Converter 1 phase network to 3-phase. Scheme, description

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ENCYCLOPEDIA OF RADIO ELECTRONICS AND ELECTRICAL ENGINEERING
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Master generator for converting a 1-phase network into a 3-phase one. Encyclopedia of radio electronics and electrical engineering

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Encyclopedia of radio electronics and electrical engineering / Power supply

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Moving around sites and forums, I often encounter the same problem: there are three-phase asynchronous motors, but there is no three-phase supply network. People contrive as best they can, the motors are connected to a single-phase network using a phase-shifting capacitor, as a result of a power loss of about 60% at best + difficult starting of the engine even under light loads. Of course, there are many different ways to connect three-phase motors in one phase, but they all have the same disadvantage of power loss.

The best way out of the situation seems to be the use of a 1-phase to 3 converter. A relatively simple circuit creates full power for three-phase asynchronous motors and allows them to be used at full power when powered from a conventional urban single-phase 220V / 50Hz network.

This article will consider the master oscillator for such a converter.

There are a great many different variations of schemes on this theme. And basically three-phase ZGs are built on microcontrollers, of course this is justified by the fact that the circuit is actually simplified to one case and several keys. On the face and gain in price and size.

But, the circuits built on the MK have one significant drawback, this is poor repeatability, since most radio amateurs and homemade ones, as a rule, do not know the science of writing programs and further microprocessor firmware, in most cases looking at the description of such a circuit and scratching their heads refuse to repeat.

When developing the circuit that is presented here, the task was to maximize simplicity, reliability and repeatability, as well as the availability of components.

The circuit creates a full-fledged three-phase signal at its 6 outputs with sustained fixed pauses (dead time) between pulses (this is necessary to prevent through currents through power switch transistors), to control three transistor half-bridges, in the diagonal of which a three-phase motor will be connected. But about the output part of the converter in the next article, and now we will consider the operation of the master oscillator.

(click to enlarge)

On the elements U1a ... U1d of the 4011BD chip, a pulse generator is built that sets the frequency of the generator.

Pulses from the clock generator are fed to the counting inputs of the 4017BD multiplexers.

The multiplexers are connected in such a way that their outputs create a shift register of 20 outputs, that is, a sequence of pulses running over 20 outputs, in order of priority. This is a kind of "plasticine" from which it is possible to form impulses of the required sequence for a 3-phase PN.

The basic signal requirements are

1. It is necessary to receive three pulses shifted relative to each other in time by 120 degrees, at three independent outputs of the MO.
2. It is also necessary to receive three more pulses, but already in antiphase to the first point.
3. Well, it would be very nice to get small pauses between pulses, the so-called death time (dead time).
This is necessary in order to exclude through currents on transistor switches that can disable them, since three half-bridges are used in the power section of the converter, in the diagonal of which the electric motor will be turned on. But more on that later, I only mentioned this part to make it clear what death time is for.

It is this signal that is "blinded" in the attached diagram.

To see how it all works live, I suggest downloading the MULTISIM 10 program on my website: elektron.ucoz.ru/load/1-1-0-25.

And here is the project file of the 3-phase generator for MULTISIM 10: elektron.ucoz.ru/statyi/1312.zi

You can run it and see how everything works and output waveforms.

To be continued! In the second part of the article, we will directly consider the power part of the 3-phase converter itself.

.lay board and project file for Multisim 10

Author: Artur (Lefty); Publication: cxem.net

See other articles Section Power supply.

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