5KV Motor Schematics

[kody916]

I happened to come across 5KV motor schematics for the first time. I noticed bunch of relays on the motor schematic drawing. ON DELAY Relay, OFF DELAY Relay and REACCELERATION relay. Anyone familiar with these relays and why do we use these relays for medium voltage motor. I know it has to do with protection but cant seem to find the definitive answer. would anyone help please

Thanks

 

[Phil Corso]

Kody...

Those terms relate to the Restarting of motors (in specific sequence) following a momentary interruption of power. It is not just for MV motors

Do you want additional detail?

Regards, PhilCorso

 

[kody916]

Kody...

Those terms relate to the Restarting of motors (in specific sequence) following a momentary interruption of power. It is not just for MV motors

Do you want additional detail?

Regards, PhilCorso

Sure I would love to. I have also attached the schematic I was talking about. Hope it will help

 

[Phil Corso]

Kody...

Send me your e-mail address, and I will send a document (rather ancient) that explains "Re-acceleration", with an example of a setup for an HPI Plant!

BTW, long before computers it was done with the installation of two plug-in relays for each MCC cubicle for LV motors and for each Swgr cubicle for HV motors!

Phil Corso

 

[Jraef]

I see two issues with that circuit. Yes, the Off-Delay timer is the re-acceleration timer, but the On-Delay once (STR) is likely for staggered starting. Every MV starter probably has one in it and each one is set to a different time value so that when power is restored, they can't all be re-started at the same time.