Having no three phase supply, I recently decided to convert a large pillar drill I acquired a few years ago, from three phase to single phase power. First of all, I went to a local motor rewind specialist and asked if they could convert the existing motor. They said they could but it would be altogether better to just put in a brand new single phase 1hp motor; a four pole motor giving the correct 1500 RPM. I have now fitted this motor and the machine is excellent. - the single phase supply has enough capacity to cope with the load.
My question is this: can this approach be used on other machine tools; lathes and milling machines? Have I just spent too many years being put off larger machine tools by the installation of three phase power, or an inverter? Are there any disadvantages to using single phase: less smooth power delivery or lack of torque?
OK, I realise this is three questions but any advice about the maximum size of machine I could consider running on single phase power would be appreciated.
I also have one VFD/inverter shared by my lathe and my drill press. I recently put 3-phase motors on both machines.
The drill press is fabulous.
I use only one VDF for both my lathe and my drillpress. Just Plug in and plug out in one female connector.
Not being that educated on the Variable Frequency Drive method, I opted for the Rotary Phase Converter route. It has worked many years so I should not complain. I used a design and schematic I found on the Net that uses a push buttons set up to start and stop the idler motor. Chasing used parts on the network and a used idler motor, I ended up with around $300.00 in the project. One advantage the RPC system has is that I could tie all my three phase machines to it. Of course I only run one machine at a time to not overload the RPC circuit breaker.
I would not go this route again after helping friends install VFD systems. The RPC does not give me variable speed and the cost of the import VFD systems for 1 to 3 horse power motors is now in the same price range. Only draw back is that you would need a VFD system per machine.
Regarding maximum motor size, There is no three phase available near me. I am running a 15HP air compressor and a 20 HP lathe on single phase power. This is using a RPC and transformer to get home made 480 VAC 3 ph.
There are several options available. 1) replace the three phase motor with a single phase motor. 2) build or buy a RPC (rotary phase converter) for your shop that can run several machines. 3) purchase a VFD (variable frequency drive) for your machine.
#3 is fast becoming a very cost effective solution. VFD's are quite inexpensive and will take single phase input and output three phase. Additionally, you get a variable speed drive.