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Definition: Nameplate

Copyright© 1996 by Brian L. Boley. All Rights Reserved.

Motor nameplates are provided by virtually all manufacturers to allow users to accurately identify the operating and dimensional characteristics of their motors years after installation. The nameplate is usually a metal plate, secured by a pair of screws or rivets, and is generally located on the side of the motor. (Expert maintenance technicians will tell you that the nameplate is always located on the side of the motor where the nameplate is most difficult to read!)

The following criptic information will usually be stamped into the nameplate (stamping is used because it doesn't wear off as ink tends to do. Unfortunately, the lack of contrast can make it difficult to read. Sometimes, a little bit of dirty oil or grease applied to the nameplate and then wiped "smooth" puts the dark substance into the indentations of the stamped letters and allows for easier reading.).

Nameplate Terms

  • Motor Manufacturer
  • Mod. (Model), Tp. (Type), or Cat. (Catalog)
  • Ser. (Serial Number)
  • HP (Horsepower) or KW (kilowatts)
  • RPM (Revolutions per Minute)
  • V (Volts)
  • ARM. (Armature)
  • FLD. (Field)
  • (Phases)
  • Hz (Hertz or Cycles per Second)
  • A (Amps)
  • Fr (Frame)
  • Enc. (Enclosure)
  • CW (Clockwise Rotation) or CCW (Counter-Clockwise Rotation)
  • (Delta Winding)
  • (Star or Wye Winding)

  • Motor Manufacturer

    This is the tradename of the company which manufactured the motor. If you are lucky, the company's home city, and perhaps even an address and/or telephone number will be on the nameplate.

    Mod. (Model), Tp. (Type), or Cat. (Catalog)

    Some companies distinguish between a Model number and a Type number. (I don't know why). In any event, this is the key number that you need if you want to contact the manufacturer.

    Ser. (Serial Number)

    Serial numbers are important because they often contain "date codes". This is information which helps the manufacturer determine when the motor was manufactured. Since many motors have multiple revisions through their lifecycle as the manufacturing process (hopefully) improves, this helps determine which set of drawings to use -- and lets the technical people at the manufacturer help you quicker and more accurately.

    HP (Horsepower) or KW (kilowatts)

    If you are using an American made motor or an older English or Canadian motor, it will probably be rated in Horsepower. European and Asian motors are usually rated in kilowatts -- unless they have been designed for export to the American market.

    Rule to remember: 1 HP = 3/4 KW (more precisely 746 watts).

    Second rule to remember: Volts x Amps = Watts.

    RPM (Revolutions per Minute)

    The number of times each minute that the shaft turns on its axis. This is rated at the Hertz listed. Typical values are 1750, 1450, 3450, etc. If more than one speed is listed, this indicates a multi-speed motor. Note that AC inverter drives can change the speed of a motor from its rated speed.

    V (Volts)

    The operating voltage of the motor. If the motor is an AC motor, this will typically be 115, 230, 380, 480, 575, or some number reasonably close to these figures. DC motors will have numbers such as 24, 48, 90, 180, or other voltage, and will usually say "VDC".

    ARM. (Armature)

    This is the maximum voltage which can be applied to the armature of a DC motor. Typical values are 90 or 180 VDC. An amperage will often be listed.

    FLD. (Field)

    This is the voltage which should be applied to the field of a DC motor. Typical values are 100, 150, 200 VDC. An amperage will often be listed.


    This will indicate whether the motor operates from single phase or three phase electricity.

    Hz (Hertz or Cycles per Second)

    This indicates whether the motor is designed for operation on 50 or 60 Hertz electricity. Motors consume about 15% more amps when operated at 50 Hertz than at 60 Hertz. Thus, most 50 Hertz-designed motors will operate on 60 Hertz systems with little difficulty, but you will pay more for this.

    A (Amps)

    The amount of current consumed by the motor.

    Fr (Frame)

    The physical dimensional standard to which the motor adheres. This is critical when it is necessary to locate a mechanical replacement for an old motor.

    Enc. (Enclosure)

    This is the degree of protection offered by the enclosure. Common terms are TEFC, TEBC, TENV, ODP, TEAO, etc.

    CW (Clockwise Rotation) or CCW (Counter-Clockwise Rotation)

    When facing the motor from the shaft end, this is the direction of rotation of the motor (if the motor is unidirectional).

    (Delta Winding)

    Many motors have two different ways of connecting the windings to three phase power. The delta winding usually gives higher speed with lower starting torque. In essence, this is cruising gear.

    (Star or Wye Winding)

    Many motors have two different ways of connecting the windings to three phase power. The delta winding usually gives higher starting torque with lower top speed. In essence, this is first gear.

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