JPS6237091A - Drive system of single phase induction type electric motor - Google Patents

Abstract

PURPOSE:To obtain high starting torque while efficiently controlling speed by connecting an inverter to a main coil and supplying the currents of the main coil, whose phase is shifted by 1/2pi with regard to the currents of an auxiliary coil. CONSTITUTION:An AC power supply AC is connected to a main coil 3 for an electric motor 1 through an inverter drive circuit 5, and an auxiliary coil 9 with which a switching member 7 is connected in series is connected in parallel with the main coil 3. The inverter drive circuit 5 is controlled so that the currents of the main coil, phase thereof is shifted by 1/2pi with regard to the frequency of the currents of the auxiliary coil detected by a current detecting coil 10 flow on starting. When the motor reaches the number of revolution corresponding to power frequency, the main coil 3 is driven by one phase. The motor can be accelerated or decelerated by controlling frequency.

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, an auxiliary coil in which a current relay and a capacitor are connected in series is connected in parallel to a main coil connected to an AC power source, and when the electric motor is started, the main coil and main coil current are The starting torque is obtained by forming a rotating magnetic field by driving an auxiliary coil in two phases to which auxiliary coil currents whose phases are shifted by a capacitor are supplied. When the electric motor reaches a required number of revolutions, the current relay returns as the main coil current decreases, cutting off the auxiliary coil current and driving the motor in one phase using only the main coil. However, in the above drive method, since the impedance of the auxiliary coil changes as the electric motor rotates, it is difficult to maintain the phase shift due to the capacitor to 1/2π, which is ideal for forming a rotating magnetic field. Yes, high starting torque could not be obtained. This drawback is that the main coil current and the auxiliary coil current are each controlled by an inverter, and when starting the electric motor, the auxiliary coil current is supplied with a phase shift of 1/2π with respect to the main coil and the main coil current supplied to the main coil. The starting torque is obtained by two-phase drive using an auxiliary coil. When it is desired to vary the speed of the electric motor to a required rotational speed, the speed of the electric motor is controlled by varying the frequencies of the main coil current and the auxiliary coil current.

[Problems to be Solved by the Invention] However, the drive system for controlling the main coil and the auxiliary coil with an inverter requires that the main coil and the auxiliary coil be turned on and off.
In order to control the FF, a large number of power transistors and their driving circuits are required, and the cost of the driving device increases.

[Object of the Invention] In view of the above-mentioned conventional drawbacks, the object of the present invention is to provide a single-phase induction electric motor that can obtain high starting torque at startup with a small number of parts and efficiently drive the electric motor. The objective is to provide a driving method.

[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, which are connected in parallel to an AC power source. After obtaining the starting torque by forming a rotating magnetic field by driving the auxiliary coil and the main coil supplied with the inverter-controlled main coil current with a phase shift of 1/2π with respect to the auxiliary coil current in two phases, When the electric motor reaches a rotational speed corresponding to the frequency of the AC power source, the main coil is driven in one phase,
A drive system for a single-phase induction electric motor is constructed by increasing the frequency of the main coil current to accelerate the electric motor, and conversely decreasing the frequency of the main coil current to drive the electric motor at deceleration.

[Operation of the Invention] Since the present invention is configured as described above, when the electric motor is started, the main coil current is supplied to the main coil under inverter control so that the phase is shifted by 1/2π with respect to the auxiliary coil current. Therefore, it achieves a high drive torque that is ideal for driving a single-phase electric motor. When the electric motor reaches a required rotational speed, the electric motor is driven in one phase by a main coil, and the frequency of the main coil current supplied to the main coil is controlled by an inverter to drive the electric motor at a variable speed. I can do it. Therefore, compared to a drive method in which the main coil and the auxiliary coil are controlled by an inverter, this drive method can reduce the number of parts and reduce the cost of the device.

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

In FIG. 1 showing an example of a circuit embodying the drive method of a single-phase induction electric motor according to the present invention and FIG. 2 showing an inverter drive circuit, the main coil 3 of the electric motor 1 is connected to an alternating current power source AC, and an inverter An auxiliary coil 9 is connected in parallel to the main coil 3 via a drive circuit 5, and to which a switching member 7 such as a current relay or a triac is connected in series. The opening/closing member 7 operates to open when the main coil current supplied to the main coil 9 becomes less than a required current value, and cuts off the supply of the auxiliary coil current to the auxiliary coil 9. The main coil 3 is provided with a current detection coil 8, and the current detection coil 8 outputs a main coil current, and thus a detection current corresponding to the rotation speed of the electric motor 1. In addition, the auxiliary coil 9
A current detection coil 10 is provided, and the current detection coil 10 detects the frequency of the auxiliary coil current for driving the main coil 3 in synchronization with the auxiliary coil current when the electric motor 1 is started.

Four power transistors Tr1 to Tr4 and a main coil 3 are bridge-connected to the output side of the rectifier circuit 11 of the inverter drive circuit 5. Note that 13 in the figure is a regenerative capacitor. A synchronous circuit 15 is connected to the current detection coil 10, and the synchronous circuit 15 has a phase of 1 with respect to the frequency of the auxiliary coil current detected by the current detection coil 10.
A synchronization signal shifted by /2π is formed. A waveform shaping circuit 17 is connected to the synchronization circuit 15, and the waveform shaping circuit 17 shapes the input synchronization signal into a rectangular wave.

The central processing unit (hereinafter referred to as CPU) of the inverter drive circuit 5
) 19, tROM 21 and RAM 23 are connected. The ROM 21 has a program memory area 25 and a frequency data area 27, and the program memory area 25 stores program data for inverter control and PWM control of the main coil current supplied to the main coil 3, as described later. be done. The frequency data area 27
Frequency data corresponding to the rotational speed of the electric motor 1, and thus the current value from the current detection coil 8, is stored in .

Is there a tie in RAM23? The timer area 29 measures the frequency according to the period of the main coil current.

A pulse generation circuit 31 is connected to the CPIJ 19,
The pulse generating circuit 31 generates a pulse signal having a pulse width that is PWM-controlled in accordance with the frequency of the main coil current supplied to the main coil 3. The pulse width of this pulse generation circuit 31 is PWM controlled so that the main coil current controlled by the inverter approximates the current waveform of the AC power source AC. Drive circuits 33a to 33d are connected to the pulse generating circuit 31 in accordance with the respective power transistors Tri to Tr4. Each of the drive circuits 33a to 33d is composed of a light emitting element and a light receiving element (none of which are shown), and a base that is output from the light receiving element in response to light from the light emitting element emitted according to the pulse width of the pulse signal. The current flows through each power transistor 7r.
l ·Tr4 is applied to the bases of Tr2 and Tr3. As a result, power transistors Tr1-Tr4
, Tr2-Tr3 are ON-OFF controlled according to the pulse width of the pulse signal, whereby a main coil current having a desired frequency is supplied to the main coil 3. In addition, to form the positive component of the main coil current, power transistors Tr1 and Tr4 are turned on, and to form a negative component, power transistors Tr2 and Tr3 are turned on and off.
ff1I1111 Sarel.

A rectifier circuit 35 is connected to the current detection coil 8, and the rectification circuit 35 rectifies the detected current from the current detection coil 8 into a direct current. The rectifier circuit 35 has an A/D
A converter circuit 37 is connected, and the A/D converter circuit 37 converts the input DC current into a corresponding digital signal and then outputs it to the CPtJ19.

Next, a method of driving a single-phase induction electric motor using the drive device having the above structure will be described with reference to FIGS. 3 and 4.

When the power switch 4 is turned on, the inverter drive circuit 5
An alternating current is supplied to the auxiliary coil 9 and the auxiliary coil 9. At this time,
The CPIJ 19 drives the pulse generation circuit 31 based on a synchronized square wave with a phase shift of 1/2π with respect to the frequency fO of the auxiliary coil current supplied to the auxiliary coil 9.
The phase is 1/2π at the frequency rO which is periodic to the auxiliary coil current.
The drive circuit 33a outputs a pulse signal that is shifted and PWM controlled.
~33d are output sequentially. As a result, the drive circuit 338~
33d, power transistors Tr1 to Tr4 and Tr2 to Tr3 are sequentially turned ON to OFFfililJt211 and the main coil 3 according to the pulse width by the input pulse signal.
As shown in FIG. 3, a main coil current whose phase is shifted by 1/2π with respect to the auxiliary coil current is supplied to the main coil current. As a result,
A rotating magnetic field is generated according to the two-phase drive of the main coil 3 and the auxiliary coil 9, and the electric motor 1 is started with high torque.

And the start of electric motor 1! After vI, when the electric motor 1 reaches a rotational speed corresponding to the frequency fO of the auxiliary coil current based on the detected current from the current detection coil 8, the opening/closing member 7 operates to open based on the main coil current, and the auxiliary coil Cut off the current. As a result, the electric motor 1 is driven by the main coil 3 in one phase.

Then, when you want to accelerate the electric motor 1, CP[J1
Reference numeral 9 performs inverter control on the main coil current using frequency data stored in the frequency data area 27 based on the detected current from the current detection coil 8, thereby increasing the frequency of the main coil current. As a result, the electric motor 1 is accelerated by one-phase drive by the main coil 3. Incidentally, when the rotational speed of the electric motor 1 drops to the required rotational speed f3 during acceleration driving of the electric motor 1, the CPLJ 19 operates the opening/closing member 7 to switch the electric motor 1 through the main coil 3 and the auxiliary coil 9. 2
The rotational speed of the electric motor 1 is returned to the required rotational speed by phase driving and acceleration driving.

On the other hand, when you want to drive the electric motor 1 at a reduced speed, the CPU 1
Reference numeral 9 controls the frequency of the main coil current using an inverter based on the detected current from the current detection coil 8 and the frequency data stored in the frequency data area 27, thereby lowering the frequency of the main coil current.

As a result, the electric motor 1 is decelerated by the one-phase drive of the main coil 3. Note that when the rotational speed of the electric motor 1 decreases to the required rotational speed f4 during deceleration driving of the electric motor 1, C
The PU 19 operates the opening/closing member 7 to drive the electric motor 1 in two phases using the main coil 3 and the auxiliary coil 9 to accelerate the electric motor 1 and return the rotational speed of the electric motor 1 to the required rotational speed.

In this way, in this embodiment, when starting the electric motor 1, the main coil current whose phase is shifted by 1/2π from the auxiliary coil current is supplied to the main coil 3, so that an ideal rotating magnetic field is formed to drive the electric motor. 1 can be started. When the electric motor 1 reaches a rotational speed corresponding to the frequency of the auxiliary coil current, it is driven by the main coil 3 in one phase. At this time, the electric motor 1 can be accelerated and driven by increasing the frequency of the main coil current supplied to the main coil 3. On the contrary, it is possible to drive the electric motor 1 at a reduced speed by lowering the frequency of the main coil current.

In the above explanation, a synchronization signal whose phase is shifted by 1/2π is formed by the synchronization circuit 15 based on the detected current from the current detection coil 1o corresponding to the frequency of the auxiliary coil current, and the main coil current is controlled by the inverter using the synchronization signal. However, without providing a synchronous circuit, the main coil current is controlled by the CPU so that the phase is 1/2π with respect to the frequency of the auxiliary coil current.
It may also be controlled to shift.

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

In the above explanation, the main coil 3 is provided with the current detection coil 8 in order to detect the rotation speed of the electric motor 1.
, encoder, etc.

[Effects of the Invention] Therefore, the present invention can provide a drive system for a single-phase induction electric motor that can obtain high starting torque at startup with a small number of parts and efficiently drive the electric motor. It is.

[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 illustrating the operation of the type electric motor drive system, 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, and 9 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, which are connected in parallel to an AC power source, when the electric motor is started, the phase of the auxiliary coil and the auxiliary coil current is 1. After obtaining a starting torque by forming a rotating magnetic field by driving the main coil in two phases to which the main coil current is supplied with an inverter-controlled main coil current shifted by /2π, the electric motor rotates according to the frequency of the AC power source. When the number is reached, the main coil is driven in one phase, the frequency of the main coil current is increased to accelerate the electric motor, and conversely, the frequency of the main coil current is lowered to drive the electric motor at deceleration. A drive system for a single-phase induction electric motor.