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Old 16-01-18, 09:13 PM   #1
RobSmith
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Default 1ph to 3 ph converter working

Hi all.
My Colchester student lathe has been out of action for a year or so since moving house.
Going back some years to when I got it it had a Brooks 415v 3phase 3hp motor on it. It was great with this motor but the lathe was in a rented workshop 10 miles from the house. So I moved it to the house and installed a brand new (so not very heavy) single phase motor and meaty supply. This was the worst thing for the lathe. The vibration from the single phase "pulses" would affect the setting of the cross slide. I could never set it to a particular setting and be sure it would cut to what you would set it at. It would often take a thou or so more.
Since moving the lathe has been stached away in my mums garage. This has just got 13 amp sockets. After several popped fuses I decided that was a non starter.
I recently dug out a "drives direct" single to three phase inverter I bought at the same time I installed the single phase motor. The original three phase motor was just 415v and no other connections hence going for a new single phase motor and putting the inverter on the shelf when I worked out I had an unsuitable motor.
After a bit of ebaying I bought a suitable brooks motor wired 220v (delta) / 415v (star) with six terminals.
I borrowed a friends lathe to turn out the pulley bore and I broached the keyway to match the new motor.
The inverter is now lashed up on a bit of plywood bolted ti the back of the lathe. The original lever and switch are used to switch the converter into action and to switch off then actuate the brake when pressed down
It is now lovely. The soft start is realy nice, it is quiet again and accuracy has returned.
I think it is the way forwards if you have an old three phase machine and just a single phase supply
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Last edited by RobSmith; 16-01-18 at 09:16 PM.
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Old 16-01-18, 09:34 PM   #2
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If you're feeling adventurous you can sometimes dig out the star point on a 3 phase motor and split it to make a 6 terminal 220/415 volt motor.

Stuart.
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Old 16-01-18, 09:53 PM   #3
listerdiesel
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Our pillar drill at the factory has had a phase-changing capacitor on it since I brought it back from Holland in the 1970's.

It had Delta/Star connectivity and has run on single-phase ever since.

We have full three-phase at home, we had it put in back in 1986.

Peter
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Old 16-01-18, 09:56 PM   #4
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Quote:
Originally Posted by Robotstar5 View Post
If you're feeling adventurous you can sometimes dig out the star point on a 3 phase motor and split it to make a 6 terminal 220/415 volt motor.

Stuart.
I can't remember if it might have been 415v delta. At that time I decided it wasn't suitable and too much work to sort out. The single phase option seemed the simplest at the time. I still have the original motor.
We are building our own house and then workshop. I shall be setting up a 415v 3 phase (off grid) supply to run my other machines. I may reconfigure the lathe to be 415v again but I do like the soft start of the electronic drive
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Old 16-01-18, 09:58 PM   #5
RobSmith
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Quote:
Originally Posted by listerdiesel View Post
Our pillar drill at the factory has had a phase-changing capacitor on it since I brought it back from Holland in the 1970's.

It had Delta/Star connectivity and has run on single-phase ever since.

We have full three-phase at home, we had it put in back in 1986.

Peter
Is that running just 2 of its three phase windings then?
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Old 16-01-18, 10:05 PM   #6
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Quote:
Originally Posted by RobSmith View Post
I can't remember if it might have been 415v delta. At that time I decided it wasn't suitable and too much work to sort out. The single phase option seemed the simplest at the time. I still have the original motor.
We are building our own house and then workshop. I shall be setting up a 415v 3 phase (off grid) supply to run my other machines. I may reconfigure the lathe to be 415v again but I do like the soft start of the electronic drive
Plus you get much better speed control with a VFD

Stuart.
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