Synchronous Motor Speed Calculator

Synchronous Motor Speed Formula:

\[ \text{Speed (RPM)} = \frac{120 \times \text{Frequency (Hz)}}{\text{Number of Poles}} \]

Synchronous Speed:

Unit Converter ▲

Unit Converter ▼

From:	To:

1. What is Synchronous Motor Speed?

Synchronous speed is the speed of the rotating magnetic field in the stator of an AC motor. It depends on the frequency of the power supply and the number of poles in the motor. This speed is called "synchronous" because the rotor turns at the same speed as the magnetic field.

2. How Does the Calculator Work?

The calculator uses the synchronous speed formula:

\[ \text{Speed (RPM)} = \frac{120 \times \text{Frequency (Hz)}}{\text{Number of Poles}} \]

Where:

120 — Constant derived from converting seconds to minutes and accounting for poles
Frequency — AC power supply frequency (typically 50Hz or 60Hz)
Poles — Number of magnetic poles in the motor (always an even number)

Explanation: The formula shows that motor speed is inversely proportional to the number of poles - more poles means slower rotation.

3. Importance of Synchronous Speed Calculation

Details: Knowing the synchronous speed is essential for motor selection, performance analysis, and troubleshooting. It helps determine if a motor is operating at its designed speed or if there are synchronization issues.

4. Using the Calculator

Tips: Enter the power supply frequency in Hz and the number of poles (must be an even number). Common pole numbers are 2, 4, 6, or 8 for most industrial motors.

5. Frequently Asked Questions (FAQ)

Q1: Why is the number of poles always even?
A: AC motors require pairs of north and south poles to create the rotating magnetic field, so pole count is always even.

Q2: What's the difference between synchronous and actual motor speed?
A: In induction motors, the actual speed is slightly less than synchronous speed (called slip). Only synchronous motors run exactly at synchronous speed.

Q3: What are typical synchronous speeds for 50Hz and 60Hz systems?
A: For a 2-pole motor: 3000 RPM (50Hz) or 3600 RPM (60Hz). For a 4-pole motor: 1500 RPM (50Hz) or 1800 RPM (60Hz).

Q4: Can I use this for DC motors?
A: No, this formula only applies to AC synchronous motors. DC motor speed depends on voltage and other factors.

Q5: How does variable frequency affect motor speed?
A: Speed is directly proportional to frequency - increasing frequency increases speed proportionally.