As a maintenance electrician, I'm sure you've been in the high-pressure situation of having to get a "failed" motor running ASAP. And, you probably had to use all the troubleshooting techniques you acquired and mastered over the years. Well here's a tried-and-true technique you can use that involves testing the contact quality on live starters. Sound odd or intriguing? It shouldn't. Remember, your typical 3-phase manual or magnetic motor starter has three sets of power contacts and three overload (OL) relays. When you energize a motor through these types of starters, equal currents theoretically should flow through each contact and OL relay. So, you can measure the voltage drop across each contact or OL relay pole and compare the readings with one another.
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