Getting three phase 415v from single phase 480v?

Thread Starter

yachtwork

Joined Dec 19, 2019
5
Hello all- I am trying to run a three-phase motor from a single-phase power source. Currently, I have two leads coming from a power box. Each power lead is 240v when I test hot to neutral. When I test from one hot of one power lead to the second hot of the second power lead I get 480v. When I look up at the pole transformer I see two only two wires coming out of it connected to my power box. Does this mean I have two-phase power at 480v with a center neutral? Anyway, I am trying to run a 415v three-phase motor (on a lathe). My thought is to try and get three-phase from single-phase, maybe using a couple of capacitors to make three-phase. I don't need a lot of power from the motor so I am not worried that I will overload the line. I would just put a single phase motor on the lathe but it has a cooling pump that is also three-phase and I would like to keep the system original. Does anybody have any thoughts on how I might be able to make this work? Thanks.
 

Thread Starter

yachtwork

Joined Dec 19, 2019
5
One more question- The motor is three-phase 415v. I happen to have a single-phase to three-phase 240v VFD converter. I am guessing I can't run the three-phase 415v motor on three-phase 240v? Maybe someone has an idea on that?
 

MisterBill2

Joined Jan 23, 2018
4,847
Some motors have dual voltage windings and can be wired for either a high or low voltage. And yes, you can run the 480 volt motor from 240 volts, but the power will be lower. AND you can use one of the lines and the neutral to power that 240 volt VFD, it may be all set for 240 and neutral power.
 

MaxHeadRoom

Joined Jul 18, 2013
19,685
You cannot run a 3ph motor off of 1ph unless you set it up as a RPC (rotary Phase Convertor), the other preferred method is single phase into a VFD, to obtain 3phase out.
Where are you located that you have 480 single phase?
Max.
 

Thread Starter

yachtwork

Joined Dec 19, 2019
5
You cannot run a 3ph motor off of 1ph unless you set it up as a RPC (rotary Phase Convertor), the other preferred method is single phase into a VFD, to obtain 3phase out.
Where are you located that you have 480 single phase?
Max.
Thanks. I'm getting a lot of good ideas here. I'm new in New Zealand where I'm told we have a MEN system. I think that is multiple earths to neutral. I sent over a bunch of equipment I bought in the states and am trying to get that to work on the NZ 50Htz/240v system. The lathe I am working on I bought here. To be honest 480v seems like a lot of voltage for me to be playing with. I have a few options trying to get this lathe to function. I can just put a single phase 3hp cap start cap run motor on it and not use too much power. Or I can buy a small protable genset that is three phase 400v but I don't think I'll use the lathe that much. Or I can figure a way to power it from my two phases I have coming to the shop. No solution has popped up as the easy answer yet.
 

MisterBill2

Joined Jan 23, 2018
4,847
One more question- The motor is three-phase 415v. I happen to have a single-phase to three-phase 240v VFD converter. I am guessing I can't run the three-phase 415v motor on three-phase 240v? Maybe someone has an idea on that?
With that VFD converter, if it is able to use a single phase supply and provide the 3 phase output, you may be all set. Some VFDs rectify the source power to DC and then use a 3-phase inverter to provide the output. So it all depends on what that converter is. So now you can investigate that.
 

MaxHeadRoom

Joined Jul 18, 2013
19,685
I thought that Australia & New Zealand had a similar supply as the UK.
i.e. Residential supply is from one phase of a 3ph star neutral connected transformer. 230/240 and 400v phase to phase.
Not sure why you appear to have 2 phases, but if the same as UK applies,the other phase should be available?
If you only have the 2 phases, which alone is equivalent to single phase; you could feed into a VFD and obtain the 3ph for the motor.
However, it may pay to just use a 240v 1ph VFD and purchase the correct 230v motor.
Max.
 

dendad

Joined Feb 20, 2016
3,253
If you had 2 phases of 240V, measuring between them will give you 415V. As the measured voltage is 480V, you have only one phase. It sounds like you are being fed from a center tapped single phase transformer.
As mentioned above a couple of times, buy a VFD to drive your motor of the 240V single phase.

I do not know how good these are but, search Eabay for "3HP VFD" and you will get a stack of hits.
 

Thread Starter

yachtwork

Joined Dec 19, 2019
5
Thanks for all the help. A lot to consider. I am going to go take a better look at my VFD sitting out there and ponder the ease of each solution. Thanks again for all the help and ideas.
 
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