Running a Steff power feeder with 440v/3ϕ Dahlander motor

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Forum topic by srzsrz posted 05-01-2013 06:07 PM 1778 views 0 times favorited 5 replies Add to Favorites Watch
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37 posts in 1027 days

05-01-2013 06:07 PM

Topic tags/keywords: motor 3 phase

A Maggi power feeder showed up on local craigslist for a very reasonable price… but it comes with a funny motor. More specifically, it’s an IEC (metric) dual-speed 1hp 440V 3ϕ Dahlander (YY/Δ) motor. I understand that this particular type of motor is common on European equipment and cannot readily be rewired for a different voltage.

I think I figured out how to deal with this, but it’s all complex enough, and new enough to me, that I’d really appreciate if somebody could check to make sure I’ve understood it.

Looking around the internet, it seems that I need

  • A 1ϕ transformer to step up 110V or 220V to 440V and a 1ϕ→3ϕ converter that runs at 440V; or
  • A 1ϕ→3ϕ converter that runs at 110V or 220V and a 3ϕ transformer to step up to 440V; or
  • A 1ϕ transformer to step up 110V or 220V to 440V and capacitor-based contraption to get the motor running on 1ϕ.

I understand that the last option is supposedly not very good for the motor, and that it’s going to require understanding the possibly rather complex Dahlander 2-stage starter and its wiring, and that one really ought to get some sort of 1ϕ→3ϕ converter, which could be

  • A commercial VFD (“variable phase drive”); or
  • A 3ϕ motor (“rotary phase converter”=RFC) with a little auxiliary 1ϕ motor to help it start; or
  • A 3ϕ motor (“rotary phase converter”=RFC) with some capacitor-based contraption to help it start.

Furthermore, in my understanding…

  • The modern power standard is ±120V, not ±110V, but I’m wishfully assuming that the “440V” rating on the nameplate really just means “4 times standard residential voltage.” If that is not the case, I assume that would plead in favor of using the VFD, which I believe can usually be configured to step down the voltage a bit.
  • 1ϕ→3ϕ converters, whether solid state or rotary, tend to have some losses, so if I put the transformer before the converter, I need one that’s oversized by about 50%.
  • With the converter-based options, I don’t need to mess with the motor wiring or the motor starter per se.

So… am I missing something? What do other people do to run 440V/3ϕ motors that cannot be rewired?

It seems that even if I manage to cobble this together from used parts, I’ll spend about as much on the power supply as on the tool. But given the price of the tool new and used, that might actually make sense, and besides, I’d end up with a source of 440V/3ϕ power allowing me to operate future craigslist acquisitions that nobody else wants because they come with such wacky motors…

5 replies so far

View crank49's profile


3917 posts in 2131 days

#1 posted 05-01-2013 06:33 PM

Today the industry standard is 480 volt 3 phase. Nominally this is the same as 440 or 460 volt.
Just like 110/115/120 volts are the same, or 220/230/240 volts are the same.

A VFD can be had that will take 115 volt, single phase input and output 230 volt 3 phase. I just never saw one that will output 460 volt 3 phase.

Assuming that is not available, the best option would be a transformer to go from 115 volt single phase to 460 volt single phase. Then use a standard VFD to convert the single phase to three phase.

You don’t want any disconnection between the VFD and the motor. They should be wired directly together.

-- Michael: Hillary has a long list of accomplishments, though most DAs would refer to them as felonies.

View srzsrz's profile


37 posts in 1027 days

#2 posted 05-01-2013 07:07 PM

crank49, that’s what I figured, but thanks for confirming!

View Loren's profile


7982 posts in 2808 days

#3 posted 05-01-2013 07:49 PM

Often on 3 phase motors (maybe always) there is a box on
the side. In it are typically 9 poles. At 220 volts 3 phase
the 3 input wires go one way (there are bridging wires
or plates that connect the other poles) and at 440 volts
the setup is different. These are “high voltage” and “low
voltage” setups.

There may be a diagram inside the box lid.


View crank49's profile


3917 posts in 2131 days

#4 posted 05-02-2013 04:04 AM

Rick, I’m real impressed that you bought over 9 VFDs over the years, But I have bought over $400,000 worth of them myself. I have designed all kinds of equipment from variable flow 200hp sand drying systems to 960KW heat treat furnaces to an 1800KW induction melting furnace that ran on VFDs. Nothing I or Loren said was a mistake or incorrect.

Upon looking at your home page I wonder why anyone would post on this forum for over 5 years and make a comment like “Lumberjocks is the worst wood forum I’ve ever seen…” Just saying.

-- Michael: Hillary has a long list of accomplishments, though most DAs would refer to them as felonies.

View srzsrz's profile


37 posts in 1027 days

#5 posted 05-03-2013 03:33 AM

Rick, I’m not sure what you mean by “there is no way you can go from 120 to 440 volt with a VFD.” I understand that VFDs aren’t boost converters, and never suggested trying to use one as such. I also understand that transformers rated for stepping all the way up from 110V to 440V are uncommon, but they sure do exist, rated as far up as 10 kW. They are probably more expensive than 220 to 440 transformers, but once you have transformed the power up to 440V, I’m having trouble seeing how a VFD could even tell, let alone care, whether the 440V it’s presented with was transformed up from 110V or from 220V.

Loren, thanks for the info! I know the setup you describe is very common, especially on NEMA-style motors, but I’m pretty sure that it does not apply to this particular motor, which as I said has Dahlander windings intended to be wired as YY or Δ, resulting in two different speeds at the same voltage. The forum post I linked to is really the best explanation I have been able to find of that type of motor.

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