JPH06101953B2 - AC motor speed controller - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an AC electric motor whose speed is controlled using a thyristor.

[Conventional technology]

As shown in FIG. 6, a common bidirectional thyristor 23 is connected to an auxiliary winding 21 in which a main winding 20 and a capacitor 22 are connected in series, and an alternating current is controlled by on / off time ratio control or phase control. A method of controlling the voltage applied to the electric motor has been adopted.

The drawback is that the ON / OFF time ratio control has a high vibration level because it is ON / OFF control, and the phase control causes a significant distortion of the voltage waveform, resulting in large noise.

[Problems to be solved by the invention]

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above drawbacks and provide an AC electric motor with less noise and vibration.

[Means for solving problems]

In the present invention, in order to solve the above problems, the main winding of the AC motor is divided into two, and a bidirectional thyristor is connected in series to each of them as shown in FIG. AC thyristor connected in series, a speed setting unit for setting the rotation speed of the AC motor arbitrarily or stepwise, for example, high, medium or low speed, and an output signal of the speed setting unit And an ON / OFF time ratio control section for controlling the ON / OFF operation of the bidirectional thyristor in response to the output signal of the synchronization signal generation section synchronized with the power supply, and a speed detection section for detecting the rotation speed of the AC electric motor. Output signal from the speed setting unit and a speed control unit that detects an error in the rotation speed to instruct fine adjustment of the rotation speed, and an auxiliary winding side that receives the output signal from the speed control unit The interactive squirrel It was more configuration and phase controller for controlling on-off operation.

[Action]

According to the above configuration, when the target rotation speed is set by the operation knob or the like provided in the speed setting unit, the speed setting unit sends the output signal corresponding to the target rotation speed to the on / off time ratio control unit and synchronizes with the power supply. The on / off time ratio control unit controls the bidirectional thyristor 5 or 6 in accordance with the output signal of the speed setting unit so that the voltages applied to the main winding 1 and the main winding 2 do not become in the conduction stop state at the same time. It has a function of selecting a control signal to be supplied to the gate terminal.

On the other hand, the rotation speed detected by the speed detection unit is compared with the target rotation speed by the speed control unit to detect an error, and the bidirectional thyristor 7 is operated through the phase control unit according to the error. The rotation speed can be finely adjusted by the feedback control of.

〔Example〕

 Embodiments of the present invention will be described with reference to the accompanying drawings.

As shown in FIG. 1, the AC motor speed control apparatus according to the present invention divides the main winding of the AC motor into two main windings 1 and 2, and bidirectional thyristors 5 and 6 are connected in series to the main windings 1 and 2, respectively. , A capacitor 4 and a bidirectional thyristor 7 are connected in series to the auxiliary winding 3 to form a parallel circuit, terminals 8 and 9 are provided at both ends of the parallel circuit, and the AC commercial power source 10 is connected. It constitutes the electric circuit of the electric motor.

Next, the control circuit for ON / OFF controlling the bidirectional thyristors 5, 6 and 7 in the electric circuit will be described in detail. 11 generates a signal synchronized with the power supply voltage at the beginning of every cycle of the power supply. The synchronizing signal generator, 13 is a speed setting unit, and has a role of transmitting a signal corresponding to each setting such as high speed, medium speed, and low speed. An on / off time ratio control unit 12 receives a synchronization signal from the synchronization signal generation unit 11 and a signal corresponding to a target rotation speed from the speed setting unit 13 and applies the main winding 1 and the main winding 2. A control signal to be supplied to the gate terminals of the bidirectional thyristors 5 and 6 is selected so that the voltage does not become the conduction stop state at the same time during the operation other than the purpose of stopping the operation. Reference numeral 14 denotes a rotation speed detection unit of the AC motor, and the detection signal is sent to a speed control unit 15 to determine whether or not to finely adjust the rotation speed in proportion to the target rotation speed set by the speed setting unit 13. When the rotation speed is lower than the target rotation speed, the control signal is continuously sent to the phase control unit 16. Therefore, the phase control unit 16 receiving the control signal from the speed control unit 15 can drive the bidirectional thyristor 7 and apply a voltage to the auxiliary winding 3 to finely adjust the rotation speed. In this case, it is possible to control from the range of Tmax (N) -Tomax (N) to the range of Tmin (N) -Tomin (N) like the speed-torque characteristic curve shown in FIG.

Hereinafter, high speed / medium speed / low speed rotation will be described. The voltage waveform applied to the main windings 1 and 2 during high speed rotation is shown in FIG. In high-speed rotation, it is not necessary to control the on / off time ratio, and when the firing signal is supplied to each gate terminal of the bidirectional thyristors 1, 2 and 3 throughout the entire cycle, the main winding 1
Since the voltage shown in FIG. 2 is applied to and 2, the AC motor rotates at a high speed at a speed substantially synchronized with the power supply frequency.

Next, the low speed rotation according to the present invention will be described. The voltage waveform applied to the main windings 1 and 2 during low speed rotation is shown in FIG. Turns on when low speed rotation is set in the speed setting section.
A signal supplied to the gate terminals of the bidirectional thyristors 1 and 2 is alternately transmitted by the off-time ratio control unit for each cycle of the power supply voltage. Therefore, the current flowing through the main windings 1 and 2 is about one half of that at the high speed rotation, and the rotation speed is also reduced to about one half.

Next, an example of the medium speed rotation according to the present invention will be described.

The voltage waveforms applied to the main windings 1 and 2 during medium speed rotation are shown in FIG. When the medium speed rotation is set in the speed setting unit, a signal to be supplied to the gate terminals of the bidirectional thyristors 1 and 2 in the ON / OFF time ratio control unit is set to 1 cycle for every 3 cycles (plural cycles) of the power supply voltage. A conduction cycle having a stop period is selected, and when one of the conduction cycles is in a non-conduction state, the other is alternately transmitted so that it is always in a conduction state. Therefore, the current flowing through the main windings 1 and 2 is about 3/4 of that at the time of high-speed rotation, and the rotation speed is reduced to about 3/4.

As will be understood from the above description, the device according to the present invention can be applied to any induction motor such as a condenser run type or a condenser start type, and can drive a wide range of alternating current motors such as a synchronous motor at a low speed.

In the present invention, the one using the bidirectional thyristor has been described, but the present invention is not limited to this, and two unidirectional thyristors connected in anti-parallel may be used.

〔effect〕

By applying the device according to the present invention as compared with the conventional method in which the AC motor is intermittently operated by the on / off time ratio control or the phase control, the noise and vibration generated at the middle speed / low speed rotation can be improved to a low level, and the rotation speed can be improved. Since the feedback control can be performed, speed control can be performed quickly. Further, the present invention can be applied to various induction motors and synchronous motors, and thus has great industrial value.

[Brief description of drawings]

FIG. 1 is an electric circuit diagram showing an embodiment of a speed control device for an AC motor according to the present invention, and FIGS. 2 to 4 are voltages applied to a main winding 1 and a main winding 2 according to the embodiment. FIG. 5 is a diagram showing a waveform, FIG. 5 is a characteristic curve diagram showing the relationship between the rotational speed (N) and torque (T) according to the embodiment, and FIG. 6 is an electric circuit diagram showing a conventional example. In the figure, 1 and 2 are main windings, 3 are auxiliary windings, 4 are capacitors, 5, 6 and 7 are bidirectional thyristors, and 8 and 9
Is a terminal, 10 is an AC commercial power supply, 11 is a synchronizing signal generator, 12 is an on / off time ratio controller, 13 is a speed setting unit, 14 is a speed detector, 15 is a speed controller, and 16 is a phase controller. is there.

Claims (1)

[Claims] 1. An AC motor comprising a main winding divided into two, a bidirectional thyristor is connected in series to each of the main windings, and a capacitor and a bidirectional thyristor are connected in series to the auxiliary winding, and the AC motor. Both the main winding side receives the speed setting section for setting the rotation speed of the electric motor arbitrarily or stepwise, and the output signal of the speed setting section and the output signal of the synchronizing signal generating section synchronized with the power supply. A signal to be supplied to the gate terminal of the directional thyristor is alternately sent out every cycle of the power supply voltage at low speed rotation, and a conduction cycle having a stop period of one cycle is selected every plural cycles of power supply voltage at medium speed rotation, An ON / OFF time ratio control unit for controlling the ON / OFF operation of the bidirectional thyristor on the main winding side by alternately sending so that when one of them is in a non-conducting state, the other is always in a conducting state. ,Previous A speed control unit that receives an output signal of a speed detection unit that detects the rotation speed of the AC motor and an output signal of the speed setting unit, detects an error in the rotation speed, and instructs a fine adjustment of the rotation speed, and the speed control unit. And a phase control section for controlling the on / off operation of the bidirectional thyristor on the auxiliary winding side in response to the output signal from the AC winding.