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Motor Current Ratings

by James Krier

Not every motor is the same

Wed, Jan 5th 2011 04:00 pm

We receive several calls each week asking us for power requirements on different machines that we produce. This chart will should be used only as a guide and is not intended to be 100% accurate for every motor.  For a more precise number please refer to the motors name plate. Amperage will fluctuate depending on several factors.  These factors include but are not limited to input voltage, motor rpm, and motor brand.

For example a 1.5 HP Baldor motor turning 3450 rpm draws 13.4 amps on 120 volt service. A Leeson brand motor of the same specification list 12.4 as its running amperage.  The 1.5 HP Baldor motor that turns at 1725 will draw 18 amps according to its name plate.

motor current / amp chart

The information in this chart was derived from Table 430-148 & 430-150 of the NEC and Table 50.1 of UL standard 508A. The voltages listed are rated motor voltages. The currents listed shall be permitted for system voltage ranges of 110-120, 220-240, 380-415, 440-480 and 550-600 volts. The full-load current values are for motors running at usual speeds and motors with normal torque characteristics. Motors built for especially low speeds or high torques may have higher full-load currents, and multi-speed motors will have full-load currents varying with speed. In these cases, the nameplate current ratings shall be used. Caution: The actual  motor amps may be higher or lower than the average values listed above. For more reliable motor protection, use the actual motor current as listed on the motor nameplate. Use this table as a guide only