Lathe Help

"Bruce A. Frank" wrote in news: snipped-for-privacy@worldnet.att.net:

converter

Do you have a mulitmeter? This sounds like you have a dead short somewhere, or it is cross-phased. Take the multimeter, remove power from the lathe completely and ohm out the wiring, wire by wire in the motor circuit. Check for phase-phase shorting as well as phase-ground. Although you say the motor runs ok with no load, the insulation may be giving up the ghost on it. You may want to run it by an electrical shop that has a megger. This puts a substantial voltage load on the insulation to see if it is leaking down. I doubt they would charge much for testing it, since it is similar to hooking up a multimeter too it.

Thanks for the suggestion. What I have decided to do is scrap the wiring and build what I need from scratch with a drum switch for motor reversal and pulling a leg of the power for the accessories. I jumpered the motor directly from my rotating phase converter. It runs forward, then reverses when two wires in the supply are switched with the drum switch.

I would still like to f>

Bruce, to be honest, I think you are taking the proper approach. I deal with electrical machine problems..and frankly..some of the early Asian imports had serious deficencies in the electrical end. I think of them as Volvos. fairly decent hardware but the electrical sucks.

Im going out on a limb here and suggest as a final check before gutting the electical panel, to check the reversing relays. It sounds like one of the contactors is pulled in, or welded shut, and when you attempt to power it, its a dead short between contactor buses.

To simplify things even more..and make the machine even more versitile, I suggest investigating aquiring a VFD and remoting the forward/reverse/rpm controls to a small box on the head stock.

Gunner, who spent 3 hrs yesterday rewiring a customers Cadillac lathe after a nice long stringer got into the control panel.

The two highest achievements of the human mind are the twin concepts of "loyalty" and "duty." Whenever these twin concepts fall into disrepute -- get out of there fast! You may possibly save yourself, but it is too late to save that society. It is doomed. " Lazarus Long

Of course I have not seen the lathe, but I doubt if tracing out the system is as bad as you think it is. I would start at the motor and using a ohm meter find which relay connects to the motor. That would be either a reversing relay or the power on relay. That relay ought to connect to another relay which would also be either a reversing relay or power on. Should not be too hard to figure out which is the power relay as it would use only three contacts and would be a single pole relay. Then start at the power in and use your ohm meter to find where the power goes to first.

It is a pain to do it this way, but what if you get the original wiring diagram and someone has modified the wiring.

Dan

XXXXXXXXXXXXXXXXXXXXX Hey Frank,

Hmmmmmm... I don't think Anthony and I would be on the same page here. If you put in a new relay, and promptly blew the COIL on the new relay, then you either had a coil of the incorrect voltage, or you have bad auto-transformer or something, but the motor won't blow a coil, no matter what is wrong with it.

For me, a bit more explanation is required. What purpose has the coil that you decided was "blown", and how did you know the original was pppffffffuutttt? Is there any fusing in the control circuits?

Brand new drum switches are fairly expensive, at least three times the cost of the coil mentioned. If it was better to have a drum switch, it would have had it from the factory. They wouldn't go to all the trouble of designing and putting a row of switch gear in place if it wasn't required.

I can't exactly help you out though, but I do have a Taiwanese 13 X 40 lathe, with a 2-speed 3/1.5 Hp, 220VAC, 3 phase 60Hz main motor. But it only uses four relays........a potential (safety relay), one each forward and reverse which are interlocked, and one for the coolant pump. It uses a three-pole double throw centre off switch for the two-speed selection. It has a 100VA jumper selectable single phase control transformer to allow one of either 380, 440, 220 as the primary voltage. (The "380" isn't a common voltage to me, whereas 308 is, so maybe it is a translation or typo error on the draftsmans part....there is another place where he shows it as having a gRass fuse.)

Won't be this week, but if you send me your mailing address off list, I'll send you a photo-copy of my schematics.

Take care.

Brian Lawson, Bothwell, Ontario.

Brian Lawson wrote in news: snipped-for-privacy@4ax.com:

IF it was the coil that fried, I would agree, it's in the control circuit, however, he didn't say what fried, so I ASSumed it was the contacts from overcurrent.

As did I.

Gunner

The two highest achievements of the human mind are the twin concepts of "loyalty" and "duty." Whenever these twin concepts fall into disrepute -- get out of there fast! You may possibly save yourself, but it is too late to save that society. It is doomed. " Lazarus Long

The parts that burned are the contacts themselves inside the relay. I took the first one apart with visions of moving contacts around but found the burned ones were the largest contacts and they were badly melted. The voltage to the coils was just what it was suposed to be,

As for gutting this and starting over, I actually have a nicely built drum switch which I bought from Graingers for $37 a couple of weeks ago. Part of the problem with the relays is that the particular physical configuration is no longer manufactured. I had to special order the replacement, actually bought two, and it took a day or so to figure how to connect it...different number of connections.

When I was testing the motor directly a few days ago I used the drum switch and it did the job. My only hang up right now, and I haven't traced some of the wireing that runs under the gearbox area, is that there is a switch connected to a relay that is activated when you step on the treddle stop/brake...I would guess it cuts off the electricity and applies the friction brake at the same time. Making that remain functional will require more investigation.

Thanks for all of your help. Still would like t>

Thats easy. There should be a relay in there that is activated by the brake switch. It is likely normaly closed (brake switch) and keeps the relay engaged. That relay is supposed to feed the motor power to the forward/reverse relays. When you step on the brake, it opens the microswitch, drops the relay, which removes power from the motor. Wire this ahead of your drum switch. Ie between your incoming power (fused of course) and your drum switch. Unless you use a make/pic wiring order, the motor will start back up once you lift your foot off the brake, or turn off the drum switch..but many companies do just that. They expect you to be smart enough to turn off the motor after you step on the brake.

Gunner

The two highest achievements of the human mind are the twin concepts of "loyalty" and "duty." Whenever these twin concepts fall into disrepute -- get out of there fast! You may possibly save yourself, but it is too late to save that society. It is doomed. " Lazarus Long