Rotary Phase Converter a Different perspective.

[Ark1]

First off I am an electrician located in Ontario Canada. Started my apprenticeship in 1975 at the Nanticoke Generating Station then owned by Ontario Hydro. I moved on into High Voltage transformer distribution Grid work, then on to Construction of buildings and renovations of commerical and industrial nature.

About 15 years ago I purchased a Tos FN20 Milling machine with NST 40 taper. Not a big machine but it has a lot of versitality.( Tos was not sold in the USA because it was built in a communitist country.) The machine new in 1977 was $27K and it weighed 2200 LBS. 2 HP on the spindle, 2.5 HP on the power feed for all 3 Axis and .2HP for the coolant pump. All 600 Volts and 3 phase. I purchased the machine for $1700, it came with a vise and a 70 LBS dividing head with #4 taper and chuck. So now came the issue of how to run this machine as I only have single phase power at my home. I looked at drawings and books and even found a used Roto Phase 208/ 3 phase unit for $600 but I needed a 600 volt unit, word was they don't make it. I wondered why. So I set out to build a 240 volt single phase to 600 volt 3 phase unit.

I knew the theory and applied it. Because I am in the trade I knew where to look for used parts and built it for $300 CND.

Those that have been around Phase converters and motors know that once you get a 3 phase motor up to speed a phase can be lost and the motor will still run. What you will not know is what direction it will turn the next time you start it. To get around the self starting problem of shifting phases with capacitors I made it simple. I used a 1/4 HP motor with a 6" pulley connected to the shaft of the 5 HP 600 volt 3 phase motor sitting on the floor. The 5 HP motor has a 5" pulley on it. The 1/4HP motor runs the 5 HP motor up to a speed that is faster than sycnronous. 4 seconds latter a timer drops out the 1/4 HP motor and energizes a contactor that applies 240 volts across a single phase transformer rated at 240/600 volts. The 600 volts is applied to the 5 HP motor that now locks into sync and generates the Phantom phase. Capacitors from parking lot lights are used to shift the phase voltage. I used a volt meter to do this and a few start and stop tries with the motors on the Tos 20. I have never had any of the mill motors stall out when using this phase converter.

The 1/4HP motor idles and adds rotating mass when starting the spindle drive.

The wiring is rough but was a quick way for me to prove my ideal, it worked 15 years ago and I have never gone back to clean it up.

The big frame 5 HP and 1/4 motor was purchased from a Demoliton Yard for $50, the cabinet and transformer from a Used Electrical supplier for $250.

If any one would like an electrical drawing, I could do one, line scan and post.

Ark1.

[racear*2865]

yes, I would like to see the dwg.
thanks
racear

[Ark1]

Not complicated and it works very well.


TonyK.

[Knick]

I have a question

I have never checked to see but are you saying that depending on what direction the idler spins at start up, it will effect what direction the motor that is being driven spins?
Hope this makes sense

Thanks

Originally Posted by Ark1 First off I am an electrician located in Ontario Canada. Started my apprenticeship in 1975 at the Nanticoke Generating Station then owned by Ontario Hydro. I moved on into High Voltage transformer distribution Grid work, then on to Construction of buildings and renovations of commerical and industrial nature. About 15 years ago I purchased a Tos FN20 Milling machine with NST 40 taper. Not a big machine but it has a lot of versitality.( Tos was not sold in the USA because it was built in a communitist country.) The machine new in 1977 was $27K and it weighed 2200 LBS. 2 HP on the spindle, 2.5 HP on the power feed for all 3 Axis and .2HP for the coolant pump. All 600 Volts and 3 phase. I purchased the machine for $1700, it came with a vise and a 70 LBS dividing head with #4 taper and chuck. So now came the issue of how to run this machine as I only have single phase power at my home. I looked at drawings and books and even found a used Roto Phase 208/ 3 phase unit for $600 but I needed a 600 volt unit, word was they don't make it. I wondered why. So I set out to build a 240 volt single phase to 600 volt 3 phase unit. I knew the theory and applied it. Because I am in the trade I knew where to look for used parts and built it for $300 CND. Those that have been around Phase converters and motors know that once you get a 3 phase motor up to speed a phase can be lost and the motor will still run. What you will not know is what direction it will turn the next time you start it. To get around the self starting problem of shifting phases with capacitors I made it simple. I used a 1/4 HP motor with a 6" pulley connected to the shaft of the 5 HP 600 volt 3 phase motor sitting on the floor. The 5 HP motor has a 5" pulley on it. The 1/4HP motor runs the 5 HP motor up to a speed that is faster than sycnronous. 4 seconds latter a timer drops out the 1/4 HP motor and energizes a contactor that applies 240 volts across a single phase transformer rated at 240/600 volts. The 600 volts is applied to the 5 HP motor that now locks into sync and generates the Phantom phase. Capacitors from parking lot lights are used to shift the phase voltage. I used a volt meter to do this and a few start and stop tries with the motors on the Tos 20. I have never had any of the mill motors stall out when using this phase converter. The 1/4HP motor idles and adds rotating mass when starting the spindle drive. The wiring is rough but was a quick way for me to prove my ideal, it worked 15 years ago and I have never gone back to clean it up. The big frame 5 HP and 1/4 motor was purchased from a Demoliton Yard for $50, the cabinet and transformer from a Used Electrical supplier for $250. If any one would like an electrical drawing, I could do one, line scan and post. Ark1.

[Ark1]

The idler motor is connected by a belt but direction is not really relevant. Output rotation will always be the same and rolling a phase to obtain the correct rotation is all that is required. Once the start timer has timed out 600 Volts in my case, is applied accross the terminals of 1 phase of the 600 volt motor. Since the run up/ idler motor brings the phase converter past Sycnronous speed when current is applied the phase convert motor locks into sycn and now drives the run up/ idler motor that gives more rotation mass by the connected belt.

Please note I am responding to my Phase converter that I built in the above statement.

Commercial units that self start, can start in the opposite direction should a capacitor go open on one of the phases. Although turning and producing a phantom phase the rotation would now be reversed that is feeding into your machine, thus running it backwards. If the phase shift on a self start motor phase convert is small there runs the risk of it starting in a different direction each time it is started.

TonyK.

[Al_The_Man]

Originally Posted by Ark1 Commercial units that self start, can start in the opposite direction should a capacitor go open on one of the phases. TonyK.

Not if it uses one start capacitor from either of the 240v 1ph via a P.B. or timer.
I built this one from Fitch Williams design that includes tuning.
http://metalworking.com/dropbox/_1998_retired_files/
Look for FRW files.
The run capacitors are used mainly to improve the power factor.
Al.

[Knick]

Originally Posted by Al_The_Man Not if it uses one start capacitor from either of the 240v 1ph via a P.B. or timer. I built this one from Fitch Williams design that includes tuning. http://metalworking.com/dropbox/_1998_retired_files/ Look for FRW files. The run capacitors are used mainly to improve the power factor. Al.

Al

I have several start caps on a timer. I have never checked to see if my idler
always starts in the same direction. So if I understand correctly as long as everything stays the same (all caps in working order) idler will start in same direction. I am still in the stage of putting things together and getting ready to fine tune the run caps. I am trying some different things as my air compressor is a duplex unit and makes tuning harder as load changes are all across the board. last thing I want is the compressor pumps running backwards as they still pump this way and Im sure I would never notice. Im glad I read this, Thanks guys

[Al_The_Man]

The start direction is decided on which 240v leg it is fed from.
It is only in circuit very briefly.
Al.