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)
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:
- Measure the resistance R of the heater coil using multi meter.
- 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
- Also see: Difference Between Voltage and 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
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.
