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220 To 440v 3phase Minimum 2kva Transformer


Active User
H-M Supporter-Premium
When my Van Norman 6 arrived several years ago she had a 1725rpm, 1phase motor.
That wasn't right for all kinds of reasons.
I was gifted a tired 3/4hp, 1140 rpm, 203 frame motor. That worked for a while but was getting hot and smokey.
As this is a "no smoking" shop, I began the search for the correct motor.
Scored an OEM 1140rpm, 1hp, 204frame motor. Freight cost more than the motor. Yep, looks the same as the ones in the VN parts manual and brochures. However, there were no guarantees about condition other than the shaft spun freely.
When she arrived I was suspicious when she only had three wires coming out. But seemed to work well.
Then I noticed I was having significant power problems at higher speeds.

One of our local HM members is adept at 3phase he visited this past Thursday.
He opened my 20hp RPC, and ran some clamp meter tests and pronounced as healthy. As well as my home wiring job as adequately safe (not necessarily code).
When he opened up the motor, he identified that like the bearings the windings appeared new.
However, when she was rewired she was wound as 440v only.

My options.:
1) use at low speeds only.
2) rewind the motor.
3) find someone who is willing & able to possibly identify, cut, tap in additional wires to make her convertible to 220v (this may not be a real option).
4) find a 220v-440v 3ph minimum 2kva transformer.

Am trying to logically work through the options.
If any of you electrical gurus has an appropriate transformer which you are tripping over, then I'd rather purchase from you, than off eBay/other. I'm willing to pay fair market value.
Starting next week I'll check the local used motor shops to learn if they've got a used one on the shelf.

Thank you!!

British Steel

Active User
Active Member
Hi Daryl,

if the motor's wound in star for 440v (only 3 connections, no links in the connections box) it *should* be possible to find the star point and bring each "other end" of the windings out to rewire in delta for 240v, not for the faint-hearted though! This is your Option 3, and may be the easiest / least expensive fix?

I've had success with a 400+ volt 3-phase VFD hacked to provide power for my (415v-only, difficult) lathe motor, funnily enough used 400+ volt, 3-phase input VFDs seem to go for far less than 240v single-phase, unbelievably less than 240 to 400v VFDs (which are basically the 3-phase 400+ VFDs with exactly the same hack, for which the vendors charge around £800 (in the UK)/ $1000 when it's just moving a wire or two). In my application I used an elderly ABB 3-phase 400+ volt inverter, and in view of the hack derated it from 5 HP to 3 HP (for that is what my lathe requires) - it was a matter of moving ONE wire (to a brass bolt I had to put through the PCB) and putting a link in to feed AC to twwo of the 3-phase inputs - it puts additional strain on the VFD's bus capacitors, but they're replaceable when they have had enough :)

Another approach is a 240-110v "site transformer" (used on building sites to reduce voltage to "safe" levels) as a boost transformer, which will give you around 350v - but these tend to be single phase... Three of 'em might be an expensive way to go!

Dave H. (the other one)


Active User
H-M Supporter-Premium
British Steel,
I truly appreciate your words of encouragement. The thought of keeping this 220-240v would be my choice. I really didn't have much hope that it was even possible.

Thank you,

Ulma Doctor

Infinitely Curious
Active Member
Hi Daryl,
you can run a transformer like this in reverse to get 440 from 240.
you would connect the output from your RPC (240v-3 phase) to the output(secondary) of the transformer.
the primary voltage wold then be connected to the 3 phase motor
the transformer would steal a little power in the process.
at HGR they have transformers of all kinds.
here is a transformer that would work, albeit overkill.
HGR#Inventory Number 0616-175-0044
you may be able to find a similar transformer there or elsewhere with different KVA ratings to suit your needs, i'd over rate the transformer somewhere around 25% to be safe.
(ie, if you need 1kva get a transformer rated for 1.25 kva and so on)
Last edited:


Active User
H-M Supporter-Premium
Thanks for thinking about HGR! There are some serious markdowns available and they've got some 3ph.
I've identified two used motor shops with presumed large inventories. I'm planning on checking in with them on Monday.
One of the places doesn't track inventory, they point you in a direction and you dig. This place therefore sells cheap.
Timing depends on the incoming snow storm, rumor is that we are going to have weather realted fun.

Thank you,


Registered Member
Hi Daryl,
my $.02,
a 3 phase 20hp motor < from your post>(correct me if wrong). so 20hp =27Amps or around 22kW at 460-480V.
however if it is a 1hp that looks like you could get a 2kW transformer, like you mentioned. could do this with buck /boosts but the interconnection is a lot easier if you get the 3phase unit. do you have 240V 3phase at your house? and is it 'Y' connected or 'wild leg delta', (center tapped so phase 'B' is higher than 120V).


Active User
H-M Supporter-Premium
I sincerely appreciate your .02!
do you have 240V 3phase at your house? and is it 'Y' connected or 'wild leg delta', (center tapped so phase 'B' is higher than 120V).
I'm completely lost on how to best answer your question.
However, since I made this original post I've been privileged to have more conversations with one of our quiet MN HM members (retired 3ph electrician). He's opened the covers of my RPC and stated he was impressed with how it is wired up (was commercially used).

Additionally, I've since followed up with one of his suppliers here in MN. They found a used 3kva 3phase 220-440v, they sold me at far below anything I'd seen used online. We are attempting to schedule an opportunity wherein he can help me with a safe install and teach me more stuff in the process.

Thanks for the input!!