In India, however, the specified voltage for domestic use is 230 V but more commonly this voltage fluctuates. It is sometimes very low or very high. Since the motor, relay and other accessories are designed to operate very efficiently at one particular voltage, so it is necessary to maintain the voltage applied to the refrigerator, as constant as possible. Whereas the low voltages cause overloading of the motor, high voltage may effect the capacitor. Most of the time when the motor or relay of the unit is damaged, it is due to high or low voltage because the result of high or low voltage is excessive current flow.
Fig. 1: Fridge Voltage Stabilizer (Refrigerator Stabilizer).
To stabilize the voltage, a voltage regulator or voltage stabilizer is used with domestic refrigerators. The voltage regulator may be manual or automatic. In manual voltage regulator, one has to check the voltmeter reading and adjust it. This is simply a tap-changing transformer. The automatic voltage regulator employs relays and other electronic circuitry which automatically keeps the output voltage within very narrow range. The generally available automatic voltage stabilizers are of the following ranges:
|
Input voltage |
Output voltage |
Capacity |
| 165 to 280 volts | 220 to 240 volts | 0.5 KVA |
| 135 to 280 volts | 220 to 240 volts | 0.6KVA |
The automatic regulator is costly as compared to the manual but is more advantageous because it automatically takes care of the refrigerator during nighttime and other periods of neglect. The voltmeter of such regulators, need not to be switched on all the time. The 1 shows the outlook of an automatic voltage stabilizer and Fig. 2 shows the block diagram of its circuitry.
Fridge Voltage Stabilizer (Refrigerator Stabilizer) Block Diagram
Fig. 2: Fridge Voltage Stabilizer (Refrigerator Stabilizer) block diagram.
The 230 V/50 V supply is given to an autotransformer and also to the auxiliary transformer, which operates relays. The autotransformer can provide step-up or step-down voltage according to the need. The auxiliary transformer is a step-down transformer of rating 230 V/12 V. It has an output current of 500 mA to operate the relays. The rectifier rectifies output ac from the auxiliary transformer to be fed to the relay system. The rectifier’s output is given to a circuit, which operates relays. This has two NPN transistors that operate respective relays.
The relay system has two relays each having a voltage setting of 12 V. The relays have one normally open and one normally closed contact. The output of each relay is connected to the autotransformers tapping. The output is taken from the autotransformer and connected to the output socket of the stabilizer.