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Mr. Saravanan

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Mr. Thamizh



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15 Aug 2018

Name Plate Details of an Electric Motor

We have all seen the motor nameplate attached on the motor side (or on top). All motors have a permanent nameplate which lists all important data; further data is usually available in the motor catalogue.

The name plate of the motor provides important information necessary for proper identification, ordering, replacement and application.


1.         Voltage

2.         Frequency

3.         Phase

4.         Current

5.         Type

6.         Power factor

7.         KW or Horsepower

8.         Full-load speed

9.         Efficiency

10.        Duty

11.        Insulation class

12.        Maximum ambient temperature

13.        Altitude

14.        Enclosure

15.        Frame

16.        Bearings





Electrical input



This data tells you at which voltage the motor is made to operate. Nameplate-defined parameters for the motor such as power factor, efficiency, torque and current are at rated voltage and frequency. When the motor is used at other voltages than the voltage indicated on the nameplate, its performance will be affected.



Usually for motors, the input frequency is 50 or 60 Hz. If more than one frequency is marked on the nameplate, then other parameters that will differ at different input frequencies have to be indicated on the nameplate as well.



This parameter represents the number of AC power lines that supply the motor. Single-phase and three-phase are considered as the standard.



Current indicated on the nameplate corresponds to the rated power output together with voltage and frequency. Current may deviate from the nameplate amperes if the phases are unbalanced or if the voltage turns out to be lower than indicated.



Some manufacturers use type to define the motor as single-phase or poly-phase, single-phase or multi-speed or by type of construction. Nevertheless, there are no industry standards for type. 


Power factor

Power factor is indicated on the nameplate as either “PF” or “P .F” or cos f . Power factor is an expression of the ratio of active power (W) to apparent power (VA) expressed as a percentage. Numerically expressed, power factor is equal to cosine of the angle of lag of the input current with respect to its voltage.

The motor’s nameplate provides you with the power factor for the motor at full-load.



Mechanical Input


kW or horsepower

kW or horsepower (HP) is an expression of the motor’s mechanical output rating – that is it’s ability to deliver the torque needed for the load at rated speed

Full-load speed

Full-load speed is the speed at which rated full-load torque is delivered at rated power output. Normally, the full-load speed is given in RPM. This speed is sometimes called slip-speed or actual rotor speed





Efficiency is the motor’s output power divided by its input power multiplied by 100. Efficiency is expressed as a percentage. Efficiency is guaranteed by the manufacturer to be within a certain tolerance band, which varies depending on the design standard, eg IEC or NEMA.



This parameter defines the length of time during which the motor can carry its nameplate rating safely. In many cases, the motor can do it continuously, which is indicated by an S1 or “Cont” on the nameplate. If nothing is indicated on the nameplate, the motor is designed for duty cycle S1.





Insulation class

Insulation class (INSUL CLASS) is an expression of the standard classification of the thermal tolerance of the motor winding. Insulation class is a letter designation such as “B”or “F”, depending on the winding’s ability to survive a given operating temperature for a given life. The farther in the alphabet, the better the performance.

For instance, a class “F” insulation has a longer nominal life at a given operating temperature than a class “B”.


Maximum ambient temperature

The maximum ambient temperature at which a motor can operate is sometimes indicated on the nameplate. If not the maximum is 40°C for EFF2 motors and normally 60°C for EFF1 motors. The motor can run and still be within the tolerance of the insulation class at the maximum rated temperature.



This indication shows the maximum height above sea level at which the motor will remain within its design temperature rise, meeting all other nameplate data.

If the altitude is not indicated on the nameplate, the maximum height above sea is 1000 metres.






Enclosure classifies a motor as to its degree of protection from its environment and its method of cooling. Enclosure is shown as IP or ENCL on the nameplate



The frame size data on the nameplate is an important piece of information. It determines mounting dimensions such as the foot hole mounting pattern and the shaft height. The frame size is often a part of the type designation which can be difficult to interpret because special shaft or mounting configurations are used



Bearings are the component in an AC motor that requires the most maintenance. The information is usually given for both the drive-end (DE) bearing and the bearing opposite the drive-end, non drive- end (NDE).



Reference // Electrical Engineering Portal

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