Short answer: add up the connected load in kVA, add 20–30% for motor starting and future machines, and choose a stabilizer whose input range covers the lowest and highest voltage your site actually sees.
Step 1: Calculate the load
List every machine the stabilizer will feed. If nameplates show kW, convert to kVA by dividing by the power factor (typically 0.8): kVA = kW ÷ 0.8. Add them up.
Step 2: Add margin
Motors draw several times their running current at start. Add 20–30% headroom, more if large motors start together. Example: 40 kVA of machines → choose about 50 kVA.
Step 3: Know your voltage range
Measure or note the lowest and highest supply voltage across the day and season. The stabilizer's input range must cover it. A narrower range than your site's swing means the stabilizer cannot fully correct.
Step 4: Single phase or three phase
Single-phase stabilizers suit individual machines and offices. A three-phase stabilizer protects a full plant or three-phase machines. On three-phase supply with unbalanced voltages, ask for independent phase correction.
What else matters
- Correction speed – how fast it reacts (Unitech: up to 50 V/s)
- Efficiency – losses run all day (Unitech: up to 97%)
- Generator compatibility if you run on DG
- Service – carbon brushes and variacs need periodic checks
Unsure? Share your load list and voltage readings and a Unitech engineer will recommend the rating. See our servo stabilizers.