Herbert 4 Senior Pre-optive Lathe Problem

According to George :

Hmm ... you are operating it from a "static phase converter" such as those made by Phase-o-Matic? If the pre-op motor is a single phase motor, it (and the various control relays) will be sensitive to which two of the three phases they receive power from. They must be powered from the two wires which go through to the 220V single phase line, as those are the only two which are sure to have power.

I'm presuming that you had the converter stored separately, and had to re-connect the lathe to the converter. What I would suggest is that you disconnect the three phases from the converter (or from the plug, if you have set it to plug into the converter, but that would probably not have changed the wiring), connect each wire to the terminal to which the next one was connected, and try again. If that doesn't fix it, try the same change again once more.

Yes -- there is a more analytic way to do this, but since you say that you don't have the manual for the machine, this should be easier.

Hmm ... another consideration -- the start capacitor in the phase converter may have died while it was in storage.

If you're using a rotary converter, or a VFD, then things should be simpler.

I must admit to never having even *heard* of this brand of lathe, and I'm not quite sure what a "pre-optive" motor does. My guess is that it may adjust the variable speed pulleys.

I'm willing to bet that there is nothing wrong with the lathe (other than a few blown fuses), and that the problem is either with your phase converter, or with its connection to the lathe.

You have my suggestions above.

Good Luck, DoN.

In spite of not knowing my lathe you may have hit it on the head. I did change the wiring from the 3 phase converter. I used it for a pillar drill and the phase rotation was wrong so after checking that it was correct rotation for the lathe I did not check which one was the "dead phase, It only come up to voltage when the motor load comes on and although the pre-optive motor is 3 phase it is very small and not enough load on the converter, I feel.

The preoptive motor allows on-the-move speed changes to be selected prior to requiring the change - at which time you just press a button and it changes , rather like using an epicyclic gearbox on a car. Herbert is very well known in UK and there are a lot still about. Mine is far too big and complicated for what I do with it, but it is better to have a lot of facilities and not use them than not having enough and always getting stuck.

Thanks very much. I shall try your advice tomorrow, or Friday as I shall be busy tommorrow morning. Regards George.

According to George :

I don't know your lathe -- but I know things which can be in common between quite a few lathes, and this appeared to be something which could appply here.

You might want to make a rotary converter, then. That would have no problem running a smaller three-phase motor. Since your lathe already has an excellent way to change speeds (from the part below), there is little reason to use a VFD for this -- and the extra controls in this lathe might well make a VFD more difficult to apply.

If you can scrounge up a larger three-phase motor to use as an idler -- one at least 50% higher horsepower than the lathe's own motor, you should have no problems using the preoptive motor as well. You can even use the existing phase converter as a starter for the rotary phase convertor's idler.

And -- the spindle motor can act as a rotary converter to run the smaller one. If the speed control on the spindle is the typical variable-speed pulley, those are not supposed to be adjusted except when the main motor is running, so this should not be a problem, once you can get the spindle motor spinning.

That sounds like a particularly nice lathe -- and well worth putting it back into service.

O.K. Best of luck, DoN.

Hi Don,

It's running again. I could not wait till tomorrow. There were a number of things wrong, the main one being the "dead" phase being on the wrong wire. I changed it once and the light over the chuck would not come on and when I changed it again, although the pre-op motor was still jamming, I tried the "inch" button, while the pre-op was running and even though it did not start the main motor - there was a hefty click as it tried. Next I went back to the chuck speed selector knob and button and, working on the theory that, as it had freed up once, it was a simple jam caused by non use and / or damp, I tapped the external controls lightly with a small hammer for a while. The next time I tried it, the jam was overcome and although the main motor was trying, it was not able to start up due to insufficient current from the converter. The converter has various switch positions which you are suppose to adjust for lowest current when the 3 phase device is running. I tried a few other positions and got a quicker trip out of the pre-op motor but a more healthy attempt by the main motor (3 / 7.5 Hp.) to start. I tried this a few times and finally I got the main motor turning before the pre-op tripped and everything got dramatically better after this. With a proper load on it the converter gives quite a good 3 phase supply.

It must have all been very stiff and when it started the oil gradually got back in the works. I left it running and went up and down the gearbox several times and everything was fine. There do seem to be several oil filling caps around the machine, but I am reluctant to pour anything in until someone can tell me what sort of oil I should be using. When it had been running for a minute or so it sounded very smooth and no vibration, so there is not much wrong with it. I got on with some painting and left it running light for about an hour. It got nicely warm and I am sure that I will not have any problems in that area.

Thanks to you, I am back in business.

Best regards George.

According to George :

Great!

O.K. That is a bit better than some versions, as it offers a way to tune out the "imaginary" current.

Actually -- what is probably giving you a three-phase supply is your spindle motor,acting as an idler once it is started. "static" converters, such as yours appears to be, simply observe the third phase, and as long as it is below a certain value, keep a starter capacitor switched into the circuit. This will work properly only on a fairly narrow range of motor horsepowers. If your pre-op motor was starting, this makes me suspect that it is a single-phase motor, not really a three-phase one.

As long as the spindle motor is running, it generates the third phase for anything else which might need it. However, if you want three phase good enough so the whole system works normally, what I would suggest is that you get an old three phase motor, perhaps around 10 HP, and use the static converter to start it. When it is running, it will be generating the third phase for you, and your lathe should be fully happy -- even if the pre-op motor *is* three phase. Just mount it somewhere out of the way, use the static converter to start it, and you now have a rotary converter in your shop -- ready to feed three phase to any tool of the 7.5 HP or lower range. (This presumes that you have enough current to start the 10HP motor in the first place.) You probably should make some kind of housing around the shaft so nothing gets fouled in it while it is turning.

Great!

Best of luck, DoN.