Most of the time, the motor nameplates do not contain the number of poles data on them. The number of poles in a motor can be calculated from its synchronous speed and its rated frequency. Here is a simple synchronous number of poles calculator.
Number of poles calculator in a motor
| Synchronous speed | |
| Rated frequency | hz |
Result | |
| Number of poles | RPM |
How to use the number of poles calculator:
The above tool requires following data for calculation:
- The rated synchronous speed of the motor. (Mandatory)
- The rated supply frequency. (Mandatory)
After entering the required data from the nameplate, click on the “Calculate” button to find out the number of poles.
The rated speed of the motor is mentioned in RPM. In order to find out the synchronous speed roundup the values mentioned on the nameplate to the nearest value in the table below:
| Speed at 50Hz | Speed at 60Hz |
|---|---|
| 3000 | 3600 |
| 1500 | 1800 |
| 1000 | 1200 |
| 750 | 900 |
| 600 | 720 |
| 500 | 600 |
| 375 | 450 |
| 250 | 300 |
Number of poles calculation
The following formula can be used for the calculation:
![\[ Number \mspace{4} of \mspace{4} poles =\frac{ 120 \times f }{n_s} \]](https://www.electricalclassroom.com/wp-content/ql-cache/quicklatex.com-a52ad1f5936e07f2a5164d10f388ba6a_l3.svg "Rendered by QuickLaTeX.com")
Where,
- f: Supply frequency
- ns: Synchronous speed
Therefore the synchronous speed of a motor is directly proportional to the supply frequency and inversely proportional to the number of poles in the motor.
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