Induction Motor Torque-Speed Characteristic (Kloss)

Induction Motor Torque-Speed Characteristic (Kloss) | Online Free Tool | Elysia Tools

Tool usage guide

Learn when to use this tool, what it supports, and how real users apply it.

Key facts

Category: Math & Numbers
Input types: number, select
Output type: json
Sample coverage: 4
API ready: Yes

Overview

This induction motor torque-speed characteristic calculator allows you to model and analyze the mechanical performance of a three-phase induction motor using the Kloss equation. By entering basic motor nameplate data such as frequency, pole pairs, rated power, and rated speed, the tool computes critical parameters including rated torque, breakdown (maximum) torque, starting torque, and breakdown slip, while generating a detailed, sampled torque-speed (T-n) curve.

When to use

When designing or selecting a three-phase induction motor and you need to estimate its torque-speed curve from nameplate data.
When analyzing motor startup behavior and verifying if the starting torque is sufficient for a specific load.
When calculating the breakdown slip and maximum overload capacity of an induction motor under varying frequency or pole configurations.

How it works

1Enter the supply frequency, number of pole pairs, rated power, and rated rotor speed from the motor's nameplate.
2Specify either the maximum torque directly or provide an overload factor to determine the breakdown torque.
3The tool calculates the synchronous speed, rated slip, rated torque, breakdown slip, and starting torque.
4It applies the Kloss equation to generate a sampled torque-speed curve containing your preferred number of data points.

Use cases

Generating torque-speed data points to plot motor characteristics in external engineering reports or simulation software.
Verifying motor overload margins by comparing rated torque against breakdown torque using the overload factor.
Estimating the starting torque (at zero speed/slip of 1) to ensure the motor can start under heavy load conditions.

Examples

1. Analyzing a 7.5 kW 4-Pole Industrial Motor

Electrical Machine Designer

Background

An engineer needs to document the torque-speed profile of a standard 7.5 kW, 4-pole induction motor operating at 50 Hz with a rated speed of 1440 rpm.

Problem

The engineer needs to find the rated torque, breakdown torque, starting torque, and breakdown slip to verify load compatibility.

How to use

Set frequency to 50 Hz, pole pairs to 2, rated power to 7.5 kW, rated speed to 1440 rpm, and overload factor to 2.5. Set curve points to 21.

frequency: 50, poles: 2, powerUnit: 'kW', ratedPower: 7.5, ratedSpeed: 1440, overloadFactor: 2.5, curvePoints: 21

Outcome

The tool calculates a rated torque of 49.7359 Nm, a breakdown torque of 124.3398 Nm, a breakdown slip of 0.1917, and a starting torque of 45.9713 Nm, along with 21 curve coordinates.

2. Evaluating a 15 kW Motor with High Overload Capacity

Industrial Plant Engineer

Background

A plant engineer is replacing a conveyor motor and needs to evaluate a 15 kW, 4-pole motor at 50 Hz with a rated speed of 1460 rpm and a high overload factor of 2.8.

Problem

The engineer needs to determine if the starting torque and breakdown torque are sufficient to handle peak conveyor startup loads.

FAQ

What is the Kloss equation used for?

The Kloss equation is an analytical formula used to approximate the torque-speed (or torque-slip) relationship of an induction motor based on its maximum torque and breakdown slip.

How is the number of pole pairs related to the number of poles?

The pole pairs parameter (p) is half the total number of poles. For example, a standard 4-pole motor has 2 pole pairs.

What is breakdown slip?

Breakdown slip (or pull-out slip) is the slip value at which the induction motor produces its maximum (breakdown) torque.

Can I input the maximum torque directly?

Yes, you can enter the maximum torque in Nm. If left blank, the tool will automatically calculate it using the provided overload factor.

What range of sample points can I generate for the curve?

You can configure the tool to sample between 11 and 41 points along the torque-speed curve.

frequency: 50, poles: 2, powerUnit: 'kW', ratedPower: 15, ratedSpeed: 1460, overloadFactor: 2.8, curvePoints: 21

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Examples that match this tool

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Learn when to use this tool, what it supports, and how real users apply it.

Key facts

Overview

When to use

How it works

Use cases

Examples

1. Analyzing a 7.5 kW 4-Pole Industrial Motor

2. Evaluating a 15 kW Motor with High Overload Capacity

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