The Price of Overheating Motors

In this series of posts on Predictive Maintenance, we will discuss:

A mechanical plant’s productivity relies on keeping all the many moving parts running, which is dependent on the health of the plant’s electric motors. In the past, motors were specified at power levels well above the needs of the plant, greatly reducing the risk of motor failure and allowing for a long motor life. But this strategy is not energy-efficient. To run efficiently and save on electricity costs, today’s motors are closely matched to their power requirements. Unfortunately, this makes motors much more susceptible to overheating. As such, motors need to be carefully managed to avoid thermal overloads that damage the motor’s insulation and lead to premature aging and motor burnout.

Is your motor overheating?

Locked shaft conditions, high inertial loads, single-phasing, and under-voltage problems can all damage a motor. Each of these conditions lead to overheating, which can both cause damage to the insulation—which increases the likelihood of equipment issues in the future—and damage to the motor itself. Under these conditions, bearings can also be damaged due to lubrication failure.

Frequent starts and stops are a common danger to motors. Starting an induction motor creates a rush of current 10 to 20 times greater than what the motor experiences during normal use, causing hot spots that can damage windings or insulation[1]. It is important to wait for the motor to cool down sufficiently before restarting. The consequences of starting the motor when it’s too hot can cause permanent damage to insulation and/or windings which may result in costly repairs or even replacing the motor.

Damaged stator windings from overheating*

Severe damage is likely if a motor exceeds its temperature limit by even a few degrees. Running 10°C above its rated temperature cuts a motor’s lifespan in half[2]. When it comes to such expensive equipment, you don’t want to have to buy a replacement sooner than you expected. This equipment is a significant investment, and you want it to keep operating smoothly for as long as possible, ideally over its rated operating life. It’s also important to avoid motor failures that could lead to lengthy, unexpected downtime. Any time the line is down is wasted time, cutting into the plant’s profit.

When it comes to motors, overheating can be costly. It’s important to take steps to prevent overheating from occurring.

Read the next post in our five-part series to learn how temperature monitoring can become part of your maintenance strategy.

[1] https://www.pumpsandsystems.com/topics/instrumentationcontrols/calculating-pump-starts-and-cycle-time

[2] https://www.efficientplantmag.com/2003/04/overheating-electric-motors-a-major-cause-of-failure/

*Image sourced from: https://e2e.ti.com/blogs_/b/motordrivecontrol/archive/2016/04/22/how-to-detect-insulation-failures-in-electrical-equipment-part-1 on Nov 10, 2017.


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