When to use this calculator
Find synchronous rotating-field speed from frequency and pole count. Pole count must be an even integer. Induction-motor loaded speed is lower by slip.
Explore the ac power & reactance calculators for other questions in this topic. For a related calculation, use the Power Factor Angle Calculator: Convert a sinusoidal displacement power factor into phase-angle magnitude.
PUTTING IT INTO PRACTICE
Motor Synchronous Speed: a worked example
The values below are an illustrative example, not a recommendation. Replace them with measurements or assumptions that match your question.
| Input | Example value |
|---|---|
| Supply frequency (Hz) | 50 |
| Magnetic poles (integer) | 4 |
| Result | 1,500 rpm |
- Check the input labels and enter the example values above.
- Apply the relationship: Synchronous speed = 120 × frequency/pole count.
- The result is 1,500 rpm, rounded for display.
How to interpret your result
Pole count must be an even integer. Induction-motor loaded speed is lower by slip.
Use RMS values in the AC power relationships. Apparent power is measured in VA and real power in watts. Pure-sine conversions and balanced three-phase equations only apply under their stated assumptions.
Frequently asked questions
Why can volt-amps differ from watts?
Apparent power is the RMS voltage-current product, while real power also reflects power factor. They are numerically equal only at a power factor of one.
When is the motor synchronous speed calculator useful?
Find synchronous rotating-field speed from frequency and pole count. Pole count must be an even integer. Induction-motor loaded speed is lower by slip.
How do I use the motor synchronous speed calculator?
Enter supply frequency (hz), magnetic poles (integer). The result updates automatically. Use the units shown beside each input; the example values illustrate the method.
Which formula does this calculator use?
Synchronous speed = 120 × frequency/pole count.
What should I check before using the result?
Pole count must be an even integer. Induction-motor loaded speed is lower by slip.
How are results rounded?
Scalar numbers display up to six decimal places, with scientific notation for very large or small values. Text, fraction, date and schedule outputs use the format described on the tool. Intermediate calculations use JavaScript floating-point arithmetic. Keep sensible precision for your measurements.
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