Power Quality
How to Calculate the Required Servo Stabilizer Capacity
Servo stabilizers are normally specified in kVA. Calculate the simultaneous apparent power, then check starting demand and the manufacturer’s operating limits.
Calculate running kVA
For a single-phase load: kVA = V × I / 1000. For a balanced three-phase load: kVA = √3 × line voltage × line current / 1000. If electrical input kW and power factor are known, kVA = kW / PF. Motor shaft kW must first be divided by efficiency to estimate electrical input kW.
Worked example
A balanced load drawing 100 A at 415 V requires approximately 71.9 kVA. An illustrative 20% allowance gives 86.3 kVA before selecting a supported rating. This allowance is an example, not a universal sizing rule.
Check transient and input conditions
Add only loads expected to operate together, allow for agreed future expansion and verify starting current, duration and permitted voltage dip. Confirm full output capacity at the lowest input voltage and site temperature with the supplier.
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