auto changeover from generator to mains

Posted on Feb 5, 2014

Because of energy crisis Load shedding may be a common problem in several countries. Sudden power fluctuations, surge and high voltage may spoil sophisticated household appliances like TV, VCR, VCP and music system. This circuit provides protection against these problems and automatically changes the power supply from Generator output to mains sup

auto changeover from generator to mains
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ply and also switches off the generator. This circuit is self explanatory. When lines supply voltage crosses the preset level, Zener diode ZD4 break down and thus transistor T2 conducts, T3 does not conduct, causing the relay to de-energise. Voltage surge at the time of power resumption is protected by the delay circuit around transistor T1. All the portable petrol and kerosene generators have a connection from CDI. To stop the engine of the generator-set, this connection is to be grounded momentarily (through the switch). This lead is to be connected with the ground through the N/C point of the relay. Instead of the one transformer, two transformers are used in series to ensure better life of the unit. Value of capacitor C2 can be increased or decreased for the variation of delay time. A negative feedback resistance, R6 (15 K-ohm to 100 k-ohm) can be incorporated between transistor T3 and T4 to overcome the damage that could be caused by voltage fluctuations.

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