Cliff;
A few comments here. Depending upon your local automation supplier or motor shop you may end up paying way to much. Especially if you walk in not knowing what you want. In a nut shell they see you coming and realize they will have a lot of work to do to seal the sale.
So if you can't find a local dealer willing to do the engineering for you you need to do the engineering yourself. The first thing to do is to find out how the lathes where normally motored. The idea is to find out if the 3HP is really needed, what class motor RPM is normal for the lathe and what frame sizes will easily fit the machine. Once you know what motor will go in there you can then start shopping around.
You might try automation direct @ www.automationdirect.com to get an idea of motor costs for new. Be sure to look at both the inverter rated and the non inverter rated motors. Only you will know how you expect to use the lathe and the value of going to an inverter rated motor. You can spend anywhere from $200 to $500 for a suitable motor new (plus shipping and extras).
That is still a lot of money so the next suggestion is to check out www.surpluscenter.com. They have a range of suitable motors from about $90 up to a couple of hundred.
If that doesn't work you might want to check with your local farm supply houses. While they often carry only single phase they may have three phase motors on hand. Junked machine tools / junk yards / surplus houses are another good place to find motors.
In the end you should be able find a good motor for a reasonable price.
Buying a three phase drive to run off of single phase is a bit more work. Once you have a motor and running conditions you should be able to run the info through their work sheets and come up with a suitable drive. Every manufacture will have the technical info available to size a drive for you, you should be able to find a number of online sources.
As far as a transformer on the output side of the drive that is a no go. Transformers don't work well outside their operating frequency. They also don't like square waves and harmonics. What you could do is to use a setup transformer to drive a three phase 575 volt drive. Depending upon your success in finding a transformer at a reasonable price you would then have to find a drive that can handle single phase input at that frequency. Generally the single phase limitation is due to the front end rectifiers and their current handling capability. So that would send you back to talking to an applications engineer. In the end you may find yourself running a much larger drive just so it can safely handle the input currents.
In the end it might be cheaper to go with a new motor and drive. With careful shopping you should get the motor and drive for less than $500. Go to a two horse power implementation and you might shave a hundred or more off that.
Be aware of a few things though. Some of the cheaper drives assume mounting in a control panel. A drive suitable for mounting without a control panel will cost more. You may also end up needing line reactors and other misc. components.
If this all sounds like a lot of info, it is if you haven't done an upgrade like this in the past. It isn't exactly complex though, it is more a question of getting your facts right and using that info to shop for a motor and then a drive.
There are plenty of people on the forums familiar with the various approaches. Some guys like to go the DC motor route as even new controls from your local automation house are cheap. Surplus DC motors in the right size are fairly easy to find too.
If you really wanted to you could throw a single phase motor on there. Honestly though this would be my last resort.
David A Frantz
websterindustro@mac.com
Sent from my iPhone.
On Sep 10, 2010, at 12:58 AM, cwswan <cwswan@wildroseinternet.ca> wrote:
> Any ideas on where to get a transformer that will give me 575Volts? I
> spent most of the day talking to electric motor suppliers and rewinders
> in Edmonton but got nowhere. They all want me to spend thousands on
> inverters or say it cant be done. I looked at the Hitachi site and
> their units seem to have the same voltage output as their input. It
> looks like i need a 220V single phase to 240V 3-phase inverter then a
> 3-phase stepup transformer to get 575V-3phase from the 240V -3 phase.
> Anybody know of a supplier? Thanks for the replys so far and in advance
> for any further help.
> Cliff Swan
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