Three-phase load power regulator. Encyclopedia of radio electronics and electrical engineering

Encyclopedia of radio electronics and electrical engineering / Regulators of current, voltage, power

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In domestic conditions, a three-phase power regulator is often needed for an active-reactive load. Similar constructions have been repeatedly described on the pages of magazines [1].

Readers are offered one more solution to the problem. This construction is a "synthesis" of two constructions described in [2, 3]. The power regulator allows you to control a three-phase load both individually for each phase, and simultaneously on all phases.

Initially, the device was developed to test phase control relays of the RNPP-311, EL-11, -12, -13, Ganz KK types during the commissioning and testing of automatic transfer transfer (ATS) circuits during commissioning in electrical engineering, allowing you to simulate voltage reduction modes, voltage asymmetry , phase loss without turning off the phase control relay and without using LATR.

A distinctive feature of the design is the absence of transistors, complete galvanic isolation of the control circuit and power circuits. The device is easy to set up, assembled using modern inexpensive parts, reliable in operation.

The electrical circuit diagram is shown in the figure.

(click to enlarge)

The channels for generating a clock pulse at the moment of voltage zero crossing in phases A and B are identical and consist of optocouplers U1, U2, logic elements DD1.1, DD1.2 [2]. At the moment the voltage passes through zero, short positive pulses are formed at the outputs 3, 6, 8 of DD1. On the elements VD6, C5, R14, VD7, C6, R15, VD8, C7, R16, sawtooth voltage generators (SPG) are assembled [3]. From the outputs of the GPN, the sawtooth voltage is supplied to the inverse inputs of the voltage comparators DA2.1, DA2.2, DA2.3. The direct inputs of the comparators receive the control voltage from the resistors R29, R30, R31 in phases A, B, C, R32 - common. At the outputs of the comparators, PWM sequences are formed phase by phase, which are fed to the inputs of the optocouplers U3, U4, U5 included in the control circuits of the triacs VS1, VS2, VS3. Thus, the loads are controlled in phases A, B, C. The device is powered from phase C (conditionally).

The power supply is assembled according to the classical scheme, consisting of a step-down transformer Tr1, a VD3 rectifier, and a DA1 stabilizer. The circuit for generating a sync pulse at the moment the voltage passes through zero is assembled on the elements R9, R10, VD4, DD1.3. LEDs VD9, VD10, VD11 serve to indicate the status of the outputs (in the author's version they correspond to the color marking of phases A yellow, B - green, C - red).

Details. The device uses resistors of the MLT type, variable resistors R29, R30, R31, R32 in the author's version of SP3-23a. Capacitors are small-sized import production. Capacitors C8, C9, C10 with a minimum TKE type K5319. Diode bridges VD1-VD3 type RB157 (1000 V, 1,5 A), VD5 - 1N4007 (1,1 A). Diodes VD6-VD8 - KD552, KD503. Light-emitting diodes small-sized import production. Optocouplers U3-U5 - MOS3021, MOS3023. Chips DD1, DD2 type K555TL2 can be replaced by 74LS14, KREN5B7805. Triacs VS1-VS3, depending on the purpose and load power, can be VT-136-800, VT-138-800, VT-139-800, for "savings" they can be with insulated housings installed on one radiator (dimensions depend on power ) with a PC cooler. Transformer Tr1 for voltage 9 V and current 200 mA.

The adjustment of the circuit begins after checking the correctness of the installation when switched on to one phase. To do this, temporarily turn off the power circuits of the triacs A, B, C (it is possible by turning off the fuses .2, .3, .4). Conclusions A, B, C are combined at the input, they supply a voltage of 220 V, observing the polarity L, N (phase zero). They check the operation of the power supply of the device, an oscilloscope (preferably a two-beam one) checks for the presence of clock pulses at pins 3, 6, 8 DD1.1, DD1.2, DD1.3.

The pulses on all channels must be of the same duration. Given the spread of the parameters and values ​​of the elements, it may be necessary to select within a small range the resistance value of the resistors R1, R2, R7, R8, R9. Then check the presence of sawtooth voltage at the inputs of comparators DA2.1, DA2.2, DA2.3 (terminals 2, 6, 9 DA2). Sawtooth voltages at the inputs of the comparators must have the same amplitude and slope, it may be necessary to select the resistance value of the resistors R14, R15, R16.

Next, they check the change in the PWM sequence at outputs 3, 6, 8 DD2.1, DD2.2, DD2.3 when regulated by resistors R29, R30, R31, R32. If necessary, the adjustment range is "stacked" by connecting in series with the extreme terminals of the resistors R29, R30, R31, R32 fixed resistors, the value of which is best selected by means of a resistance bridge or tuning resistors (not shown in the diagram). At the maximum opening (at outputs 3, 6, 8 DD2.1, DD2.2, DD2.3 log "0"), check the current of optocouplers U3-U5 (15 mA in the order of listing types), if necessary, selecting the resistance of the resistors R5, R20, R21. By connecting the triacs, they check the regulation on the load (incandescent lamp). In rare cases, it may be necessary to select a triac. Having restored the circuit, they check its performance on a three-phase load (three incandescent lamps).

Attention! The device works at a voltage of 380 V! When working with the device, observe the safety regulations!

References:

1. Tushnov V.E. Three-phase load management//Elektrik. - 2001. - No. 6.
2. Tatarenko A.A. Phase indicator on the IC//Radioamator. - 2003. - No. 4.
3. Tatarenko A.A. A pill for TDE 101U2, or seriously about current regulators of welding transformers / / Elektrik. - 2003. - No. 2.

Author: A.A. Tatarenko

See other articles Section Regulators of current, voltage, power.

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