1. What is Electric Motor Speed?

Definition: The rotational speed of an electric motor, typically measured in revolutions per minute (RPM).

Purpose: Understanding motor speeds helps in selecting the right motor for applications like pumps, fans, and machinery.

2. How Does the Calculator Work?

The calculator uses the synchronous speed formula:

Where:

• 120 — Constant for converting frequency to RPM
• Frequency — Electrical supply frequency (typically 50Hz or 60Hz)
• Poles — Number of magnetic poles in the motor (always even number)

Note: Actual motor speed will be slightly less (2-5%) due to slip in induction motors.

3. Common Motor Speed Standards

For 60Hz systems:

• 2-pole motor: ~3600 RPM
• 4-pole motor: ~1800 RPM
• 6-pole motor: ~1200 RPM
• 8-pole motor: ~900 RPM

For 50Hz systems:

• 2-pole motor: ~3000 RPM
• 4-pole motor: ~1500 RPM
• 6-pole motor: ~1000 RPM
• 8-pole motor: ~750 RPM

4. Using the Calculator

Tips: Enter the electrical frequency (typically 50 or 60 Hz) and select the number of poles from the dropdown.

5. Frequently Asked Questions (FAQ)

Q1: Why do motors have different pole numbers?
A: More poles create slower speeds but higher torque, while fewer poles allow higher speeds with less torque.

Q2: What's the difference between synchronous and actual speed?
A: Synchronous speed is theoretical; actual speed is slightly less due to "slip" in induction motors (typically 2-5% less).

Q3: How do I know how many poles my motor has?
A: Check the nameplate RPM or divide 7200 by the RPM (for 60Hz) - e.g., 3600 RPM = 2 poles.

Q4: Can motors run at variable speeds?
A: Yes, with variable frequency drives (VFDs) that adjust the input frequency.

Q5: What's the fastest possible AC motor speed?
A: For 60Hz, the maximum synchronous speed is 3600 RPM (2-pole); for 50Hz, it's 3000 RPM.