Electrical Industry Article

Three-phase motors run our industrial economy, powering everything from conveyor lines and pumps to lathes and fans. These devices have been a part of assembly plants and other industrial settings for generations and they can run for 15 years or more when installed correctly and maintained over time. That’s why meter manufacturers have developed products specifically to help facilities staff and outside contractors understand their operation. Specialty meters, like phase sequence and open phase indicators are among the tools that motor pros can call on to safely verify units are properly wired.

Phase sequence meters can help ensure motors are installed so that they’re rotating in the correct direction. Of course, this can also be determined by simply running the motor before it’s connected to its load, but this can be a time-consuming, hit-or-miss approach. Phase sequence indicators can take the guesswork out of this process before connections are made.

Open phase meters can detect single-phasing conditions, making them good tools for ensuring correct installation and for troubleshooting when problems do occur. Single phasing is one of the more common problems motors can face. It occurs when one of the motor’s line connections isn’t connected, which leads to the motor operating on a single phase. This situation can lead to overheating and related motor damage, and can have a number of possible causes, including:

• Damaged contacts in the motor starter
• Open windings
• Open wiring connections
• Open fuses or circuit breaker poles

Including phase sequence and open phase indicators in your toolbox can help ensure motor-installation success and help understand and address any problems. And, to make these measurements easier – and your toolbox less crowded, some manufacturers have combined these functions into a single, handheld device.