Voltage Regulator Selection

1. Capacity safety factor

Automatic Voltage Regulator takes the output apparent power (kVA) as the nominal rated capacity. In general, the load is not purely resistive, that is, the power factor COS￠≠1. The actual active power that the automatic voltage stabilizer can output is kW=capacity (kVA)×COS￠. Therefore, when actually selecting, it is necessary to reasonably select a voltage-stabilized power supply according to the rated power, power factor and load type of the electrical equipment. The output power should have an appropriate margin, especially when selecting impact loads. The margin should be larger. The specific selection safety factor is shown in the table below

Load nature Equipment type Safety factor Select voltage-stabilized power supply capacity

Pure resistive load Incandescent lamps, resistance wires, electric furnaces and other equipment 1.25~1.5 1.25~1.5 times the total load power

Inductive and capacitive loads Fluorescent lamps, fans, motors, water pumps, air conditioners, computers, refrigerators, etc. 2 ~ 3 ≥2~3 times the total load power

In the environment of large inductive and capacitive loads (such as motors and computers), the starting current of the load should be considered to be particularly large (up to 5~8 times the rated current) when selecting, so the capacity of the automatic voltage stabilizer should be 2.5~3 times the load power.
For example: 1 three-phase motor of 2.2kW and 1 5.5kW. When selecting a voltage stabilizer, the capacity should be ≥ (2.2kW + 5.5kW) × 2.5 = 19.25 kVA, that is, a voltage stabilizer of at least three-phase SJW-20 kVA or above should be selected.

2. Output capacity curve of non-compensated voltage stabilized power supply

When the input phase voltage of the automatic voltage stabilizer (single-phase 0.5kVA~3kVA, 10k horizontal and below, three-phase 9kVA and below) is lower than 198V, the output capacity begins to decrease; when the input phase voltage is equal to 160V, it drops to 50[%] of the rated capacity of the voltage stabilizer. Therefore, special attention should be paid to reducing the load and derating at the low end of the power supply voltage to avoid overloading and burning the voltage stabilizer;

The automatic voltage stabilizer can output 220V and 110V voltages at the same time. But even when all outputs are 110V, the load carried by the voltage stabilizer cannot exceed 50[%] of the rated capacity, otherwise it is overloaded.
3. Application of voltage stabilizer

Voltage stabilizers are widely used in industrial and mining enterprises, schools, hospitals, post and telecommunications, oil fields, railways, construction sites, hotels, scientific research departments, and other places where stable power supply voltage is required, such as electronic computers, computer tomography (CT), precision machine tools, precision instruments, test equipment, elevator lighting, imported equipment and production lines. It is also suitable for users at the end of low-voltage distribution networks with low or high power supply voltage and large fluctuations, and electrical equipment with large load changes. It is especially suitable for all places with high requirements for grid waveforms.

4. Basic principles of voltage stabilizers

The voltage stabilizer circuit consists of a voltage regulating circuit, a control circuit, and a servo motor. Most voltage stabilizers achieve voltage stabilization by moving carbon brushes. When the input voltage or load changes, the control circuit samples, compares, and amplifies the voltage divider resistor, and then drives the servo motor to rotate, so that the position of the voltage regulator carbon brush changes, and the output voltage is kept stable by automatically adjusting the coil turns ratio. Voltage stabilizers with larger capacity also work on the principle of voltage compensation.
5. Main parameters of automatic voltage stabilizer

Project: single-phase, three-phase (three-phase four-wire system, separate regulation)

Input voltage range of voltage stabilizer: 160V~250V, phase voltage: 160V~250V

Line voltage: 280V~430V

Output voltage of voltage stabilizer: 220V or 110V, phase voltage: 220V, line voltage: 380V

Overvoltage protection value of voltage stabilizer: 246V±4V, phase voltage: 246V±4V (based on phase voltage)

Line voltage: 426V

Voltage stabilizer voltage accuracy: ±3[%]