When selecting the capacity of a single-phase AC voltage regulator, we must first consider its electrical load, and then choose the capacity and size of the single-phase AC voltage regulator accordingly. If the capacity of the single-phase AC voltage regulator is chosen too large, it will not only increase equipment investment but also cause the transformer to be in an idle state for a long time. Without using its function and operation, reactive power loss will increase instead. However, if the capacity of the single-phase AC voltage regulator is chosen too small, it will cause the transformer to be in an overload state for a long time, which can easily burn out the transformer. Therefore, we must have a correct direction when selecting the capacity of a single-phase AC voltage regulator, which can greatly save resources and energy.
The selection of the capacity of a single-phase AC voltage regulator should also be based on economic capacity. Alternatively, if the load is an asynchronous motor, its capacity should be considered based on its comprehensive power. It is even possible to select the transformer capacity according to the total power close to lighting, and to select the capacity of the single-phase AC voltage regulator based on the total power of the actual peak load that may occur. Such considerations not only ensure that every household is guaranteed and every user can choose with confidence, but also facilitate resource conservation and reuse for society.
Selection method of voltage regulator
1. Capacity safety factor
The AC regulated power supply is rated based on its apparent power output (kVA). However, in general, loads are not purely resistive, meaning the power factor COSφ is not equal to 1. The actual active power output of the regulator is kW = capacity (kVA) × COSφ. Therefore, when selecting a regulator, it is necessary to consider the specific conditions such as the rated power, power factor, and load type of the electrical equipment. The output power should have an appropriate margin, especially for impact loads, where the margin should be even larger. The specific safety factors for selection are shown in the table below
Load characteristics, equipment type, safety factor, and selected capacity of regulated power supply
Pure resistive load: Incandescent lamps, resistance wires, electric furnaces, and other equipment. 1.25~1.5 times the total power of the load
Inductive and capacitive loads: fluorescent lamps, fans, electric motors, water pumps, air conditioners, computers, refrigerators, etc. 2 to 3 times ≥ 2 to 3 times the total power of the load
In environments with high inductive and capacitive loads (such as electric motors and computers), the starting current of the load should be considered to be particularly large (up to 5-8 times the rated current) during selection. Therefore, the capacity of the voltage regulator should be chosen to be 2.5-3 times the load power.
For example, if one 2.2 kW and one 5.5 kW three-phase motors are used, when selecting a voltage regulator, the capacity should be ≥ (2.2 kW + 5.5 kW) × 2.5 = 19.25 kVA, which means that a three-phase voltage regulator with a capacity of at least SJW-20 kVA or higher should be selected.
2. Output capacity curve of non-compensated regulated power supply
When the input phase voltage of the self-coupling voltage regulator (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 decreases to 50% of the rated capacity of the voltage regulator. Therefore, it is particularly important to reduce the load and use it at a reduced rating at the low end of the power supply voltage to avoid overloading and burning out the voltage regulator;
The self-coupling voltage regulator can simultaneously output two voltages: 220V and 110V. However, even when outputting entirely at 110V, the load carried by the voltage regulator cannot exceed 50% of its rated capacity; otherwise, it is being used overload.
Based on the current power consumption of most computers, which is around 350w, I suggest you consider using a power supply with a capacity of 8000w or higher
In addition, the capacity level of each single-phase AC voltage regulator should be reasonably selected according to national standards.
