braking resistors overheating

My 71 modular drive shows evidence of severe overheating from the braking resistors. The problem has been partially repaired, but some wires are missing and the cause of the problem is still speculative. I have yet to apply power to the lathe, but I am in no hurry, since the gearbox just came off and I am in the process of cleaning and painting the lathe.

Carl came over and together we came to the conclusion that the current relay, the part labeled QSD (what does that stand for?), is a likely cause.

The wiring repair needed is to replace wire that overheated, and some of it is missing, so I need some help. The wires from the braking resistors go to the terminal strip connections labeled 41 and A2. What gauge wire should be used? The wire being replaced is 12 gauge, but the wire feeding the terminals is much larger.

How do I verify correct operation and adjust the current relay, QSG? Can someone explain how it works, what it senses, and under what conditions it trips?

And one more question: where can I find the gasket material used to seal the modular drive compartment? Mine has deteriorated, but considering the age of the lathe and the amount of solvents, etc. it has done a good job. It is a round soft rubber, about 1/4" dia.

-Dave

Dave the QSD is the quick slow down relay, If the lathe is running at a high rpm, and you turn the speed control to a lower RPM rapidly, the QSD will place the brake resister into the circut and slow the machine down rapidly to the new slower speed, but if you turn the speed knob slowly the QSD does not kick in.
My 1983 lathe had problems in this circut and the compensating circut,
I found on my lathe, that it had alot of prolems, some from people tryin to fix it in the past.
I think the best thing to do on these machines is get the print from Monarch for your machine{Monarch made changes through the years] And check all the wires from where the AC power comes in, to the DC to the motor.
I found loose and damaged conectors, misplace wires ect. Stuff happens over 32 years.
Don
Other than that I really dont know how it works.

[This message has been edited by donie (edited 12-11-2003).]

"My 71 modular drive shows evidence of severe overheating from the braking resistors."

The QSD relay is sticking.

The dynamic braking (DB) resistors are intended for intermittent use, under a second or two, only, followed by a cooling-off period of many times the on period.

(DB resistors in VFDs are similarly rated).

QSD = Quick Slow Down.

In the earlier machines, the DB resistors were placed across the armature whenever F and R were both not true, IOW, when the armature was not energized.

Also, in the earlier machines, the two DB resistors were 4.8 ohms each; in the Modular machines, these resistors are 8 ohms each.

The Modular machine has only one normally-closed contacts in the F and R contactors (named 2MR and 2MR in the Modular machines); the earlier machine have two.

The QSD relay provides the same function as the (missing) set of normally-closed contacts, only in a much more elegant (and complicated) way.

PeterH - "The Modular machine has only one normally-closed contacts in the F and R contactors (named 2MR and 2MR in the Modular machines);"

I believe Peter meant 2MR and 2MF. Everyone probably figured it out but...
Sorry.

Peter what do you mean when you say "eariler machines"? Is it earlier Modulars or earlier than Modulars or?

Steve

[This message has been edited by andromeda (edited 12-11-2003).]

Dave,
If you need someone to take a look at their machine and tell you what they have, I'd be happy to do so.
Do you still need to know the gauge of wire that goes from the terminal strip 41 and A2 to the braking resistors?
Steve

Steve, the wire size info would be helpful; the 12 ga. wires that are being replaced had been heated to the point that the insulation was burned off near the braking resistors. The mounting board was also burned.

Peter, when you say "more elegant (and complicated)" I assume you mean the current sensing is more complicated, but allows better control, even new capability as Donie points out.

Thanks for the explanations of what this circuit does, but since it has to sense a change in speed from high to low, as well as on to off, adjustment must be somewhat tricky.

-Dave

"Peter what do you mean when you say 'eariler machines'? Is it earlier Modulars or earlier than Modulars or?"

By "earlier", I meant pre-Modular, and that includes WiaD and M-G (but not Sunstrand).


"Peter, when you say 'more elegant (and complicated)' I assume you mean the current sensing is more complicated, but allows better control, even new capability as Donie points out."

Yes, the QSD relay method, which is *current sensitive* does indeed provide both a new D/B-like function, and also the new function of a controlled slow-down (rather than a "coasting") function, when changing speeds manually (or otherwise).

Clearly, a combination of the specific control functions provided by all the drives (M-G, WiaD and Modular) could be useful, but then the drive would indeed become "complicated" ... perhaps to the point of diminishing returns.

Dave,
I checked my wiring diagrams and found that I do not have a spec on the wires that run from R10 and R11 to A2 and 41 on the terminal block. I have a spec on all of the contactor panel wires just not the tube panel wires.

I did count about 50 coductors and measure the wire size to be .131 and the insulation to .167 if that helps?
Steve

Since the wires to the braking resistors presumably only carry current when the resistors do, the size shouldn't be fussy.

The insulation was likely burned when the resistors overheated.

The resistors will carry armature current until it dies out, as the motor dumps its rotational energy into the resistors. So a sensible size like 14 ga should be a minimum just on principle. 12 Ga would be fine also.

Braking resistor in cranes

J Tiers said:

Since the wires to the braking resistors presumably only carry current when the resistors do, the size shouldn't be fussy.

The insulation was likely burned when the resistors overheated.

The resistors will carry armature current until it dies out, as the motor dumps its rotational energy into the resistors. So a sensible size like 14 ga should be a minimum just on principle. 12 Ga would be fine also.

Click to expand...

By
First i want to thank everybody for their knowledge sharing, but still i am not able to solve my problem.
"I have a overhead crane it has problem with its braking resistor for long travel.. But when I connect the braking resistor to the drive it starts heating to very high temperature Even the crane is not in motion, I tried to adjust the parameters but all in vain.. Could you help me solve my problem.. I am using sk commander inverter EMCSKC3400400. Q

Either you are connecting the resistor incorrectly or the inverter is bad.

Quaiser said:

First i want to thank everybody for their knowledge sharing, but still i am not able to solve my problem.
"I have a overhead crane it has problem with its braking resistor for long travel.. But when I connect the braking resistor to the drive it starts heating to very high temperature Even the crane is not in motion, I tried to adjust the parameters but all in vain.. Could you help me solve my problem.. I am using sk commander inverter EMCSKC3400400. Q

Click to expand...

The braking resistor should be on the terminals as shown in the manual:



If it is connected that way then there's something wrong in the programming that's causing power to be run through the braking resistor all the time. It might be best to look through the programming to see what's been set, reset to defaults and to reapply those functions you know won't put power through the braking resistor.

This thread was hijacked at POST #10. It should be deleted from that point on, and that poster should start it elsewhere, as the question they ask is entirely irrelevant of the OP.

There is no relationship between the MONARCH 10EE braking and the hijacker's intervention.

DaveKamp said:

This thread was hijacked at POST #10. It should be deleted from that point on, and that poster should start it elsewhere, as the question they ask is entirely irrelevant of the OP.

There is no relationship between the MONARCH 10EE braking and the hijacker's intervention.

Click to expand...

Seconded. Not JUST irrelevant. Contrary to.