79 relay for motor protection
79 relay for motor protection
(OP)
I've read from ANSI DEVICE NUMBER that 79 relay is an AC Reclosing Relay. at this,I would ask some questions.
1. could you describe about the construction of 79 relay?
2. how does this relay work?
3. do you think this relay effective to prevent the motor from trip due to voltage dip due to short circuit fault?
4.which do you think is more effective? installing 79 relay or installing a UPS?
1. could you describe about the construction of 79 relay?
2. how does this relay work?
3. do you think this relay effective to prevent the motor from trip due to voltage dip due to short circuit fault?
4.which do you think is more effective? installing 79 relay or installing a UPS?





RE: 79 relay for motor protection
If you are experiencing contactor drop-out or chatter due to voltage dip, use of UPS power for the contactor control power is one possible solution. But this has its own drawbacks, especially when the UPS fails.
David Castor
www.cvoes.com
RE: 79 relay for motor protection
And dpc is right that a 79 relay isen't a correct application for a motor circuit.
RE: 79 relay for motor protection
Reclosing a motor circuit with the timings typical of a recloser has a high probability of causing severe mechanical damage. Bent or broken shafts, sheared keys in keyways, exploded couplings, stators turning in the housings, damage to machines by excess torque, either positive or negative and other damage related to sudden transient torque are possible with fast reclosing of a motor circuit. The bigger the motor the worse it gets.
A reclosing lockout would be more suitable.
Bill
--------------------
"Why not the best?"
Jimmy Carter