How to Calculate Servo Stabilizer Capacity
- Published 03 Jun, 2026
- 7 min read
Servo stabilizer sizing starts with connected load, but the final capacity should also consider starting current, diversity, load growth, fluctuation range and site conditions.
Basic sizing approach
For three-phase industrial loads, estimate kVA from the connected kW and power factor. A simplified estimate is kVA = kW / power factor. For motor-heavy plants, include starting conditions and future expansion instead of sizing exactly at present running load.
Practical example
If a production line has 80 kW connected load at 0.8 power factor, the apparent load is approximately 100 kVA. A buyer may select a higher standard rating after considering starting current, voltage correction range and future load additions.
Important factors
- Actual running load versus nameplate load
- Motor starting current and drive behavior
- Input voltage fluctuation range
- Single-phase or three-phase load balance
- Ambient temperature and enclosure location
- Future capacity expansion
FAQs
Should stabilizer capacity match transformer capacity?
Not necessarily. It should match the protected connected load and operating conditions, not simply the upstream transformer rating.
Can undersizing damage the stabilizer?
Yes. Undersizing can cause overheating, overload trips and reduced equipment life.
How much spare capacity should a servo stabilizer have?
A 15 to 25 percent margin is a common starting point, but motor starting current, input voltage range, load growth and duty cycle may require a different margin.
Should motor starting current be included in stabilizer sizing?
Yes. Direct-on-line motors, compressors and pumps can draw high starting current, so the starting method, acceleration time and simultaneous starts must be assessed.
Does a wide input voltage range affect stabilizer capacity?
Yes. Low input voltage can increase current and thermal stress. Confirm the usable output capacity and any derating across the full specified input range.
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