dual speed 400hp, 480VAC motor

[pmover]

fellow engr's,

bear with this gearhead...

existing 400hp, 480VAC electric motor driven by VFD (0-1800 rpm).

in the event of vfd failure, is it desired to operate motor at 50% speed (900 rpm). best speed for maintaining controlability with process. this means instead of a 4-pole motor for VFD operation, an 8-pole motor for direct line voltage operation.

is this possible? a single motor with 2-windings or poles.

thanks for educating a gearhead.
-pmover

 

[jraef]

Yes, but it will mean a new motor. Buy a 2 speed 2 winding (2S2W) motor because the power circuit is simpler for interfacing with a VFD. You will still need to isolate the 2 power systems (VFD and Electro-mech) so there will be a lot of contactors and interlocks necessary, but there is no reason why it cannot be done. Find a good VFD integrator and explain the problem to them. Don't go with someone who does not understand the intricacies of mixing VFD and Line power to motors. You can blow out the VFD if it is done wrong, and a 400HP VFD is nothing to triffle with.

"Venditori de oleum-vipera non vigere excordis populi"

 

[panelman]

sounds to me like the best way out might be to get a standby drive

 

[pmover]

jraef and panelman,

thanks for the responses.

yes, various standby drive units are being considered along with fluid drive couplings, magnetic couplings, etc.

there is a balance in meeting process conditions and what is most practical for situation.

a follow-up question, if selecting 2S2W motor, will motor footprint change as well? - depends upon motor mfg? trying to determine if foundation work needs to be accomplished.

thanks!
-pmover