ECN Forum Forums General Topics of the Trade General Discussion Area Manual Y-Delta starter.....

That surge or spike is very visible if you have a analogue ammeter in the motor circuit.
It will be 3 or 4 times Inom.

Yes, but the spike of a direct line start will be even worse!

Worse still, a 7.5HP 440v motor winding up a 120lb planer cutterblock to 4500rpm from a Delta start.
I fitted a clutch. Never mind the machine getting damaged, my ruddy nerves were shot to shreds!

Alan

For some more information on the star delta starter, see http://www.lmphotonics.com/star_delta.htm

Best regards,

After 3 more phone calls, visited with customer today.

He's had 2 other electricians in; one blew up the start button and the 3 phase on/off switch, the other verified the motor (10HP) is good.

I proposed deleting the entire Y-Delta stuff, and doing it in a more traditional way:
60A 3 Phase breaker in panel
60A disconnect on wall - for LOTO
#10 feed into control box (Motor FLA is 29.5) - or do I need #8 ? 80% ?
SQ D contactor with B70 heaters and start stop station in control box
Use existing 3 phase contactor (relay) for 3A coolant pump - control via 208 Single pole switch).

Comments appreciated.