# How Does Voltage Unbalance affect a 3 Phase Induction Motor?

**URL:** <https://forumautomation.com/t/how-does-voltage-unbalance-affect-a-3-phase-induction-motor/14271>\
**Category:** Electrical\
**Tags:** motor\
**Created:** [July 23, 2026, 2:16pm UTC](https://forumautomation.com/t/how-does-voltage-unbalance-affect-a-3-phase-induction-motor/14271 "2026-07-23T14:16:54Z")\
**Posts on this page:** 1\
**Page:** 1

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**Author:** ![Rabert](https://forumautomation.com/user_avatar/forumautomation.com/rabert/32/6784_2.png) [@Rabert](https://forumautomation.com/u/Rabert)\
**Post date:** [July 23, 2026, 2:16pm UTC](https://forumautomation.com/t/how-does-voltage-unbalance-affect-a-3-phase-induction-motor/14271/1 "2026-07-23T14:16:55Z")

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## How Does Voltage Unbalance affect a 3 Phase Induction Motor?

## Why Voltage Unbalance Important?

Even a small voltage unbalance can significantly reduce the performance and lifespan of a **[3 phase induction motor.](https://forumelectrical.com/3-phase-ac-motor-alternating-current-motor-troubleshooting/)**

Because current unbalance is much greater than voltage unbalance, the motor experiences excessive heating and mechanical stress.

## Motor Derating due to Voltage Unbalance

3% voltage unbalance: Motor should be derated to approximately 90% of its rated capacity.

5% voltage unbalance: Allowable motor load may need to be reduced to around 75% of its rated capacity.

## Effects of Voltage Unbalance

- Increased winding temperature
- Reduced motor efficiency
- Higher vibration and torque pulsations
- Faster insulation deterioration
- Shortened motor service life

Maintaining balanced three-phase voltages is essential for reliable motor operation, improved efficiency, and longer equipment life.

 ![1 - Copy](https://cdn.forumautomation.com/original/2X/c/c49e6a53ebca5077bde2e15e08f6df5632252def.jpeg)

Regular voltage monitoring helps prevent

- Overheating,
- Unexpected failures and
- Costly downtime.