JPS6237092A - Drive system of single phase induction type electric motor - Google Patents

Abstract

PURPOSE:To start a motor by high torque, and to variable-speed drive the motor by low torque by using an auxiliary coil by connecting an inverter to the auxiliary coil and shifting the currents of the auxiliary coil by 1/2pi with regard to the currents of a main coil. CONSTITUTION:The phase of currents is shifted by 1/2pi by a main coil 3 and an auxiliary coil 11until the number of revolution of an electric motor 1 reaches the number of revolution n0 corresponding to power frequency f0, and the motor is driven by high torque. When the number of revolution of the motor 1 reaches n0 and the motor 1 is driven by the number of revolution n0 corresponding to the frequency f0 of the currents of the main coil, the supply of the currents of the auxiliary coil by an inverter circuit 9 is interrupted, and the motor 1 is driven only by the main coil 3. When the motor 1 is variable-speed driven, the main coil 3 is detached from a power supply by a switching member 5, and only the auxiliary coil 11 is one-phase driven while the frequency of a power supply for the auxiliary coil is varied by the inverter circuit 9.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a drive system for a single-phase induction electric motor (hereinafter referred to as an electric motor).

[Prior art] In a conventional electric motor, a current relay and a capacitor are connected in series to an auxiliary coil connected in parallel to the main coil, and when the electric motor starts rotating, J3 is connected to the main coil and the main coil current. On the other hand, by driving the auxiliary coil in two phases to which auxiliary coil currents whose phases are shifted by the capacitor are supplied, a rotating magnetic field is formed and the starting torque is 1q. When the electric motor reaches a required rotational speed, the current relay opens due to a decrease in the auxiliary coil current, and the electric motor is rotationally driven in one phase by only the main coil.

This provides the required starting torque.

[Problems to be Solved by the Invention] However, in the above drive method, the impedance of the auxiliary coil changes as the electric motor rotates, and the capacitor ensures that the phase of the auxiliary coil current with respect to the main coil current is equal to 1. /2π deviation was difficult, and an ideal rotating magnetic field could not be formed. As a result, the electric motor could not be started to rotate with a high starting torque. The above drawback is that the main coil and the auxiliary coil are controlled by an inverter, and the auxiliary coil current is activated with a phase shift of 1/2π with respect to the main coil current. When it is desired to variable speed control the electric motor to a required rotational speed, the main coil and/or the auxiliary coil are controlled by an inverter to drive the electric motor at variable speed. However, the main coil has a higher occupation rate than the auxiliary coil, but in applications that do not require a large amount of rotational torque after reaching the required number of rotations, the main coil with a high occupation rate can be used to control the electric motor. The economic efficiency was poor when driving.

[Object of the Invention] In view of the above-mentioned conventional drawbacks, the object of the present invention is to provide an auxiliary coil that can be started with high torque and that has a low occupation rate after the required rotation speed has been reached. An object of the present invention is to provide a drive system for a single-phase induction electric motor that can be used to drive at variable speeds with low torque.

[Means for Solving the Problems] Therefore, the present invention provides a single-phase induction electric motor that rotates as a main coil and an auxiliary coil are driven, in which a main coil current is supplied when the electric motor is started. After obtaining a starting l·lux by driving the main coil and an auxiliary coil to which an inverter-controlled auxiliary coil current is supplied so that the phase is shifted by 1/2π with respect to the main coil current, the electric motor reaches a rotational speed corresponding to the frequency of the main coil current, when accelerating the electric motor, the frequency of the auxiliary coil current is made higher than the frequency of the main coil current to drive the auxiliary coil in one phase, On the other hand, when decelerating the electric motor, the frequency of the auxiliary coil current is lower than the frequency of the main coil current, and the auxiliary coil is driven in one phase. .

[Operation of the invention] Since the present invention is configured as described above, when starting the electric motor, the phase is 1/1 with respect to the main coil and the main coil current.
A high starting torque is obtained by driving the auxiliary coil in two phases, which are supplied with auxiliary coil current controlled by an inverter so as to be shifted by 2π.

Then, when the electric motor reaches the required rotation speed, the electric motor is driven in one phase only by the auxiliary coil with a low occupation rate,
The power consumption of the electric motor is reduced. During one-phase driving by the auxiliary coil, the electric motor can be driven at variable speeds with relatively low torque by controlling the inverter to increase or decrease the frequency of the auxiliary coil current.

[Example code] Hereinafter, the present invention will be explained according to examples.

FIG. 1 shows an example of a circuit embodying the drive method of a single-phase induction electric motor according to the present invention, and FIG. 2 shows an inverter circuit.
In the figure, the main coil 3 of the electric motor 1 is connected to an AC power source A.
C is connected. A switching member 5 such as a relay or a triac is connected in series to the main coil 3. Further, a current detection coil 7 is attached to the main coil 3, and the detection current from the current detection coil 7 is used as a synchronization detection signal for shifting the phase of the frequency of the auxiliary fill current by 1/2π with respect to the main coil current. It is used as a disconnection signal for interrupting the supply of auxiliary coil current by the inverter circuit 9 when the electric motor 1 reaches a rotational speed corresponding to the frequency fO. An inverter circuit 9 is connected in parallel to the main coil 3, and an auxiliary coil 11 is connected to the output side of the inverter circuit 9. Further, the opening/closing member 5 is connected to the output side of the inverter circuit 9, and the opening/closing member 5 is controlled to open or close by commands from the inverter circuit 9. The auxiliary coil 11 is provided with a current detection coil 8, and the current detection coil 8 changes the rotation speed of the electric motor 1 to a variable speed, so that the rotation of the electric motor 1 corresponds to the auxiliary coil current supplied to the auxiliary coil 11. The speed detection signal is input to the inverter circuit 9 as a speed detection signal for detecting the number.

Four power transistors Tr1 to 7r4 and the auxiliary coil 11 are bridge-connected to the rectifier circuit 13 of the inverter circuit 9. The rectifier circuit 13 rectifies the supplied alternating current into a direct current and supplies it between the emitters and collectors of the power transistors Tr1 to Tr4. In addition, 15 in the figure is a regenerative capacitor.

A synchronization circuit 17 is connected to the current detection coil 7, and the synchronization circuit 17 forms a synchronization signal whose phase is shifted by 1/2π with respect to the main coil current supplied to the main coil 3.

A waveform shaping circuit 19 is connected to the synchronization circuit 17, and the waveform shaping circuit 19 shapes the input synchronization signal into a rectangular wave. A ROM 23 and a RAM 25 are connected to the central processing unit (hereinafter referred to as CPU) 21, respectively. The RO
M23 has a program memory area 27 and a frequency data area 29. The program memory area 27 stores program data for inverter control and PWM control of the electric motor 1 at a required frequency. Further, the frequency data area 29 includes the electric motor 1
Frequency data of the auxiliary coil current corresponding to the rotational speed of the motor is stored.

The RAM 25 has a timer area 31, and the timer area 31 measures the frequency of the auxiliary coil current based on its period.

A pulse generation circuit 33 is connected to the CPU 21.

The pulse generation circuit 33 generates a pulse signal corresponding to a required pulse width for PWM control of the auxiliary coil current according to the frequency of the auxiliary coil current. The pulse width of this pulse signal is PWM controlled so that the composite waveform of the effective value current of the auxiliary coil current approximates the waveform of the main coil current. The pulse generating circuit 33 includes power transistors Tr1 to Tr1 to T.
The drive circuits 35a to 35d of r4 are connected. Each drive circuit 35a to 35d is composed of a light emitting element and a light receiving element (none of which are shown), and emits light from the light emitting element according to the pulse width of the input pulse signal, and receives light according to the light emission from the light emitting element. A base current output from the element is applied to the base of each power transistor Tr1 to Tr4. As a result, each power transistor Tr1-Tr4, Tr2-T
r3 turns ON-OFF sequentially according to the pulse width of the pulse signal
controlled. Note that, for example, when outputting the positive component of the auxiliary coil current, the power transistors Tr1 and Tr4 are used, and when outputting the negative component, the power transistor Tr2 is used.
-Tr3 is ON-OFF controlled by the pulse signal PW'MlI111.

A rectifier circuit 37 is connected to the current detection coil 7, and the rectifier circuit 37 rectifies a detection current corresponding to the main coil current into a direct current. An A/D converter circuit 39 is connected to the rectifier circuit 37, and the A/D converter circuit 39 converts the DC current corresponding to the main coil current into a digital signal and converts it into a digital signal.
Output to U21. As a result, when the electric motor 1 reaches a rotational speed corresponding to the required frequency fO, the CPU 21 cuts off the supply of auxiliary current from the inverter circuit 9 based on the disconnection signal from the current detection coil 7, and The motor 1 is driven in one phase only by the main coil 3. Also,
A rectifier circuit 41 is connected to the current detection coil 8, and the rectifier circuit 41 rectifies the detected current detected according to the auxiliary coil current into a direct current. The rectifier circuit 41 has an A/
A D converter circuit 43 is connected, and the A/D converter circuit 43 converts a DC current corresponding to the auxiliary coil current into a digital signal and outputs the digital signal to the CPU 21 . This allows electric motor 1 to be driven at variable speed! I! When the electric motor 1 rotates, the rotation speed of the electric motor 1 is detected.

Next, a driving method of the single-phase induction electric motor configured as described above will be explained with reference to FIGS. 3 and 4.

In FIG. 3 showing the waveforms of the main coil current and auxiliary coil current at startup and FIG. 4 showing the driving state, when the power switch 4 is turned on, alternating current is supplied to the main coil 3 and the inverter circuit 9. . At this time, the alternating current supplied to the inverter circuit 9 is rectified into a direct current by the rectifier circuit 13, and is then rectified by the power transistors Tr1 to Tr.
Based on 4-2, the phase is shifted by 1/2π with respect to the main coil current supplied to the main coil 3 by the synchronization circuit 17, and in synchronization with the rectangular wave whose waveform is shaped by the waveform shaping circuit 19. frequency fO and phase is 1/2π
The pulse generation circuit 33 is driven in the shifted state. As a result, the pulse generation circuit 33 has a phase of 1 with respect to the main coil current.
A pulse signal for PWM control of the auxiliary coil current is output to the drive circuits 358 to 35d at timings shifted by /2π to power transistors Tr1, Tr4, Tr2, and 7.
r3 is sequentially ON-OFF controlled. As a result, an auxiliary coil current whose phase is shifted by 1/2π from the main coil current is supplied to the auxiliary coil 11 to form a rotating magnetic field, and the electric motor 1
Activate.

When the electric motor 1 reaches a rotational speed corresponding to the frequency fO of the main coil current, the CPU 21 controls the current detection coil 7
The supply of auxiliary coil current by the inverter circuit 9 is cut off based on the detected current from the inverter circuit 9, and the electric motor 1 is driven to rotate only by the main coil 3. This avoids inverter noise that occurs when the rotational speed of the electric motor 1 and the auxiliary coil current generated by the inverter circuit 9 match.

When it is desired to accelerate the electric motor 1 to a rotation speed corresponding to the frequency fO or higher, the CPU 21 operates the opening/closing member 5 to cut off the supply of main coil current, and at the same time
1, the pulse generating circuit 3 has a frequency f1 (fl > fo) higher than the frequency fO, and supplies a PWM-controlled auxiliary coil current.
Drive 3.

As a result, the frequency of the auxiliary coil current is increased while the rotational speed of the electric motor 1 is detected based on the speed detection signal from the current detection coil 8, and the electric motor 1 is acceleratedly driven.

It should be noted that when the rotation speed of the electric motor 1 drops below the rotation speed corresponding to the required frequency f3 due to load fluctuation during acceleration driving of the electric motor 1, the CPU 21 detects the speed of the main coil based on the speed detection signal from the current detection coil 8. 3 and auxiliary coil 1
1 is driven in two phases to return the electric motor 1 to the required rotational speed corresponding to the frequency f1.

On the other hand, when the electric motor 1 is to be decelerated, the CPU 21 operates a pulse generating circuit to supply the auxiliary coil 11 with a PWM-controlled auxiliary coil current having a frequency f2 (fO>f2) lower than the frequency fO. 33 is driven. As a result, the frequency of the auxiliary coil current is lowered while detecting the rotation speed of the electric motor 1 based on the speed detection signal from the current detection coil 8.
to slow down. Incidentally, when the rotation speed of the electric motor 1 drops below the required rotation speed during deceleration driving of the electric motor 1, the CPU 21 controls the main coil 3 and the auxiliary coils 11 and 2 based on the speed detection signal from the current detection coil 8. The electric motor 1 is returned to the rotational speed corresponding to the required frequency f2 by phase driving.

As described above, in this embodiment, until the rotational speed of the electric motor 1 reaches the rotational speed corresponding to the frequency fo, two-phase driving is performed by the main coil 3 and the auxiliary coil 11 to generate a high driving torque of 1q. When the rotation of the electric motor 1 reaches a rotation speed corresponding to the frequency fO and the electric motor 1 is to be driven at a rotation speed corresponding to the frequency fO of the main coil current, the supply of auxiliary coil current by the inverter circuit 9 is stopped. Cut off and main coil 3
The electric motor 1 is driven only by the electric motor 1 to prevent inverter noise. Furthermore, when driving the electric motor 1 at variable speed, it is possible to control the electric motor 1 at variable speed by driving only the auxiliary coil in one phase and varying the frequency of the auxiliary coil current to frequency f1 or frequency f2. .

In the above explanation, a synchronization signal whose phase is shifted by 1/2π is formed by the synchronization circuit 17 based on the detected current from the current detection coil 7 corresponding to the frequency of the main coil current, and the auxiliary coil current is controlled by the inverter using the synchronization signal. However,
Without setting up a synchronous circuit, the CPU 21 controls the auxiliary coil current so that the phase thereof is 1/1/1 with respect to the frequency of the main coil current.
It may be controlled to shift by 2π.

Furthermore, in the above explanation, the auxiliary coil current is subjected to PWM control as shown in FIG. 3, but as shown in FIG. 5, the auxiliary coil current is PWM controlled to generate an alternating current that approximates the main coil current. It may be formed.

In the above explanation, the current detection coil 8 is provided in the auxiliary coil 11 to detect the rotation speed of the electric motor 1, but the rotation speed detection means may be an alternating current generator (tacho generator), an encoder, etc. good.

[Effects of the Invention] Therefore, the present invention is capable of starting with high torque, and after the required rotational speed has been reached, it is possible to start with low torque by using an auxiliary coil with a low occupation rate. It is possible to provide a drive system for a single-phase induction electric motor that can be driven at variable speeds.

[Brief explanation of the drawing]

Figure 1 is a circuit diagram showing an example of a circuit embodying the drive method of a single-phase induction electric motor, Figure 2 is a circuit diagram showing an inverter drive circuit, and Figures 3 and 4 are single-phase induction by a drive device. FIG. 5 is an explanatory diagram showing the driving action of the type electric motor, and FIG. 5 is an explanatory diagram showing a modified embodiment of the present invention. In the figure, 1 is an electric motor, 3 is a main coil, 9 is an inverter circuit, and 11 is an auxiliary coil.

Claims (1)

[Claims] (1) In a single-phase induction electric motor that rotates as the main coil and auxiliary coil are driven, when the electric motor is started, the main coil to which the main coil current is supplied is out of phase with the main coil current. After obtaining starting torque by driving the auxiliary coil in two phases with the auxiliary coil to which the auxiliary coil current is supplied with an inverter-controlled auxiliary coil current so as to be shifted by 1/2π, the electric motor reaches a rotation speed corresponding to the frequency of the main coil current. When accelerating the electric motor, the frequency of the auxiliary coil current is higher than the frequency of the main coil current to drive the auxiliary coil in one phase, and conversely, when driving the electric motor at deceleration, the auxiliary coil current is set higher than the frequency of the main coil current. A drive system for a single-phase induction electric motor, characterized in that the frequency of the current is lower than the frequency of the main coil current to drive the auxiliary coil in one phase.