Power quality on 240 3ph 4 wire service

[jmbaca]

We just installed a new machine in our facility and have had problems with it shutting down. We have a 240 3ph 4 wire service. What we have had problems with is a phase reversal relay in the machine kicking out the starter. When you start the machine it may run for 1 min. or 20 min , but it will shut down. then at no predetermined time the machine starts up, it trips a phase reversal relay, and then once it decideds to reset itself it start again. From what I understand the relay is to kick out if the motor is wired to run backwards or if their is a large fluctuation in power or loss of phase. We have checked the service and have from what we can tell good solid power to the machine and no weak or loss phase. The manufacture says that we must have bad power service, any idea on what may be wrong or how to check it on the power to the machine? If you have a weak leg, would you have low voltage at that leg? Are the phase reversal relays prone to being sensitive?

 

[robbietan]

looks like you have a defective 'phase reversal relay'. the relay should be bypassed during the startup stage, since it is most likely that there will be a slight voltage unbalance before the motor goes to full speed.

 

[Bob NH]

You might check the article at this link to see if it may relate to your problem.
http://www.itic.org/archives/articl...computers_and_electronic_office_equipment.php