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POWER

Transformer Calculator

Voltage · Turns ratio · Current · Power · Impedance — ideal & practical

Vp/Vs = Np/Ns Pp = Ps

Voltage & Turns Ratio

Enter any two values — the rest will be calculated

V
V
turns
turns
Turns ratio (Np/Ns) — ratio
Voltage ratio (Vp/Vs) — ratio
Primary voltage (calculated) — V
Secondary voltage (calculated) — V
Vp / Vs = Np / Ns

Transformer schematic

Vp Vs Iron core Np Ns
Ideal transformer: Vp/Vs = Np/Ns

Transformer basics

  • Step-up: Ns > Np, Vs > Vp
  • Step-down: Ns < Np, Vs < Vp
  • Ideal: Pp = Ps (no losses)

Current & Power

Enter voltages, currents or power to solve

V
V
A
A
W
Primary current (Ip) — A
Secondary current (Is) — A
Apparent power (S) — VA
Primary power — W
Secondary power — W
Vp/Vs = Is/Ip  |  Pp = Ps

Power balance

Pp Ps Ideal: Pp = Ps
In an ideal transformer, primary and secondary power are equal

Transformer sizing

Estimate kVA rating for a given load

V
A
PF
%
Apparent power (S) — VA
kVA rating — kVA
Recommended kVA — kVA
Real power (P) — W
S = V × I  |  kVA = S / 1000

kVA sizing guide

1k 5k 10k 25k 50k 100k
Standard kVA sizes shown — pick next size up