How to Size an Overload Device for a Motor

In this video, Keith will walk you through the calculations necessary to size overload devices for motors. We'll go over external and internal overload devices such as starters, overload relays and VFDs. Check this video out if you have been looking for a solution to your motor overload problems. If you don't know how to install or where to buy overload protection devices check this video out and click the links in the description. If you are looking to calculate your electrical overload rating for your motors this video may also interest you. And if you ever wanted to see a motor light on fire, check out 5:42! Buy an overload protection device: https://www.emotorsdirect.ca/controls Contact us: https://www.emotorsdirect.ca/contact-us Supporting articles: https://www.emotorsdirect.ca/knowledge-center/article/how-to-protect-your-motor-against-overload https://www.emotorsdirect.ca/knowledge-center/article/replacing-an-overloaded-motor https://www.emotorsdirect.ca/knowledge-center/article/what-causes-motor-overload 0:00 Introduction 0:53 Recap On Motor Overload 1:38 External Overload Devices 1:40 Overload Relays & Starters 2:08 VFDs 2:23 Internal Overload Devices 2:41 Electrical Rating Calculations 5:42 Motor Overload Time Lapse 5:55 Conclusion Formulas: If service factor is greater than or equal to 1.15, multiply the FLA by 1.25 If service factor is less than 1.15, multiply the FLA by 1.15 If SF is unknown, multiply the FLA by 1.15 The maximum setting or rating for the overload protection device is X amps. In cases where your electric motor setup has reduced voltage starting, specifically in wye/delta start motors, the max overload setting will be calculated based on the phase current and not on the line current. The motor starts in the wye configuration and then switches to the delta configuration once the motor gets up to speed. The current draw is different in each configuration, so the max overload will be set based on the phase current. This means that you have one additional calculation to complete before you can calculate the max overload setting. You will use the line current to calculate the phase current. Phase current is about 57.7% of the line current. In wye/delta start motors: FLA * 0.577 = X X * 1.15 = Y amps The maximum setting or rating for the overload protection device is Y amps.