) and the capacitor C ₃ connected to this. Therefore, a sawtooth voltage having a predetermined cycle is applied to the operational amplifier 101.
This sawtooth voltage is as shown in FIG. 3 (C).

A the microprocessor 700 is inputted the output of the low level or high level of the operational amplifier 101 by fluctuations of the voltage applied to the resistor R ₃ through NOT gate 102, illustrated in FIG. 3 (B) When the power supply input to the resistor R ₃ is low as in the waveform, an output voltage with a relatively short pulse width is applied as in the initial waveform in FIG. 3 (A), and when the rated voltage is applied Since the waveform b in FIG. 3 (B) is applied, a pulse having a slightly longer pulse width like the intermediate waveform in FIG. 3 (A) is applied via the NOT gate 102 and is high. When the power supply voltage is applied, the c waveform of FIG. 3 (B) is applied, and a pulse having a long pulse width as shown in the final waveform of FIG. Applied to terminal P _{1 of} microprocessor 700.

In the microprocessor 700, the rated voltage input is applied from the precision regulator circuit without distinction between startup and operation as shown in FIG. 3 (D), but the power supply fluctuation is detected from the terminal P ₁ as described above. In this case, the phase of the power input is controlled depending on whether the power input is low or high.

That is, the output terminal P ₈ of the microprocessor 700 generates a pulse having a short pulse width like the initial waveform of FIG. 3 (E) when the power input is low, and a long pulse width when the power input is high. Generate a pulse of.

The microprocessor 700 also resets the reset terminal P ₉ when it detects −26% or more of the rated voltage in the power failure area.
To the enable state to turn on the light emitting diode LED ₁ connected to the resistor R ₁₉ to notify the user of a reset state or a failure.

An abnormal power supply detection circuit 300 for detecting an abnormal power supply input is connected to the interrupt terminal P ₇ of the microprocessor 700.

The abnormal power supply detection circuit 300 includes a determination circuit 301 that receives the discharge current of the capacitor C ₁ from a delay circuit composed of a resistor R ₁ and a capacitor C ₁ when the rated voltage becomes −26% or more or when a power failure occurs. To do. The discrimination circuit 301 can also be a comparator, which allows a low level signal to be applied to the microprocessor 700 via a resistor R ₁₅ when the signal from the capacitor C ₁ is applied. , With this, the microprocessor 700 is
_I will turn on ₁ . The symbols C ₄ and C ₅ are capacitors.

On the other hand, the motor drive circuit 400 that receives the output from the output terminal P _{8 of the} microprocessor 700 is connected to the transformer 604 of the power supply circuit as described above, but is connected to one end of the primary side of the transformer 604. A photo coupler 404 connected to the bridge circuit 401 via a resistor R _14, and a thyristor 403 controlled by the operation of the photo coupler 404.
It consists of and. The resistor R ₁₆ is a collector resistor,
The resistor R ₁₇ and the capacitor C ₆ are the gate ground cutoff device of the thyristor 403.

The thyristor 403 is applied to the electric motor drive circuit 400 by applying a pulse having a predetermined period such as the waveforms (E) and (G) of FIG. 3 to the photocoupler 404.
Is in the gate state while the pulse is at the “L” level and the third voltage is applied to the motor 402 connected to the bridge diode 401.
The power source having the waveform shown in FIG. 7F or the waveform shown in FIG. Therefore, when applying a low current, the motor 40
In case of 2, the power input time becomes long and the power input time becomes short when high current is applied.

The motor output sensing circuit 500 connected to the terminal P _{6 of the} microprocessor 700 is a well-known and well-known technique, and therefore its description is omitted here.

The microprocessor 700 of the present invention has the operation flow shown in FIGS. 2A and 2B so as to have such a configuration and operation.

FIGS. 2A and 2B respectively show a division control method by output voltage and a control method of deviation PID of the output proportional constant as a control method applicable according to the principle of the present invention. It is described in writing.

If there is a power input (step 10), it is judged from step 11 that an instantaneous power failure has occurred, but such an instantaneous power failure detection means is based on the predetermined charging time of the capacitor C ₁ as a reference, for example 90 ms or less. To determine if. If the momentary power failure time is not less than 90ms, the power input will be instructed.
Calculate the input at 12.

Next, in step 13, it is judged whether it is −26% or more of the rated voltage, and if it is not −26% or more, the reset state is set in step 14 and the light emitting diode LED ₁ is turned on.
Notify the user of a momentary power failure condition.

If it is more than -26% of the rated voltage, it continues to count in step 15 for a predetermined period of 1 to 5 and waits for the rated voltage to be applied in the current state. Next, it is judged whether or not the rated voltage is abnormal while confirming that the power is applied (step 16).
If there is an abnormality in the rated voltage, it is judged whether it is -12.5% or more of the rated voltage (step 17), and 90% or more of the power input phase control is performed for a predetermined period of 1 to 3 minutes. Or (stage
19), phase control of more than 80% of power input (step 20) 0.2
It will take about 3 minutes. On the other hand, when it is judged that it is + 12.5% or less of the rated voltage when an abnormality of the rated voltage occurs (step 18), 70-90% phase control of the power input is performed for 0.1-3 minutes. Toka (stage 21), power input 60
-80% phase control (step 22) is performed for a predetermined period of 0.1-2.5 minutes.

Therefore, in the above-mentioned steps in classification control by output voltage
More than 80% of the power input is phase controlled in step 23 via 19 and step 24 via step 20 above.
The phase control of 60 to 90 of the power supply input comes to be performed at 50 to 80% of the phase of the power supply input via the above step 21, and 40 to 70 of the power supply input via the above step 22. The phase is controlled to%. Also, in the PID control method, the microprocessor 700 receives the motor output detection signal at step 33 as shown in FIG. 2 (B) while controlling the phase of the power input, and the phase control signal is within the input signal range. To determine if there is (step 30).

If the detection signal is not within the input signal range, it will be in the reset state (step 14), and if it is within the input signal range, PID control will be performed and 40% to 95% phase control of the power input will be performed in steps 31 and 32 separately. Come to do.

[Advantages of the Invention] Accordingly, the present invention can automatically prevent the overvoltage of the induction motor, reduce the burnout of the applied device due to the overvoltage, and reduce the noise at the start when the overvoltage is applied. It can have a power saving effect of 10 to 30%.

[Brief description of drawings]

FIG. 1 is a detailed circuit diagram showing a control circuit of an induction motor according to the present invention, FIGS. 2A and 2B are flow chart diagrams showing the induction motor control of the present invention, and FIG. 3 is a waveform showing an operation of the present invention. It is a figure. 100 ... Voltage fluctuation sensing circuit, 101 ... Operational amplifier, 200 ...
… Sawtooth wave oscillator circuit, 300 …… Abnormal power supply detection circuit, 301 ……
Discrimination circuit (discrimination means), 400 ... Motor drive circuit, 402 ...
… Electric motor, 403 …… Thyristor (switching means), 4
04 …… Photo coupler, 700 …… Microprocessor, R1
...... Resistor (delay circuit), R2, R3 ...... Resistor (sensing means), C
1 ... Capacitor (delay circuit).

Claims (5)

[Claims] 1. A voltage fluctuation detection circuit (100) comprising a sensing means for sensing a fluctuation voltage due to a voltage fluctuation of an input power supply, and a value of the power supply is calculated by using a rated voltage for the input power supply as a digital input to determine a predetermined cycle. A microprocessor (700) for generating an output to control the induction motor (402), and one or more outputs from the microprocessor (700) as an oscillation frequency of a constant cycle of a sawtooth wave. Abnormal power supply detection circuit equipped with a sawtooth wave oscillation circuit (200) to be applied to 100) and a judgment means connected to the microprocessor (700) to detect an instantaneous power failure and an abnormal input power supply of -26% or less of the rated voltage. (300) and an electric motor drive circuit (400) for driving the induction motor (402) by the output of the microprocessor (700). circuit. 2. The voltage fluctuation detecting circuit (100), wherein the sensing means has one or more voltage dividing resistors (R2, R3) at its input terminal, and its output terminal has a voltage fluctuation more than a predetermined value. The control circuit for an induction motor according to claim 1, further comprising an operational amplifier (101) for detecting voltage fluctuations. 3. The determination means (301) of the abnormal power supply detection circuit (300) is connected to a delay circuit (R1, C1) for delaying the input of the power supply for a predetermined time, and is -26% or less of the rated voltage. The control circuit for an induction motor according to claim 1 or 2, wherein the discharge current of the delay circuit (R1, C1) is received in the case of a power failure to determine that there is a power failure. 4. A photocoupler (404) for operating the electric motor drive circuit (400) for a predetermined period by a pulse of a predetermined cycle output from the microprocessor (700).
And a switching means (403) that operates during a period other than the operation period of the photocoupler (404) to drive the induction motor (402) for a long period at a low input power source and at a high input power source. The induction motor control circuit according to any one of claims 1 to 3, wherein the induction motor (402) is driven for a short period. 5. A step (11) of determining whether or not the instantaneous power failure input is within a predetermined time, and a step (12) of detecting the power source input by the instantaneous power failure determination and calculating an input signal based on the detection signal. And the rated power supply judgment step (13) to judge whether it is more than -26% of the rated power supply, and the step where the power input is turned on again at the time of a power failure, such as not being more than -26% of the rated power supply, and the reset state. (14), if the rated power supply is -26% or more, wait for a predetermined time to induce the input of the rated power supply (15), and then check whether the rated voltage is abnormal or not. Judgment stage (1
6) If the rated voltage is not -12.5% or more, phase control of 90% or more of the power input is performed, and conversely, if the rated voltage is -12.5% or more, phase control of 80% or more of the power input is performed. , If the voltage is not less than + 12.5% of the rated voltage, phase control of 60-80% of the power input is performed. Conversely, if it is less than + 12.5% of the rated voltage, 70-90% of the power input is performed. And a step (17 to 22) for controlling the phase of the induction motor.