motor nameplate information #1 – Electrical Input

The important information that we can see on motor nameplate is a electrical input.From this we can know what the voltage for motor,the suitable frequency,full load ampere,type of connection ( star or delta ),power factor and others.

We can collected the data for induction motor from name plate.This information is very important to troubleshooting or rectify any problem happen about that motor.

This information is critical items to ensure we install the right motor ans suitable with our application.Ok,i explain the detail about electrical input for induction motor that we can found on name plate.

Electrical input

  • Voltage

The voltage at which the motor is designed to operate is an important parameter.Standard voltage for motors built to NEMA MG 1 (1987) are defined in MG 1-10.30.The voltage rating assumes that there is voltage drop from the network to the motor terminals.

  • Frequency

Input frequency is usually 50 or 60 Hz.When more than one frequency is nameplated, other parameters that will differ at different input frequencies must be defined on the nameplate.

  • Phase

This represents the number of AC power lines supplying the motor. Single and three-phase are the norms.

  • Current

Rated load current in amps is at nameplate horsepower (HP) with nameplate voltage and frequency.Review both motor and drive for a matched system regarding
current on AFD applications.

  • Code

A letter code defines the locked rotor kVA on a per-hp basis.Codes are defined in MG 1-10.37.2 by a series of letters from A to V.Generally, the farther the code letter from A, the higher the inrush current per hp. A replacement motor with a “higher” code may require different upstream electrical equipment, such as motor starters.

  • Type

Some manufacturers use “Type” to define the motor as single or poly phase, single or multi speed, or even by type of construction. Type is of little use in defining a motor for replacement purposes unless you also note the specific motor manufacturer.

  • Power factor

PF or PE  is the ratio of the active power (W) to the apparent power (VA) expressed as a percentage. It is numerically equal to the cosine of the angle of lag of the input current with respect to its voltage, multiplied by 100. For an induction motor, power factor also varies with load.The nameplate provides the power factor for the motor at full load.

  • Capacitor correction

The nameplate may list the maximum power factor correcting capacitor size.The number would indicate capacitor value in kilovars. A value greater than that suggested may result in higher voltages than desired and could cause damage to the motor or other components.

  • Motor terminal connection

It show about motor connection terminal for that motor such as delta or star connection.It also state the voltage for the connection.From that we can determine what type of connection and suitable voltage that we can supply to operate that motor.


  1. Why the no load current,a very useful parameter,is not indicated in the name plate?. It is a guide to size a capacitor for PFC and to check the no load current after rewinding a motor.

  2. krishna says

    wat is meant by frame size , which is given in nameplate of an motors

  3. It would be useful to include no load/locked rotor current,noise level,starting capacitor size(to reduce starting current), PFCC size, vibration level too. In every motor windings if three thermistors,one for each phase are embedded, it would save money and copper by facilitating monitoring of winding temperature before a winding burns.
    To the thermistor a thermometer should be able to be mounted either on the motor body or in switchboard

  4. In 3 phase electric motors if name plate is not available , how to find which 3 leads input and which 3 leads ouput terminals.

    any test ?

    • Use multimeter to find the pair of each continuity function.the pair of winding must have connection.If no continuity it is not the pair of winding.
      U1-U2 = continuity
      V1-V2 = continuity
      W1-W2 = continuity

  5. zonaid hasan says

    is there any way to determine the rotor current coz most of the equations needs it?
    thank you.

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