# What are the key factors that determine the power requirements of an electric motor?

Electrical motors have certain power demands that depend with the electrical motor size, kind, and application.

These considerations result in the flow of current through the electric motor ranging from fraction of an ampere to as high as few tens of amperes.

## Power Rating

Generally, electric motors are specified in horse power (HP) or kilo watt (KW).

Residential motors typically can vary from 1/4 HP, (about 0. 18 kW) up to several HP where the application is larger.

## Voltage

Motors can be utilized on different voltage classes and may comprise of 120V, 240V, or 480V amongst other classifications.

## Efficiency

The efficiency of the motor determines the power it uses up. It means motors with higher efficiency will consume fewer currents for the rated output power.

## Current Draw

Current drawn is normally directly proportional to the motor’s power demands but is generally higher in motors with high power ratings; more so when they are loaded. The rated voltage and horsepower information can be used to estimate or Full load current.

The amount of current drawn by a motor in their maximum condition is expressed in terms of Full Load Amperage (FLA). This value can usually be stated on the motor’s label. For example:

• A 1 HP motor at 120V might take approximately 15A.
• Thus a 1 HP electric motor at 240 volts may be taking about 7. 5 amps.
• Bigger motors such as the 5 HP motors can also demand higher current, probably more than 20 amps in the 240V circuits.
• Thus, motors in the 1-10 HP range may take from 5 to 50 A at 230V, whereas large industrial motors can take several hundreds of A.

## Starting Current

Electric motors pull a much heavier current during starting as compared to the FLA this is 5 to 7 time the FLA.

This inrush current is considered a quite important factor concerning the circuit design and the choice of circuit breaker.

## Application-Specific Variations

It was evident that the current at the onset was different than the maximum current able to be sourced at the output of the converter unit under no load conditions. In the case of a lighter load on the motor, it will be expected to pull less current as compared to maximum loading.

In general, the power requirements of an electric motor depend on factors like

• Motor size/horsepower rating
• Operating voltage