The Shop > Tools
phase convertor
DavidA:
Just adding a bit.
The capacitors arrived today (RS overnight post, free)
It was too cold to bother much in the shed today, but I had to just have one 'play'.
I fitted the 10 MFD capacitor.
The motor hesitated briefly then spun up to speed.
The voltages at the motor connection block were
U1 - V1 399 Volt
V1 - W1 445 Volt
W1 - U1 419 Volt
And the currents
U1 0.85 Amp
V1 1.35 Amp
W1 2.42 Amp
Lot's more test to be done yet; both on and off load.
By the way, its a Star connected motor.
Dave.
DavidA:
Another update.
I now have the motor I acquired connected up as an idler and find it starts easily with 30 MFD attached. This now feeds my lathe via an isolator switch.
As mentioned before, I did decide that the DC injection braking was only a complication, so spent some time in the shed bypassing all that and have finished up with just the basic control panel, I.E forward, backward and stop.
At the moment I am having a bit of a problem with the contactor controls. I have a fairly good idea of where the problem lay.
Basically the lathe won't start up when I press the go buttons. But if I push in either contactor manually then it runs, but stops as soon as I release. So my contactor solenoids are not powering up. Tomorrow will be a 'having fun with my test meter' kind of day.
This raises a point for anyone else who may go the same route and use the book.
It gives you very good circuit diagrams , but nothing on connecting up the interlocking switches when you have two contactors. One for forward and one for reverse. Your on your own with that one.
I suppose that if you were really desperate to get running you could just use one contactor (with overloads) and place a manual change over switch between the overloads and the motor to swap two phases. Thereby getting your reverse.
Dave.
DavidA:
'It lives, Igor. It lives,'
I took the desperation route and set up the machine using just one contactor and no overloads.
But now I know it works (including the speed control) I can make everything neat and tidy. At the moment the pilot motor is held down to a table with G clamps and the lathe control panel is laying on a wooden chair with all it's innards exposed, Nothing has any covers on. (( need to get at the wiring to measure things). All rather dangerous :zap:. Re connecting the other contactor will give me a lathe that actually runs in reverse as well as forward.
I do believe my original problem was down to a disconnection in the contactor relay circuitry. Things quickly start to get complicated when the interlock switches are included.
But the pilot motor / capacitor idea works well. with the lathe running I am getting around 406 Volt average. A small tweak on the capacitance will probably improve that.
As the lathe is the biggest load I am likely to put on the system (and that draws less than 2 AMP), I'm quite satisfied. The only fly in the ointment is that as the transformer is fed from a 16 Amp trip in the house, sometimes the trip drops out on starting the pilot. No big deal as everything is fine once the pilot motor is running. Maybe an additional few MFDs just for starting will improve things.
I'll include some proper reading next time.
Dave :D
Andrew Wildman:
Dave, i changed my MCB to a c curve type rather than the standard b type as I had a similar problem with the transformer inrush current.
DavidA:
Andrew,
I'll probably do the same. It seems to happen only when it is cold.
An update.
I burnt a lot of midnight oil and managed to get the control panel wired up properly. So it now works as it should. Backward, forward and stop. Only the sud pump to sort out.
So, having got everything running I decided to do a quick test on the threading capabilities.
12 TPI would do.
Chucked up a bit of 1" steel bar. faced it off and took a light skim off the length. This is the first time the lathe has cut metal for three years.
Next, set up the gearbox. The 100/127 wheel set and it's banjo are still in a drawer, so the machine is still set up for Imperial.
I followed the instructions. Got to be careful with the Synchro as some operations are done with the machine running, and some are not.
So, spindle, is turning, leadscrew is turning. Close the half-nuts.
Nothing much seems to be happening. But wait, the saddle is moving toward the headstock, but very slowly.
Re check the gearbox settings. all ok.
A look at the reduction gears showed that someone has got then on all wrong. Instead of being a 1:1 gear train fron the spindle to the gear box it is reducing the ratio to 10:1 so I would be cutting something like 120 TPI.
And that is what it looks like.
Ho Hum. Never a dull moment.
Dave.
Navigation
[0] Message Index
[#] Next page
[*] Previous page
Go to full version