JPS5838079B2 - Hysteresis motor operation control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an operation control device for a hysteresis motor.

The operating characteristics of a hysteresis motor, which is a type of synchronous motor, are as shown in FIG.

In other words, the torque T generated by the motor even when the motor rotor is slipping relative to the synchronous speed (<S-+O)
is approximately constant, and during synchronous operation, operation continues in a state where the torque TL required by the load and the torque TN generated by the motor are balanced.

The current (2) also has a nearly constant value regardless of the slip S, and furthermore, the current value does not change during synchronous operation.

Under the condition that the power supply frequency fN is constant, the relationship between the input terminal voltage ■ and the output torque T, and the input terminal voltage ■ and the input current ■ is approximately T2k1・■2,■ in the practical range, with k1 and k2 as constants. It is 2k2・■.

Therefore, if the voltage V is increased, the escape torque TM of the motor increases and the motor becomes resistant to overload, but on the other hand, the reactive current increases, the copper loss and iron loss of the motor stator increase, and the efficiency decreases.

Furthermore, if a hysteresis motor with a large escape torque TM is used under a load condition of a low output torque TL, the second
As shown in the figure, both the efficiency and power factor decrease, the loss of the motor increases and the amount of heat generated increases, and the required capacity of the power source to drive the motor increases as the power factor decreases.

The operating state in which both the power factor and efficiency are the highest in the synchronous operation range is when the load torque TL is equal to the escape torque TM of the motor.

However, in general, when operating a hysteresis motor, the escape torque TM of the motor is not set equal to the load torque TL.

This is because if the load torque becomes larger than the planned value or if there are variations in the torque characteristics of the motor, the required load torque TL becomes larger than the escape torque TM and the step-out occurs. This is because, as shown in Fig. 3, the operation continues in a balanced state with slip SM.

In this state, a corresponding loss constantly occurs in the motor rotor, resulting in a decrease in efficiency and problems with the heat resistance of the rotor, which is not desirable.

Therefore, conventionally, as shown in FIG. 1, the motor terminal voltage (2) is set so that TL<TM, taking into consideration motor overload, variation in characteristics, etc.

However, in this case, as explained in Figure 2, TL-TM
It is undeniable that efficiency and power factor decrease with respect to this point.

An object of the present invention is to provide an operation control device for a hysteresis motor that can improve the efficiency and power factor of the motor as much as possible without interfering with the operation.

In order to achieve this object, the present invention provides an operation of a hysteresis motor which is equipped with a power supply device for driving a motor and whose output voltage can be adjusted, and which controls the output voltage of the power supply device according to the slippage of the driven hysteresis motor. A control device is constructed, and the embodiment shown in the drawings will be described in detail below.

FIG. 4 shows a circuit configuration of an embodiment of the operation control device according to the present invention.

The driven hysteresis motor 10 is driven by a variable frequency/variable voltage power supply 13 that includes a controllable forward converter 11 and an inverse converter 12 .

A pulse transmitter 14 is connected to the rotor shaft of the motor 10, and has a repetition frequency f2 proportional to the rotational speed of the motor 10.
An output pulse having a value of 0 is input from the pulse oscillator 14 to the frequency comparator circuit 15.

The frequency of the output voltage of the forward converter 12, that is, the input voltage V of the motor 10, is determined by the set frequency f1 of the oscillator 16.

This frequency control by the oscillator 16 is performed by controlling the firing phase of each controllable electric valve of the inverter 12 via a phase control circuit 17.

The output frequency f2 of the pulse generator 14 is the same as that of the motor 10.
is selected to be equal to the output frequency f1 of oscillator 16 when rotating at synchronous speed, ie zero slip.

The rotary transmitter 14 only needs to be able to detect the rotational speed of the motor 10, and instead of this, a rotary generator or back electromotive force detection may be used.

The frequency comparator circuit 15 compares both input frequencies f1 and f2 and outputs a voltage Vf corresponding to the difference, and its characteristics are S2 f1-f2-0 as shown in Figure 5a.
In this case, a negative constant value -■1 is output as the output voltage Vf, and when S=f1-f2>0, a positive constant value +■2
1.As shown in figure b, when S=f1-f2=0, the output voltage V
Output a negative constant value 1■1 as f, S=f, -f2>
When the voltage is 0, a voltage proportional to the value of f1-f2 may be output.

In any case, the frequency f1 corresponds to the frequency of the input power supply voltage of the motor 10, and the frequency f2 corresponds to the actual rotational speed of the motor 10, so the difference between the two frequencies f1-f2 corresponds to the slip S of the motor 10. It turns out.

Such a frequency comparison circuit can be realized by, for example, a combination of a reversible counter and an operational amplifier, a digital subtraction circuit and an operational amplifier, a frequency/voltage converter and an analog level comparison circuit, or the like.

The output voltage Vf of the frequency comparison circuit 15 is input to the integration circuit 18 and integrated, and the integrated output Vo is used to control the voltage control circuit 1.
9 to control the output voltage of the forward converter 11 and therefore the output voltage of the power supply device 13.

This output voltage is kept as low as possible without causing slippage in the motor 10.

Frequency comparison circuit 15 during operation of hysteresis motor 10
When a relationship of f1-f2>0 occurs between the two frequencies of human power f1 and f2, that is, when slippage occurs in the motor 10, the frequency comparison circuit 15 outputs an output Vf with a value corresponding to the frequency difference or slippage, The output voltage of forward converter 11 is increased via integration circuit 18 and voltage control circuit 19.

As a result, the input voltage (■) of the motor 10 is increased,
Escape torque TM increases.

Therefore, the escape torque TM exceeds the load torque TL and is pulled into synchronization again.

In other words, the frequency difference fl '2 is zero, that is, the motor 10
When is in a synchronous operation state, the frequency comparator circuit 15 outputs a negative voltage -1 as the output voltage Vf, and therefore the output voltage o of the integrating circuit 18 gradually drops.

Therefore, the output voltage of the forward converter 11 and the inverse converter 12, that is, the output voltage of the power supply 13, decreases, and the motor 10
The escape torque TM decreases.

Through the above-mentioned two operations of torque increase and decrease, the output voltage ■ is controlled so that the escape torque TM becomes the load torque TL on a steady basis, and as a result, the power factor or efficiency is at its maximum at any load torque TL. Continue driving.

The above operation is expected to have similar effects during accelerated driving.

In the embodiment shown in FIG. 4, the integration circuit 18 is connected to the voltage reference circuit 2.
An embodiment in which 0 is replaced by an adder 21 is shown in FIG.

The voltage reference circuit 20 inputs the reference voltage Vs regarding the output voltage ■ into the adder 21.

The output voltage Vf of the frequency comparison circuit 15 is also input to the adder 21, where an addition operation of both inputs is performed, and the operation result VS+Vf is input to the voltage control circuit 19.

The device shown in FIG. 6 basically operates in the same way as the device shown in FIG.

However, the device shown in FIG. 4, which includes the integrating circuit 18, is not affected by pulse-like circuit state changes because the integrating circuit 18 absorbs them, but on the other hand, there is a slight delay in operation even with normal changes.

On the other hand, the device shown in FIG. 6 has the characteristic that, while there is no delay in operation in the control system, it also responds to pulse-like state changes.

These two characteristics may be used individually or in combination depending on the circumstances.

FIG. 7 shows an example of application of the present invention to a case where one power supply device 13 drives a large number of hysteresis motors 101, 102, . . . , 10N.

Pulse transmitter 141, 142,... for each motor
14N, and frequencies f21 and f2 corresponding to the rotational speed of each motor detected by these pulse transmitters.
2, .

The comparison circuit 15 calculates the difference between the frequency f1 and the frequency f1 from the oscillator 16, and if any motor is slipping, an operation is performed to increase the output voltage (2) of the power supply device 14.

This allows all motors to continue operating in a synchronized state.

In the device shown in Fig. 7, if there is little variation in the load of each motor, a representative pulse transmitter is attached to only one of the many motors, and the speed detection signal is used to connect a common power source to all the motors. The output voltage of the device 13 may also be controlled.

This configuration has the advantage of reducing system cost because the number of pulse generators is reduced.

As described above, according to the present invention, it is possible to always obtain the best efficiency and power factor for any load torque, so it is possible to reduce power consumption, reduce heat generation, and improve the cooling configuration. It is possible to achieve simplification and reduction in the required capacity of the drive power source.

1. According to the present invention, the motor terminal voltage is automatically adjusted so that the optimum required acceleration torque determined by the moment of inertia of the load and the acceleration time can be obtained even if the motor fails not only during constant speed operation but also during accelerated operation. Therefore, it can be highly effective even in applications where operation and stopping are frequently repeated.

[Brief explanation of the drawing]

1, 2 and 3 are diagrams for explaining the characteristics of a hysteresis motor, FIG. 4 is a block diagram showing an embodiment of the device of the present invention, and FIGS. 5 a and 5 are diagrams, respectively. FIG. 4 is a diagram showing an example of the characteristics of the frequency comparison circuit; FIG. 6 is a block diagram showing another embodiment of the device of the present invention;
FIG. 7 is a block diagram showing a configuration example when the device shown in FIG. 4 is applied to drive a large number of motors. 10... Hysteresis motor, 11... Forward converter,
12... Inverse converter, 13... Variable frequency/variable voltage power supply device, 14... Pulse oscillator, 15... Frequency comparison circuit, 16... Oscillator, 17... Phase control circuit, 18... Integrating circuit, 19... Voltage control circuit, 20
... Voltage reference circuit, 21... Adder.

Claims (1)

[Claims] 1 A variable voltage power supply device for driving a driven hysteresis motor, a voltage control device for controlling the output voltage of the power supply device, and a slip detection device for detecting slippage of the hysteresis motor, an operation control device for a hysteresis motor configured to control an output voltage of the power supply device via the voltage control device in accordance with a detected slip of the hysteresis motor;