motor nameplate information #6 – Construction

This information is very useful when we selected the electric motor.From this data we can estimate the type of motor and the suitable application to ensure it running full capacity and more efficiency.

This is a basic data that we can get from electric motor name plate.Normally it tell about enclosure,motor frame,and bearing.This information can make we easier to rectify any problem when motor is defected.

Example we can know the size and type of bearing used for that motor.We can know the information without dismantle the motor.Only from the nameplate of motor.

Motor construction

Here i explain detail about motor construction information :

  • Enclosure

This designation, often shown as “ENCL” on a nameplate,classifies the motor as to its degree of protection from its environment, and its method of cooling. In MG 1, NEMA describes many variations. The most common are Open Drip-Proof (ODP) and Totally Enclosed Fan Cooled (TEFC).

1) ODP

An open drip-proof motor allows a free exchange of air from outside the motor to circulate around the winding while being unaffected by drops of liquid or particles that strike or enter the enclosure at any angle from 0 to 15 deg downward from the vertical.


A totally enclosed fan cooled motor prevents free exchange of air between inside and outside the motor enclosure. It has a fan blowing air over the outside of the enclosure to aid in cooling.

3) Explosion-proof

These are variations of totally enclosed motors that are for use in Division 1 hazardous atmospheres as defined in Article 500 of the National Electrical Code (NFPA-70). The enclosure designation on the nameplate is typically TEFC (or TENV; that is, Totally Enclosed Non-Ventilated).

The only indication that the motor is suitable for the hazardous atmosphere is a UL label indicating the atmosphere in which the motor may be applied, and a temperature code designation.

Explosion-proof motors must contain any explosions of the specified atmosphere inside the motor. Moreover, they won’t let the surface temperature exceed the limits of the temperature code even at fault conditions such as overload or locked rotor.

  • Frame

The frame size sets important mounting dimensions such as foot hole mounting pattern, shaft diameter, and shaft height. NEMA standards do not set some dimensions that can turn out to be important if the motor must fit into a confined space.

Some examples of frame designation :-

1) 445T.

This motor is a modern standard T-Frame motor. Critical mounting dimensions for all manufacturers are as defined in NEMA Standard MG 1.

2) 445TC.

This T-Frame motor has a standard NEMA-defined C face.

3) 445TD.

This T-Frame motor has a standard NEMA-defined D flange

4) 445U.

The dimensions of a U-Frame motor are defined by NEMA standards prior to 1965. The U-Frame is the predecessor to the present T-Frame motor, and typically it has the equivalent horsepower capability of a T-Frame motor that is two frame sizes smaller.

The first two digits of the frame size divided by 4 defines the height of the shaft ~center line from the bottom of the feet. Thus, the shaft height of a 445T motor is : 44 / 4 = 11 in.

The third digit in the frame size determines the distance between the foot holes nearest the shaft and the opposite drive-end foot holes.

For further standard designations refer to NEMA Mg. 1- 11.01.

  • Bearings

Some manufacturers use a simplified designation simply indicating the bearing size and type,for example, 6309 for a size 309 ball bearing.It may use special bearings and elect to display their own bearing part numbers on the nameplate.

Many special bearings are applied in motors for reasons such as high speed, high temperature, high thrust, or low noise.Your must understand the motors’ bearing requirements.


  1. It would be very useful if you add noload current,power factor or no load loss to check after rewinding a motor.

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