AC DC Full Load Current Calculation Formula

Full Load current calculation of AC and DC machine:

AC Loads (Alternating current) :

Full Load current calculation 3 Phase Motor:

Power formula  KW (Kilo watts)

V= Voltage +/- 10 % in Volts

I= Full load current in Amps

Cos pi = power factor

KW = output power in Watts……. All are given at the name plate details.

  • I = P/ 1.732 X V X cos pi Amps

Full Load current calculation Single phase Motor:

P = V X I X Cos pi

V= Voltage +/- 10 % in Volts

I= Full load current in Amps

Cos pi = power factor

KW = output power in Watts……. All are given at the motor’s name plate details.

  • I = / V X cos pi Amps

Full Load current calculation Three phase Heater coil:

Power formula  KW

V= Voltage

I= Full load current in Amps

KW = output power in Watts……. All are given on the heater’s plate details.

  • I =1 / 1.732 * V * I Amps.

Full Load current calculation Single phase heaters:

Power formula  KW

V= Voltage

I= Full load current in Amps

KW = output power in Watts……. All are given on the heater’s plate details.

  • I = V X I Amps

Calculate through resistance:

  1. Measure the resistance R of the heater coil using multi meter.
  2. Use this formula

P = I^2 * R

  • I = square root of (P/R)

Also see: How to Calculate Voltage Drop

Full Load current calculation DC machine (DC Motor & DC generator):

DC => Direct Current

P= V X I

  • I = P/V amps, Where

V = E ± Ia Ra ± Is Rsh + brushes drop (shunt machine)

V = E ± Ia (Ra + Rsh) + brushes drop (series machine)

V = Supply Voltage

E = back emf

Ia = armature current

Ra = armature resistance

Is = Field current

Rsh = Field resistance

Back EMF e = (pi * N * P * Z / 60 A)

Pi= Magnetic Flux

N= speed of the machine

P = number of poles

Z = number of conductors

A = number of parallel paths

P = A for lab winding

A= 2 for wave winding

If you are a maintenance engineer, you must know this:

3 phase 415V, at 0.8 pf, 1 Hp motor full load current = 1.3 Amps.

1 Phase 230V, at 0.8 pf, 1 Hp motor full load current = 4 Amps.

Thanking You !!!! Have a Nice Day….

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