Simple motor rated current calculator with calculation steps

Motor rated current also known as full load amperes (FLA) of a motor is the maximum current the motor windings are designed to carry. Here is a simple motor rated current calculator.

Motor data input

Motor Type
Enter the motor rated voltageV
Enter the motor rated power
Enter the motor Efficiency95%
Enter the motor Power factor0.85

Calculated Values

Motor rated currentA

How to use the motor rated current calculator:

The above tool requires following data for calculation:

  1. Motor Type – Single-phase or three-phase. (Mandatory)
  2. Motor rated power in HP or kW. (Mandatory)
  3. Input supply voltage. (Mandatory)
  4. Motor Efficiency as per nameplate – (if known).
  5. Rated power factor (if known).

After entering the required data, click on the “Calculate” button to find out the required fuse rating, Circuit Breaker rating, contactor current rating, and overload setting.

The appropriate selection of fuses, circuit breakers, overload relay, cables, and other switchgear is necessary to protect the motor from damages. The motor full load current forms the basis for the selection of all these equipment.

Motor rated current calculation

For single phase AC motors

For single-phase motors, when kW is known:

    \[    F.L.C =\frac{P_k_W \times 1000}{Voltage \times cos \phi \times \eta} \]

For single-phase motors, when HP is known:

    \[    F.L.C =\frac{P_h_p \times 746}{Voltage \times cos \phi \times \eta} \]

For Three phase AC motors

For three phase motors, when kW is known:

    \[    F.L.C =\frac{P_k_W \times 1000}{\surd3 \times Voltage \times cos \phi \times \eta} \]

For three phase motors, when HP is known:

    \[    F.L.C =\frac{P_h_p \times 746}{\surd3 \times Voltage \times cos \phi \times \eta} \]

Where,

  • Voltage: The phase-to-phase voltage for a 3-phase supply.
  • Rating: The power rating of the motor in kW.
  • Power factor (cosΦ): The rated power factor of the motor.
  • Efficiency (η): The efficiency of the motor.

Single-phase motor rated current reference table:

110V AC220V AC240V AC
0.07 kW1/122.41.21.1
0.1 kW1/83.31.61.5
0.12 kW1/63.81.91.7
0.18 kW1/44.52.32.1
0.25 kW1/35.82.92.6
0.37 kW1/27.93.93.6
0.56 kW3/4115.55
0.75 kW1157.36.7
1.1 kW1.521109
1.5 kW2261312
2.2 kW3371917
3 kW4492422
3.7 kW5542725
4 kW5.5603027
5.5 kW7.5854138
7.5 kW101105550
Reference: https://www.rm-electrical.com/technical-resource/motor-current-charts/

Three-phase motor rated current reference table:

kWHP220V AC240V AC380V AC415V AC550V AC660V AC690V AC
0.11/80.320.300.190.170.130.110.10
0.18¼0.580.530.340.310.230.190.19
0.251/30.810.740.470.430.320.270.26
0.37½1.191.100.690.630.480.400.38
0.56¾1.811.661.050.960.720.600.58
0.7512.422.221.401.280.970.810.77
1.11.403.553.262.061.881.421.181.13
1.525433222
2.237744322
3410965433
3.75121176544
45131277544
5.571816109766
7.510242214131088
9.31230281716121010
101332301917131110
111436332119141211
151948442826191615
182358533431231919
222871654138282423
303897895651393231
37471191106963484038
45571451338477584846
557017816310394715957
7595242222140128978177
901152912661681541169793
110140355326206188142118113
130165420385243223168140134
150191484444280257183161154
*All the values above are approximated. The actual current may vary depending on the voltage, power factor, and motor efficiency.

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