Fast acting surge protection. Scheme, description

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ENCYCLOPEDIA OF RADIO ELECTRONICS AND ELECTRICAL ENGINEERING
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Fast acting surge protection. Encyclopedia of radio electronics and electrical engineering

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Encyclopedia of radio electronics and electrical engineering / Protection of equipment from emergency operation of the network

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Currently, various devices for protecting household appliances from high and low voltage in the 220 V network have appeared on the radio markets.

Unfortunately, all of them have significant drawbacks: low speed where the load is switched using a relay, no turn-on delay after operation due to a power surge (which is very important especially for switching power supplies of modern TVs and old-type refrigerators), limitation on switched load power.

Fast surge protection
Fig. 1

The proposed protection device (Fig. 1) is devoid of these shortcomings and works as follows. When the mains voltage goes beyond the set limits (the lower limit is regulated by resistor R4, the upper limit is R6), the timer DD2 is triggered and a low level is set at its output 3, the green LED VD6 goes out, the triac TC 106 disconnects the load. A low level at output 7 of the DD2 timer enables the operation of the DD1 K176IE5 counter, which essentially acts as a second timer that generates the delay time to turn on the load. This time depends on the ratings of R14 and C6 and, when indicated in the diagram, is about 4 minutes.

Fast surge protection
Fig. 2

After 4 minutes, a very short reset pulse of the DD5 timer passes through the differential circuit C15 R2 and T2 and, if the mains voltage returns to normal, a high level is set at pin 3 of the timer, the green LED lights up and the VD10 TC106 triac connects the load. Otherwise, another 4 minutes will pass and everything will repeat itself, and this will happen until the voltage in the network returns to normal.

The red LED VD7 indicates the operation of the timer on DD1 and, if everything is fine, should flash every 2-3 seconds.

There are no special requirements for details, with the exception of: R2 - power of at least 1 W, SZ - with a low leakage current. Optosimistor VD9 MOS 3022 can be replaced with MOS 3020-3062. Capacitor C1 - at least 400 V.

Through the TS-106 triac, you can switch a load of up to 10 A with an appropriate radiator, and if more current is needed, then you need to replace it with a more powerful one (for example, TS-132).

This protection is designed for round-the-clock operation and is only afraid of a short circuit at the output.

When you first turn on through protection, the load will be connected after 4 minutes, then - automatic operation.

Author: Evgeny Poyarkov, Pervomaisk; Publication: radioradar.net

See other articles Section Protection of equipment from emergency operation of the network.

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