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 Requirements
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.
Full Load Amperage (FLA)
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
- Load/torque requirements
- Efficiency of the siting of the motor
Other parameters that have influence over the current trace include
- Power factor,
- Speed control, and
- Cooling.
Therefore, electrical motors power demand and current consumption depend on size, type, and operational conditions of the equipment.
It recommended that one should refer to the motor properties to obtain the correct values of voltage, power, and current at various working conditions.