Clausing magnetic switch won't latch


I bought a 5914 Clausing lathe last weekend. I"m running it off of a
rotary phase converter, that at this point does not have balancing
capacitors.
The drum switch on the lathe has a set of momentary contacts inside
that activate the magnetic switch when you move the handle a little
past the forward or reverse position. When the momentary contacts are
closed, the switch pulls up and the motor runs, but the mag switch
drops out as soon as the momentary contacts are released.
I have tried exchanging the different leads from the RPC to the lathe
so that the wild leg wouldn't be part of the mag switch circuit and
that didn't solve the problem.
The wiring inside the drum switch was not standard, and connecting the
power lines to the places it had been when previously, it didn't run.
Same symptom - switch would pull up ,but not latch and motor ran with
a pulsation / vibration. I got the wiring diagram from Clausing and
rewired it to factory standard. Still won't latch. Using the drum
switch and bypassing the mag switch works fine. The motor itself
seems to be OK.
What I can see from the wiring diagram supplied by Clausing and from
the diagram inside the mag switch box, it appears that all is wired
correctly. I am having difficulty following the flow of power in the
switch. The diagram has me confused.
Any thoughts on trouble shooting?
RWL
Reply to
GeoLane at PTD dot NET
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Contactors need an extra NO ancillary switch ("latch switch") which bridges across the momentary start switch, keeping the relay coil energized. A momentary stop switch is then in series this switch/coil.
If there were a 4th pole on the relay, this could be used, also.
This latch switch could be bad, or just not wired in. I've seen these switches go bad. Or, the mechanical connection of this switch to the relay is loose, so it is not "making". Sometimes the switch itself is loose, as these switches can be often be added on, taken off, etc.
Reply to
Existential Angst
Please do balance yer rpc! I burnt out a lot of shit with that goddamm wild leg!!
It's actually perty simple to do, much simpler than many of diy sites (and std web refs) recommended here make it out to be -- imho. Altho some of those setups are indeed enviable...
I did a very complicated multi-motor (staged) and switchable multi-capacitor system, whose magnitude of pita factor (and expense) I didn't really grok until my buddy asked me to build one for him.... holy shit.....
So out of desperation, I did nearly as good a system for him, with *much* greater simplicity.
First, these asshole rpc mfr's put starting caps that are way too large, which further bumps up the voltage of the wild (generated) leg. You can proly cut that down those caps by half to 1/3 -- which immediately improves the V of the wild leg -- and which means if multiple caps were used, you can use the extra caps to balance the rpc.
If line V is L1L2, and the starting caps were on L1L3, you add the balance to L2L3. Except put a switch (S2) in the caps between L2L3.
How much capacitance to start the rpc? Whatever "sounds" reasonable. You don't need the motor to instantly get up to speed (as these effing rpc mfr's seem to think is so important), but you don't want it to take 10 secs, either. About 1 sec seems OK.
I've forgotten exact values, but I seem to remember about 100 uF to start, 60-80 to balance. Season to taste. If you have a good ear, you'll notice that the right balance of caps (tightest V) results in the lowest hum/buzz of the motor.
So now, to start the rpc, make sure S2 is off, and start the rpc as normal. Then, just flip S2. Wahlah.... Iow, the reduced value starting caps also stay in as balancing caps, and are always active. The other balancing caps are switched in only after the motor is running.
Using this method, my buddy's rpc measured (the other day) 241, 242, 246 -- not bad, eh? Mine is even tighter -- on the order of 241,243,245, on a good day -- but with just too much effing electrical drama.
You'll get proly 100 other opinions, and altho ahm no 'spert, I grappled with this for a long time, and bought $200 worth of caps from Graingers at 1/3-1/2 price, and did some amount of experimenting. I don't think it gets much simpler or cheaper than my buddy's system, and the voltage speaks for itself.
Just remember to flip in S2!!! Which, on my system, I sometimes forget to do!!! goodgawd....
If you want to go "cap wild", you can have two banks of caps, ranging from 100 uF down to 10 or 20 caps, with a switch for each cap. One bank gets switched across legs L1-L3, the other bank across L2-L3.
Thus, depending on what rpc idler you plan on firing up, you can choose your starting caps, and then switch those in/out, and the other balancing caps in, as needed. You can have 3 cheap digital VOMS attached, for on-the-spot balancing.
This is easier described than done, and is really a wiring pita, altho it's not rocket science either. I used regular 49c wall switches, screwed to wood, with zip cord. Altho my set up is not as nicely done/automated as some diy setups you'll find, it is the most versatile and "tune-able" that I've seen anywhere on the web.
Bear in mind that a bunch of small 3 ph motors pack as much oomph as one big honking idler, a point much de-emphasized in rpc discussions. This way, you just need starting caps for the 1st idler, which will start up subsequent idlers, which can then be balanced with switchable caps, to taste.
I breakered my wild leg(s) separately, fwiw. Too much effing drama, tho.
Reply to
Existential Angst
A quick/dirty "fix" to this is to put a simple HD light switch in parallel with the momentary on switch. The problem is then, the Off momentary will not work; you'll have to switch off the light switch to turn off the motor. Which is not a big biggie, imo.
But you should be able to find the defective or mis-wired latch switch sooner or later.
Reply to
Existential Angst
[ ... ]
You've done quite a bit of the right troubleshooting, but one thing comes to mind as a possibility. The switch probably has overheat coils which trip a set of contacts open when too much current is drawn through them. These interrupt the current to the contactor (relay) coil, thus dropping it out and stopping the motor.
The momentary contact apparently bridges over both the heat switches, so it engages the relay coil -- until you release the momentary contact.
There is probably a ratchet to reset the heat coils -- there will be at least two, and perhaps a full three, though two is all you really need.
If the motor was originally wired for 240 VAC and it has been rewired for 120 VAD, the current the motor draws will have doubled, so you need a new set of heat coils rated for the new current.
Of course -- it could be something else -- but this is what I would check first.
Good Luck, DoN.
Reply to
DoN. Nichols
You just described how these Clausings are wired. The NO contactor is the 4th terminal in the drum switch. It goes to the 4th pole on the relay. Over time I figured out how the switch worked and realized there should be a jumper wire to the 4th contactor, so that it continues to be powered once the NO switch is released. I added the jumper and voila! - well almost. With the motor disconnected from the mag switch it latched when the drum switch was moved in either the forward or reverse direction. Add the motor and it runs in forward but not reverse - just chatters and won't latch. That's because the wild leg of the RPC is feeding the other end of the coil in reverse.
I did a variation of that to solve my problem. I connected a 2nd jumper from one of the line feeds to the other end of the coil so that the line feeds always power the mag switch. If my RPC supplied better power on the wild leg, I wouldn't have to do that.
I've thought about putting a light switch in the 2nd jumper wire to use as an emergency stop.
Yes. Definitely miswired. I got the wiring diagram for these from Clausing and as purchased, this lathe had clearly been rewired for some reason. Perhaps it worked on genuine 3 phase from the power company, but not when I hooked my RPC to it. The only thing missing from the Clausing wiring diagrams is the first jumper you need to keep the mag switch latched. For anybody reading this thread in the future, the jumper needs to go from T3 to the terminal labled #2.
Thanks for all the suggestions.
RWL
Reply to
GeoLane at PTD dot NET
It is a 220 / 440 V coil. There is a wiring diagram right on the coil showing you how to make it either 220 or 440 and I had the darndest time figuring out where those terminals were that they showed. I was wondering if it had been wired for 440 at the knitting mill where it used to live. When I finally realized where those terminals were, it was a "doh" slap your head moment". Then it was clear that it was wired for 220 and that wasn't my problem.
RWL
Reply to
GeoLane at PTD dot NET
I had been wondering about that too. As I mentioned in reply to Don, it took me until this afternoon to figure out where the terminals are that change between the two voltages. I confirmed it as wired for 220.
One problem was that a jumper was missing between T3 and the 4th contator terminal #2, which maintains power to the coil once the momentary switch has caused the coil to pull up. The second problem was that the wild leg of my rotary phase converter was part of the circuit when I was trying different things, and that leg would not hold the coil up despite the voltages being within 11 volts of each other between the lowest and highest pair of legs in the RPC.
Shoot me an email and I'll send you the wiring diagram Clausing sent me. That's not part of the manual. You can put the diagram on your web site.
RWL
Reply to
GeoLane at PTD dot NET
I'm using a 270-300 uf start capacitor on a cheap wall switch to get it going. It beats the pull cord I had been using. Currently I have 24 uf between L1-L2 and L2-L3. - cause that's the caps that I had at hand and wasn't sure what total uf to shoot for.
With the two run capacitors in place, I'm getting 240 - 251 - 244 (L1-wild leg, wild leg-L3, L1-L3)
I have a couple of more capacitors, but the one I'd like to try has me a little confused. It's 370 V so it *should* be a run capacitor, BUT it's a plastic case rather than metal like the others. The second confusion is that it's 40 uf and 5 uf. How do you tell which terminals to connect to get the 40 uf? I don't see anything on the lable although I believe one terminal is a little smaller than the other two. Which of the two terminals to use on that cap?
No need for me to get that complex. The two largest motors in the shop are both 2 HP and the idler on my RPC is 3 HP so that should handle both machines if I want to use it on both. The lathe would not work well with my VFD without rewiring. The Bridgeport uses the VFD and doesn't have a magnetic switch.
That's why I'm hanging onto the 5HP motor. If I ever get something that needs a larger RPC, I'll gang the 3 and 5 HP motors together to start the large machine.
RWL
Reply to
GeoLane at PTD dot NET
Check the coil voltages..make sure they are whatever is the proper value and make sure the secondary control transformer is wired with the proper input.
This is the normal fast check..look at the wiring configuration of the internal control voltage transformer to see what its wired for.
Gunner
Whenever a Liberal utters the term "Common Sense approach"....grab your wallet, your ass, and your guns because the sombitch is about to do something damned nasty to all three of them.
Reply to
Gunner Asch
[ ... ]
Is it possible that they had the wires from those terminals run off to an external panic stop switch somewhere? Perhaps a full-width NC treadle switch between the cabinets, or a master control for the shop to force *all* machines to stop in an emergency situation? (The best way to get the machinist's/operator's attention is to stop his machine. :-)
Glad you solved it.
Enjoy, DoN.
Reply to
DoN. Nichols

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