Single phase or 3-phase motor for blower
Single phase or 3-phase motor for blower
(OP)
I am considering buying a small regenerative blower (1 HP)
and default option is 1-phase motor. I want to control the speed using variable frequency controller.
Is there any advantage of getting 3-phase motor here?
Thanks,
Nick
and default option is 1-phase motor. I want to control the speed using variable frequency controller.
Is there any advantage of getting 3-phase motor here?
Thanks,
Nick





RE: Single phase or 3-phase motor for blower
David
RE: Single phase or 3-phase motor for blower
When we took the display to an actual show, the blower kept popping breakers. You pay big bucks for a 15A circuit at a show, and much bigger bucks for bigger circuits.
I got a scopemeter and a current sensor and measured what was going on. The starting current peaked around 48A, and stayed above 30A for quite a while as the blower got up to speed.
Luckily, it was a dual- voltage motor, so I was able to kluge up a timer and a relay to start the motor with reduced current in one leg. After 6s or so, it was rotating feebly, but fast enough to limit the peak current to ~39A, which the show breakers tolerated.
If I had it to do over again, and had the spending priority that an upcoming show allows, I'd order a 3 phase motor (same price) and a smart drive (now under $200, but then nearly $1000) that could accept 115V/1/60 in and produce 230/3/variable out, and ramp the motor start so the supply wouldn't see much of a transient above the steady state 7A or so.
Mike Halloran
Pembroke Pines, FL, USA
RE: Single phase or 3-phase motor for blower
Nick
RE: Single phase or 3-phase motor for blower
I can't believe I disregarded start-up surge (that is typically 6-10 times steady-state current). The VSD add-a-phase technology has indeed made small hp 3-phase motors reasonable.
David
David Simpson, PE
MuleShoe Engineering
www.muleshoe-eng.com
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.
The harder I work, the luckier I seem
RE: Single phase or 3-phase motor for blower
Mike,
Not sure how you get 230/3/variable from a 115/1/60 input unless you have a transformer in there. More common is (say) 230/1/50 in, 230/3/variable out.
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RE: Single phase or 3-phase motor for blower
Using a drive would allow you to "soft start" the motor. Another possibility would be to close a damper on the input side of the blower (or cover it with cardboard etc) while starting. That won't reduce the magnitude of the inrush and starting current but it will substantially reduce its duration.