Relay Type Voltage StabilizersA relay type voltage stabilizer is one of the most popular types of voltage stabilizers. Circuits of such stabilizers are based on transformer taps commutating with the help of electronic commutators. The maximum output voltage of the stabilizer significantly exceeds that of a power transformer. The required transformer capacity needs to be selected based on the minimum possible voltage within the given power network. For example, if the minimum possible network voltage is at least 180 V, the transformer needs to add an extra 40 V, that is the value 5.5 times lower than the network voltage. This is exactly by how much the output capacity of a stabilizer would exceed the capacity of a power transformer (of course, this is without considering the transformer's efficiency, and the maximum possible current allowed through the switching elements).The voltage at the output of a stabilizer changes stepwise. The number of voltage regulation steps usually doesn't exceed 3-6, which enables sufficient accuracy in maintaining the output voltage. When calculating the number of rings in the transformer's winding for each step the voltage in the power network is assumed as equal to the voltage of triggering the switching element.Usually electromagnetic relays are used as commutators. Then the circuit is rather simple and reproducible. The only drawback is that when the relay switches, there appears an arch, which destroys the contacts.In circuits that are more complex, for example, in those using digital elements, the relay is switched, when the network's halfwave passes through zero, which prevents generation of a spark. But it's either the relay needs to be very quick, or the devices need to be turned on when the previous halfwave declines.The overall advantages of relay-type voltage stabilizers are as follows:Firstly, high stabilization accuracy that is directly proportionate to the number of steps and keys.Secondly, there is no distortion in voltage shape, since the distorting elements are missing.Thirdly, the wide working temperature range.Forthly, high noise immunity, since the relay is not affected by noise, voltage or current shapes.Fifthly, low sensitivity to network frequencies.And, finally, the low price.

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