# Three-Phase Induction Motor Slip Calculator

Compute three-phase induction motor slip: synchronous speed n_s = 60·f/p and slip s = (n_s − n)/n_s. Supports slip-from-speed and speed-from-slip modes; automatically flags generator mode (s < 0).

> Canonical page: https://elysiatools.com/en/tools/motor-slip-calculator

- **Category:** Math & Numbers

- **Keywords:** induction motor, slip, synchronous speed, rotor speed, three-phase, asynchronous motor, pole pairs, motor speed, electrical engineering

## Overview

The Three-Phase Induction Motor Slip Calculator computes synchronous speed, rotor speed, and slip for asynchronous motors. By inputting the supply frequency, number of pole pairs, and either the measured rotor speed or the slip fraction, you can quickly analyze motor performance and automatically identify generator operating modes.

## Inputs

- **Solve Mode** (select)
- **Frequency f (Hz)** (number): Supply frequency in Hz (50 Hz or 60 Hz are most common).
- **Pole Pairs p** (number): Number of POLE PAIRS p (not total poles). A 4-pole motor has p=2; a 6-pole motor has p=3.
- **Rotor Speed n (rpm)** (number): Required for Slip-from-speed mode. Enter the measured rotor speed in rpm.
- **Slip s (0–1)** (number): Required for Speed-from-slip mode. Enter slip as a fraction (0.04 means 4%).
- **Decimal Places** (number)

## When to use

- When analyzing three-phase induction motor performance using nameplate parameters and measured rotor speed.
- When calculating the expected rotor speed of an asynchronous motor based on a target slip percentage.
- When verifying if an induction machine is operating in motor mode or generator mode under specific load conditions.

## How it works

- Select the solve mode to calculate either slip from rotor speed or rotor speed from slip.
- Enter the electrical supply frequency in Hz and the number of pole pairs (for example, enter 2 for a 4-pole motor).
- Input the measured rotor speed in rpm or the slip value as a decimal fraction, then specify the desired decimal precision.
- The calculator computes the synchronous speed using the formula n_s = 60·f/p and solves for the missing variable, flagging generator mode if the slip is negative.

## Use cases

- Determining the slip of a 4-pole, 50 Hz motor operating at a measured speed of 1440 rpm.
- Calculating the expected shaft speed of a 6-pole, 60 Hz motor with a rated slip of 5%.
- Identifying regenerative braking or generator operation when a motor is driven above its synchronous speed.

## Frequently asked questions

### What is the difference between poles and pole pairs?

Pole pairs (p) represent half the total number of magnetic poles. A 4-pole motor has 2 pole pairs, and a 6-pole motor has 3 pole pairs.

### How does the calculator determine if the motor is in generator mode?

If the measured rotor speed is higher than the synchronous speed, the calculated slip becomes negative (s < 0), indicating generator operation.

### What unit should I use for the slip input?

Slip must be entered as a decimal fraction between 0 and 1. For example, enter 0.04 to represent a 4% slip.

### Can this calculator be used for single-phase induction motors?

Yes, the synchronous speed and slip formulas apply to single-phase induction motors as well.

### What are typical slip values for standard induction motors?

Standard full-load slip values typically range from 0.01 (1%) for large motors to 0.05 (5%) or more for smaller motors.

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