Lab-View Controlled Relays for 480V

[Florasga]

Good evening,

I'm currently working in instrumenting an electrical motor test bench that is going to be used to test a specific Electrical Motor. This bench works with 480 V line fed motors and I was looking forward to shut them ON and OFF using some LabView controlled relays. I currently have an 8 slot Ethernet cDAQ with a Digital I/O module. I was looking to see if someone, based on past experience or personal knowledge, could help me on which hardware could be the most useful in order to control the powering of the motors. I saw NI has a relay board module that is usable on cDAQ but i'm not sure if this is the best way to go or if it be useful at all for such high voltages.

Thank you in advance for your time and help.

[Sam_Sharp]

I think you need to find some suitable HV - many have a coil/activation voltage of 24V which you could use with some of the NI Digital Output modules (9375 rings a bell) providing the current requirements of the relay coils are low enough (with a suppression diode).

Failing that, you would need to have an intermediate stage - using some external switching circuitry (e.g. mosfets) that can supply enough current to energise the relay coils.

Obviously there are some pretty serious safety concerns with switching such high voltages so you'll need to think very carefully to ensure it is adequately isolated / insulated. Make sure you follow any local regulations relating to electrical safety etc.

[johnsold]

You should only use suitably rated motor contactors to control the motors. They are specifically designed to handle the motor starting currents, stall current, overvoltage transients on opening the contacts and so on. Once you have selected suitable contactors, then figure out how to drive them. You could use a relay output module to control the contactor coils or a digital output to drive a solid state relay which in turn drives the contactor coils.

DO NOT TRY TO RUN YOUR MOTORS BY SIMPLE RELAYS.

Lynn