Torque drive. Scheme, description

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Torque drive. Encyclopedia of radio electronics and electrical engineering

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Encyclopedia of radio electronics and electrical engineering / Electric motors

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Torque electric drives make it possible to quite simply implement control systems for unwinding and winding devices, where the use of tension sensors is undesirable, for example, for film materials with a deposited layer, mechanical contact is impossible.

The proposed electrical circuit of the torque electric drive (see figure) ensures the operation of the DC motor for unwinding in a stalled mode and the regulation of the tension of the tape material within 1-10 kg.

The electric drive for winding provides linear speed control of the DC motor shaft for unwinding in a stalled mode and the regulation of the tension of the tape material within 1...10 kg.

The electric drive for winding provides linear regulation of the speed of rotation of the motor shaft from 0,6 to 700 rpm. Electric motors are used without gearboxes.

(click to enlarge)

The electric drive has an automatic speed limiter in the event of a break in the tape material. The function of the electric drive control system is to control the output parameter - the tension of the tape material. The single-circuit automatic tension control system is built on the principle of comparing the driving voltage taken from the setter Rp (proportional to the required tension) with the feedback voltage on the motor armature current M (proportional to the torque developed by the electric motor). The error signal affects the control system, rebuilding the controlled rectifier on the elements VS3, VS4, VD23 and VD24 in such a way that the desired voltage change occurs at the motor armature.

The current regulator (RT) is made on the operational amplifier DA1, connected according to the proportional-integral (PI) regulator circuit. Resistor R3 and capacitor C1 are elements that form the PI-law of regulation of the output parameter DA1. Capacitors C2 and C3 are filters for power supplies DA1. The setting voltage from the regulator Rp is supplied to the inverting input DA1 through the resistor R1, and here, through the resistor R2, the current feedback voltage from the sensor R29 is supplied. Through the resistor R4, the output voltage DA1 is fed to the input of the operational amplifier DA2, designed to invert the output voltage of the current regulator to DA1 and supply voltage to the phase shifter. A single inverter on an operational amplifier DA2 with a threshold element, a zener diode VD1 serves to limit the control voltage.

The divider on resistors R8 and R9 at the non-inverting input DA2 is designed to select the control voltage level, which is necessary when setting the control range of the controlled rectifier VS3, VS4, VD23 and VD24. The control voltage from the inverter (DA2) is fed to the input of the operational amplifier DA3 of the phase shifter (FU). The FU consists of a sawtooth voltage generator made on a VT1 transistor and a null organ on an DA3 operational amplifier. The principle of operation of the FU is based on the algebraic summation of the output voltages taken from the DA2 and the sawtooth voltage generator.

Transistor VT1 is switched by a pulsating voltage with a frequency of 100 Hz supplied from the diode bridge VD2 ... VD5, fed from winding II of transformer T1. The null organ on DA3 generates pulses according to voltage phase, duration and amplitude.

The voltage from the output of DA2 and transistor VT1 is fed to the input of the null body DA3. At the moment when the negative signal from the collector VT1 and the positive signal from the output DA2 are compared in amplitude, the polarity of the output voltage DA3 changes from negative to positive, the transistor VT2 opens and remains open until the end of the switching voltage period. In the emitter circuit VT2, the load is the LEDs of the thyristor optocouplers VS1 and VS2. The thyristors of the optocouplers VS1 and VS2 turn on, a positive voltage is applied to the control electrode of one of the thyristors of the controlled rectifier VS3 or VS4, depending on the polarity of the mains voltage. The controlled single-phase thyristor rectifier is made according to an asymmetric bridge circuit. To power the operational amplifiers with a stabilized voltage of ±15 V, a stabilizer with an operational amplifier DA4 is used, which makes it possible to achieve a high stabilization coefficient and a low output impedance.

The stabilizer provides an output voltage of ±15 V at a load current of 500 mA. Reliable start of the stabilizer when turned on is ensured by a positive feedback circuit from the collector VT3 to the non-inverting input DA4 through the resistor R20. Resistor R23 and capacitor C9 carry out frequency correction DA4.

Details: Operational amplifiers DA1...DA4 type K140UD7.

Resistor Rp type PPB-3A, PPB-15E can also be SCH2M, R27 - PPB-3A, PP3-43, resistor R29 is wire, the rest are MLT type.

Capacitors: C1, C6, C9 type K73-17, electrolytic capacitors C2 - C8 - K50-6x25 V.

Трансформатор Т1-ТА14-127/220-50.

Optocoupler thyristors VS1 and VS2 - AOU115D, AOU103V.

Thyristors VS3, VS4 - T10-50-8, T142-50-8.

Diodes VD23, VD24 - D10-50-8, D112-50-8.

Thyristors VS3 and VS4 - diodes VD23, VD24 are installed on coolers 0241, transistor VT3 - on a radiator 25 cm2, zener diodes VD7 and VD8 type D815E - on a radiator made of a U-shaped aluminum plate, area 6 cm2.

DC electric motors with a tachogenerator with a power of 1-4,7 kW. In cases where the tachogenerator has independent excitation, it is necessary to provide a rectifier.

Establishing an electric drive is reduced to setting the initial level of the control voltage using resistor R9, then using resistor R27, the speed limit of the electric motor is set. Regulate the speed of the motor with resistor R5.

Electric drives in winding and unwinding modes for tape materials have been in operation for a long time and have shown high reliability. They can be used for paper and other purposes.

Author: V.F. Yakovlev

See other articles Section Electric motors.

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