I have posted a few mains voltage stabilizer circuits in this blog, these units are made and meant for preserving the connected appliances at their outputs. In spite of this these equipment lack one protection which is the overload protection.
A specific stabilizer unit might be rated for managing an optimum stipulated limit of power, beyond which it’s impacts may begin diluting or may turn out to be ineffective. Overloading a voltage stabilizer may also lead to heating of the transformer and fire dangers.
An easy circuit demonstrated below might be integrated with a stabilizer circuit or any such protection circuit for strengthening the preserving features of the units.
The diagram demonstrates a very easy and uncomplicated configuration where only a few transistors and few other passive parts are utilized for developing the intending design.
The mains stabilized AC is comprised of the stabilizer outputs and permitted to switch by means of another RL1, via its N/C contacts.
One of the wires of the AC mains connections is added with a series resistor of a calculated value.
As the load across the mains output raises, a proportionate magnitude of voltage commences generating across this resistor.
The value of the resistor is so chosen that the voltage across it gets to be simply enough to illuminate a associated LED as a reaction to a load that may be viewed as harmful and over the maximum bearable limit.
At this point, the LED just illuminates, an LDR placed and enclosed ahead of the LED quickly falls its resistance as a reaction to the illumination produced by the LDR.
The unexpected decrease in the resistance of the LDR, switches ON T1 which often switches ON T2 and the relay, starting the latching impact of the circuit and the relay.
The load or the appliance at the output is thus instantly turned off when an overload circumstance is identified.
The entire activity happens within a fraction of a second, offering no opportunity for any untoward result and the whole process is safeguarded by the inclusion of this easy AC mains overload protection circuit.
R1 = 1.5/I(specified current limit), example if I=15amps, then (R1 = 1.5/15 = 0.1 Ohms)