Generally speaking, a voltage stabilizer can be chosen on the basis of just a few elements. Once this info has been established, any other optional requests can be considered separately.
1. Number Of Phases.
The number of phases of a voltage stabilizer depends on the type of load:
Single-phase load: single-phase voltage stabilizer.
Combination of several single-phase loads or three-phase loads: three-phase voltage stabilizer or a single-phase voltage stabilizer on each load.
Three-phase load: three-phase voltage stabilizer.
2. Rated Voltage.
Always establish the rated voltage that is supposed to be present at the input and output of the voltage stabilizer. In case of three-phase systems, provide with the line-to-line voltage value. Since there are different rated voltages around the world, do not assume that the local rated voltage is automatically known.
3. Input Variation Range & Output Voltage Accuracy.
Choosing a voltage stabilizer with the right input variation range is important because if its input voltage range is exceeded, then its output will increase or decrease by the same amount by which it has gone "out of limit".
In situations where there is a good mains supply, a voltage stabilizer offering an input variation swing of ±15% will usually be more than acceptable, but in more remote locations, or countries where the national supply infrastructure is less developed, variations of ±20% or greater may be needed to be accommodated by the voltage stabilizer.
As a general rule, the greater the input voltage swing the voltage stabilizer needs to correct, the higher the price.
An output voltage to within rated accuracy of the preset output voltage is the norm when specifying a voltage stabilizer. If a lower output voltage accuracy can be accommodated by the load equipment, then the input voltage range can be extended proportionally. As the cost of the voltage stabilizer is linked to the input voltage range it has to handle, accepting a lower output accuracy may prove to be a more economical solution.
4. Rated Power.
Establish the power required to supply the load system and consider an extra safety margin for possible future expansion of the load you wish to protect over the medium to long term. Do not make the voltage stabilizer run with full load all the time. 80% load of full loading capacity is recommended, for example, a 100KVA voltage stabilizer, power factor is 0.8, then recommended loading capacity is 100*0.8*0.8=64KW.
In a voltage stabilizer, the power is expressed in kVA, whilst the load power is usually expressed in kW. 1KVA=0.8KW, 1KW=1.25KVA, 0.8 is the standard power factor.
kVA(1-ph) = load voltage x load current
kVA(3-ph) = √3 x (phase to phase load voltage) x (load current)
If the power factor and/or the load power in kW cannot be easily established, measure the absorbed currents. All the voltage stabilizers are designed for the maximum input current.
Above information is usually shown on the name plate attached to the equipment, otherwise you will need to consult the manufacturers of the equipment or take measurements. It is always recommended that you measure the loads true RMS value.
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