Single Phase VFD - SURPRISE!!!

I was just looking on the Drives Warehouse website to see if they had any of the 5HP Spedestar VFDs in stock, and I punched in the worng search
parameter. I found a pleasant surprise. They are listing Spedestar 1ph - 3ph VFDs upto 30HP now. Those big ones aren't cheap (not outrageously expensive either), but it opens up a world of options in used equipment for those of us running home shops or for folks running small shops that don't have 3 phase power other than buying or building a big noisy rotary phase converter.
The last time I looked the largest I found for 1ph-3ph was 5HP.
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Something to keep in mind with 1-phase in 3-phase out VFD's is that above a certain motor horsepower (5 I think) you need to derate the VFD by 50%.
We found this out when ordering the VFD for our 7.5 HP lathe - needed a 15 HP drive for it.
I don't remember the parameter that was the problem but the sales guy made a convincing argument at the time.
Our VFD source for Westinghouse / Teco drives was dealerselectric.com
Carla
We are drowning in information but starved for knowledge. -- John Naisbitt, Megatrends
On 10/21/2015 7:16 PM, Bob La Londe wrote:

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On Thu, 22 Oct 2015 18:33:16 -0700, Carla Fong

That's true if it's a 3-phase input VFD being used on single phase. For VFD's designed for 1-phase input, it's already taken into account in the rating. I have a little 1 Hp, 220V single phase in, 3-phase out Rockwell like that.
Pete Keillor

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On 10/23/2015 4:26 AM, Pete Keillor wrote:

That explains it - The drive we got was a 3-phase input that could also accept single phase input with the output derated 50%.
Thanks for the memory jog!
Carla
"If you can't fix it with a hammer, you've got an electrical problem."

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On 10/21/2015 10:16 PM, Bob La Londe wrote:

On the Polyspede site http://www.polyspede.com/?p )0 they show single phase 240v Spedestar drives to 50 hp/57 kva (!).
Now 57 kva from 240v is 238 amps, so one would need some pretty serious wiring for that baby.
Even 10 hp (12.4 kva) is 51 amps
Bob
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On Wed, 21 Oct 2015 19:16:21 -0700, Bob La Londe wrote:

Speaking purely as a circuit designer who's never even seen a VFD in real life:
The biggest limit to making a really good 1ph to 3ph VFD is going to be getting a dependable DC rail internally, which, in turn, depends on getting reliable, cost-effective capacitors that can store the requisite energy and handle the requisite power. Basically, you need something in there that'll tide you over for the four milliseconds or so, twice each electrical cycle, where there's not enough voltage available from the socket to bring you joy.
Capacitors have been coming down in price, and circuits to do things like getting that nice DC rail have been getting figured out (and enabled by ever-fancier electronics in ever-smaller packages).
So it's probably inevitable that prices would be down and availability up.
--

Tim Wescott
Wescott Design Services
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