JPS59139890A - Input controlling method for ac motor and circuit device therefor - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an input control method and an electric circuit arrangement for an AC motor in which the motor current is supplied via a controlled output circuit.

Electric motor drives are designed to maximum requirements in all cases. The result of this is that during normal operation the electric motor drive is activated only during part-load operation. At that time, the electrical efficiency decreased and is now 0.
．． It sinks below 2.

The relatively large phase angle between the voltage applied to the motor and the motor current therefore also increases the reactive current portion, which increases the power losses which require additional active power to be produced.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide an input control method and an input control electric circuit arrangement for an AC motor, in which input savings are achieved when the motor is operated under partial load.

This problem is solved according to the invention in a method according to the preamble, in which the torque/speed characteristic curve of the motor is adjusted to the development of the motor current required for the rated speed, which is to be kept constant. It is solved by

Therefore, an output circuit exists for each peak value of the one-chord motor AC voltage applied to the motor.
The output circuit can be shut off at time intervals whose length is adjusted depending on the control current for the output circuit.

In order to solve this problem, according to the invention, a circuit arrangement as mentioned at the outset is provided, in which a pulse generator connected to the motor current circuit generates pulses to reduce the zero-crossing of the one-chord motor alternating current voltage applied to the motor. (Nulldurchg; ngen), respectively shifted in time in proportion to the motor current, and in order for the operational amplifier to receive and accept this pulse, a measuring signal proportional to the control current for the output circuit is sent to the pulse generator. The receiver is connected to the measuring circuit for inputting, and by means of a potentiometer connected to the operational amplifier, the setpoint value for the time offset of the pulses with respect to the zero crossing of the motor alternating voltage applied to the motor can be adjusted with the operational amplifier. , the output of the operational amplifier and the input of the amplifier are coupled, the amplifier receiving the sawtooth voltage of the sawtooth voltage generator at another input;
The frequency of the saw blade voltage is proportional to the frequency of the motor AC voltage,
Then, an amplifier output signal is generated at the output of this amplifier until the output signal of the operational amplifier and the saw blade voltage exceed a darkness value which is adjusted according to the rated output of the motor, and the output of the amplifier is one of the gates (Gatter). The second input of the gate is connected to the input and receives a square pulse with a period of each negative and positive half wave of the motor alternating current voltage, and the output of the gate simultaneously receives one of these square waves and the amplifier output signal. The extinction pulse (LZ
schipuls);

In this way, it is achieved that the motor is supplied with as much current as is required to maintain the exactly required rotational moment, in particular the squirrel cage rotor of the induction transmission. The adaptation of the input is continuous and is constantly changed due to the changing load on the motor. Savings of up to 40% can thus be achieved. Furthermore, the phase shift between motor voltage and motor current is improved and kept constant. This makes additional reactive current compensation unnecessary today.

The invention can be used in all areas of electric motor drive technology when the motor is operated partially or completely in part-load operation. Completely uncomplicated preparation (
(Nachr; stung) existing devices are possible. Further increases the lifespan of compressor motors and fl(lu) machines.

6- The present invention will be explained with reference to the drawings.

The embodiment of the power control device shown in the block diagram in FIG. 1 supplies the motor M with as much current as is necessary to maintain exactly the torque required for the rated speed to be maintained constant. that is achieved. The block diagram shows a pulse generator 1 which generates a pulse train (see Figure 2B) and which generates a stop-string motor alternating current voltage (
The time offset tα of the pulse train relative to the respective zero crossing point of FIG. 2A) is proportional to the motor current. This pulse train is supplied to an operational amplifier 2. A potentiometer P1 is connected to this operational amplifier 2, which is capable of adjusting a setpoint value in the form of setpoint voltage UsO (FIG. 2D) due to the time offset of the pulses with respect to the zero crossing point of the motor alternating voltage.

At another input of the operational amplifier 2 there is also a trigger circuit 1i which triggers the output circuit 80 control electrode as a measuring circuit for the control current! i'; 6 supply circuits are connected.

The supply circuit 5 has a voltage value U, (
Figure 2C). Output signal Uo of operational amplifier 2
(FIG. 2E) is applied to the input of amplifier 4. Another input of the amplifier 4 is connected to a sawtooth voltage generator 3, which generates a sawtooth voltage UR (FIG. 2F). An amplifier output signal is generated at the output of the amplifier 4, for example in the form of a rectangular signal (Uv in FIG. 2G), and the operational amplifier 2
Threshold value So (Fig. 2E) at which the output signal and the sawtooth voltage UR (Fig. 2F) are adjusted according to the rated output of the motor.
and SR (Fig. 2F). amplifier 4
The output signal Uv (Fig. 2G) is sent to the input of the gate 13 and periodically applies a rectangular pulse UMW (Fig. 2H) to the second input of the gate with the period of each negative and positive half-wave of the motor AC voltage. accept. One of these rectangular pulses (U in FIG. 2H) and the amplifier output signal U are simultaneously applied to the output of the gate 13.
v (Fig. 2G) is present at both gate inputs, respectively.
UL (Figure 2.1).

This extinguishing pulse is offset with the aid of a capacitor, not shown in detail, which is charged and discharged with the cycle of the motor alternating voltage, such that there is a time interval in which the motor alternating voltage passes its peak value. For this point in time, the control current for the control electrodes of the output circuit 8 is switched off in the trigger circuit 6 and the voltage profile for the motor alternating voltage shown in FIG. 2L is thus adjusted. In this manner, the amplitude of the respective sinusoidal motor alternating voltage is reduced, thereby also reducing iron losses in the motor.

The formation of the trigger pulse for the + trigger of the output circuit 8 takes place in the amplifier 4 by means of adjustable regulators, for example potentiometers P2 and R3. When optimally matched, this is indicated, for example, by a photodiode.

However, it is also possible to carry out automatic optimization by means of the optimization circuit 7. This optimization circuit activated by the start key P4 has a supply circuit 5 proportional to the control current.
The measured value U (FIG. 2C) as well as the pulses of the pulse circuit 1 (FIG. 2B) are supplied. Optimization circuit 7 by switching to the terminal for automatic optimization of switch 9
is connected to amplifier 4. Adjustments are made automatically once every 10 hours of automatic operation.

In order to utilize the voltage UM applied to the motor M (FIG. 2A) as well as the load current rL, the diode bridge 10]] acts and a suitable signal is transmitted to the pulse circuit 1 via the conductors R1 and R2. available.

Furthermore, the voltage UM used to assist the diode bridge 10 is applied to the saw blade voltage generator 3 via the line R1.

The output circuit 12 further includes a holding resistor RV and a starting protection resistor R5.
is provided.

A pulse screen is formed in the 1-rigger circuit 6 which is applied to the control electrode of the output circuit 8 .

In special cases, a switchable thyristor with a finger structure of control electrode and cathode is useful as the output circuit 8. Such shutoff thyristors are available, for example, from the electronic industry.
J3,] 982, pages 15-18.

10- In this manner a coupled adaptation of the input of the electric motor, in particular of the induction electric motor, in the respective load state is achieved.

The rotational moment of the induction electric motor shown in Fig. 3/
In the curve diagram shown in FIG. 3 of the rotational speed characteristic curve,
The rotational speed N of the motor is shown on the horizontal axis, and the rotational moment M of the motor is shown on the vertical axis.

Usually the motor drive is designed to the maximum requirements, for example in a part-load drive, the setpoint rotational speed UN is achieved by the setpoint rotational moment) MICA. As can be seen from the curve in FIG. 3, the rated speed UN is also achieved by a reduction in the rated torque, for example the rated torque MNB belonging to the torque/rotational speed characteristic curve B. Experimenting with moving the rotational moment/speed characteristic curve to the prehistory shows that the overturn of the motor ([Imk i
ppen), that is, it is not guaranteed that the rated speed U+V is maintained by the torque achieved.

[Brief explanation of the drawing]

1 is a block diagram of an embodiment of the present invention, 2A to 2 are curve diagrams for explaining the driving of the circuit shown in FIG. 1, and 3 is a rotation moment 1-/rotation speed characteristic curve. FIG. 1... Pulse generator 2... Operational amplifier 3...
Sawtooth voltage generator 4...Amplifier 5...Measurement circuit
8...Output circuit 13...Gatebi 1

Claims (1)

[Claims] (11. A method for controlling an input of an AC motor supplied according to a motor current via a controlled output circuit,
An input control method for an AC motor, characterized in that the rotational moment/rotational speed characteristic curve of the motor is adjusted to generate only the motor current necessary for the rated speed to be kept constant. (2) characterized in that the output circuit is interrupted in time intervals whose duration is adjusted according to the control current for the output circuit present for each peak value of the sinusoidal motor alternating voltage applied to the motor; A method as claimed in claim 1. (3) A circuit arrangement for the control of the input of an alternating current motor, which is supplied according to the motor current via a controlled output circuit, in which a pulse generator (1) connected to the motor current circuit generates pulses. , the zero crossing of the sinusoidal motor AC voltage applied to the motor (M)
The control current for the output circuit (8) is sent to the pulse generator (1) in order for the operational amplifier (2) to receive and accept these pulses. The reception of a measuring signal proportional to the zero crossing of the motor alternating voltage applied to the motor (M) by a potentiometer (P) connected to the measuring circuit (5) and connected to the operational amplifier (2) a target value for the time offset of the pulses for is adjustable in an operational amplifier (2), the output of the operational amplifier (2) and the input of the amplifier (4) being coupled;
The amplifier receives at another input the sawtooth voltage of the sawtooth voltage generator (3), the frequency of the sawtooth voltage being proportional to the frequency of the motor alternating voltage, and the output of this amplifier (4) An amplifier output signal is generated until the output signal of the operational amplifier (2) and the saw blade voltage exceed the darkness value, which is adjusted according to the rated output of the motor, and the output of the amplifier (4) is connected to the gate (Gatter) (1).
3) is connected to one input of the gate, the second input of the gate receives a rectangular pulse with a period of each negative and positive half-wave of the motor alternating voltage, and the output of the gate simultaneously receives one of these square waves and the amplifier. An extinguishing pulse (L3sc
himpuls).