Mechanism of Master-pact ACB!!? 1

[albarkani]

Dear all,
here we have another questions about the master pact breaker.
I have 2 question

1- is about the spring charging motor

the spring charging motor use to open the breaker while re-charging the mechanism from discharge position to charge position?

I am planning to change the trip unit (micro logic 2.0a) but i thought it could be better to have some comments from you.

2- is about the quality of master pact breakers in general?

Regards.

 

[dpc]

The spring charging motor is used to compress the spring that closes the breaker. The closing action compresses another spring mechanism that is used to trip the breaker.

If you have a manually operated breaker, there is no motor.

 

[albarkani]

dpc,
yes you are right, but even if we need to re-charge the mechanism using the handle instead of motor, we cant do it while the engine online because it will trip the breaker and thats the problem.

and we have many engines at site and its working in auto mode (SCADA operation) and we should use motor.

currently we diconnected the motor

 

[RRaghunath]

albarkani,

I think you are wrong there - charging the spring manually should not cause trip of the breaker. If it is happening in your case, that is a problem to be looked in to (and can happen whether it is manual or motorised).
With regard to motorising the spring charging - If the breaker operation is not frequent and the closing is not required to be done from remote, the same is not a necessity.

 

[albarkani]

raghun,

i,m not wrong, thats the case with me , it opern the breaker in both cases manual or motorised.

i have 4 breaker having the same issue, thats why i was asking about the quality of masterpact breakers.

 

[genhead]

As already stated, the motor only charges the mechanism spring. Opening and closing of the ACB is by coils(solenoids) supplied from your control system.
Check the control wiring to the open/close coils. The closing coil (maybe both) is usually disabled until the spring is completely charged.

Are these new ACBs or existing?

ACBs (not just Masterpact) are not built like they used to be. There's lots of cheap & nasty "plastic" gears and other components, so one failed mechanism is not unheard of - but four in the same place is unlikey.

 

[albarkani]

genhead,

you are right the motor only use to charge the sring mechanism but it open the breaker at the same time of recharging the spring, in other words it open the breaker before it finsh the recharging process.

note that the control wiring is okay and the shunt trip, closing coil and undervoltage relay all are okay too.

the problem is that the breaker dont hold the closing position at the same time of recharging spring mechanism

 

[Zogzog]

"ACBs (not just Masterpact) are not built like they used to be. There's lots of cheap & nasty "plastic" gears and other components, so one failed mechanism is not unheard of - but four in the same place is unlikey."

Couldnt agree more, they make these things so cheap these days, the older ACB's like GE'S AK series, Westinghouse/C-H/Sq-D DS/DSII series, ABB K-line, etc. wee built to last, and they have for 30 or more years, if properly maintained and reconditioned evey 20-30 years they will continue to provide reliable service. the only problem with the older models was the trip systems, but that is an easy upgrade to modern tripping system for a fraction of he cost of new.

IMO the older ACB's lasted too long for the accountants at the OEM's, like making a car that lasts for 1,000,000 miles, it would put the car companies out of business, same goes for breakers, sems like they build them to last about a day or so past the waranty period.

As far as masterpacts specifically, there have been some recalls and problems with them have been discussed several times on this site, you can go back and search for these threads.

 

[ScottyUK]

(Slightly off topic)

Zogzog,

Did the Square D ever issue a recall on US versions of the ST series tripping units? M-G carried out a zero-cost replacement program on in the late 90's on the UK specifcation ST tripping units because of a component aging problem. In the UK the programme went under the name of 'Project Spring'.

[/Off topic]


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If we learn from our mistakes I'm getting a great education!

 

[slavag]

Hi.
Of course possible some series problem with your ACB.
I haven't expereince with this type of ACB, but from lot of guys I heard a good words about this ACB.
Are you try connect to technical support?
Please attach scheme of connection.
Something strange.
Best Regards.
Slava

 

[wbd]

There may be a permisssive contact that is welded shut. What is the control voltage? Is it possible that the breakers have a control system built for 125Vdc but the voltage is 250Vdc? Sounds impossible but if all four bkrs are behaving the same, need to look at what is common. Does this occur if breaker is out of cubicle and on the floor?

 

[FreddyNurk]

A couple of thoughts:

You stated that both the undervoltage and shunt trips were wired correctly. From what I can remember, certain types of Masterpact (and as I understand it, Masterpact is M-G's LV offering for ACBs) can only have either the shunt trip or the undervoltage coil fitted, that is, they're mutually exclusive. To this end it would be prudent to double check whats fitted to the breakers.

Also, when my former company used such breakers, it was 24V control, with 240V motor charging spring, and I believe 240V undervoltage trip. The upshot of this (you mentioned generators) was that you could only charge the closing spring when the generator that was connected to the breaker was running, and the undervoltage trip was also wired to trip the breaker if the generator shut down for any reason.

It would be worth checking the wiring at your installation to see if such features have been wired that way.

I must admit I'm a bit confused as to your site's operation, as I don't see a need to charge the spring if the breaker is closed, and as DPC stated, the motor only charges the closing spring. I admit I'd never had to look at charging the spring when the breaker is closed, but then again, theres probably a lot of things I've not yet seen. I wouldn't have thought that recharging the closing spring whilst the breaker is closed would trip it either though.

 

[albarkani]

FreddyNurk, and all

the breaker that we are using is having (shunt trip, undervoltage relay and closing coil.) see the line bellow

http://web.schneiderelectric.bg/bgnew/downloads/ed/lv/masterpact.pdf

In our operation, the spring charing motor should be charged after the closing of the breaker. because if its discharged and engine run through scada signals in this case the breaker will not close and need some one to recharge it manualy.

today i want to clear one thing, is there any interlock or something like that between the main closing shaft and spring charging motor??

 

[DanDel]

albarkani, I think the consensus here is that there is something wrong with either your C/B or the control wiring for the shunt trip. The C/B is designed to be closed and charged at the same time.

 

[dpc]

There are generally limit switches and/or torque switches in the breaker mechanism that can cause problems.

I once saw a new (at the time) I-T-E breaker that when first powered up charged up the spring as expected, but then went right ahead and closed itself. Luckily, no one was hurt.

The problem was a misadjusted mechanical linkage or limit switch - I can't remember which.

Anyway, this is not normal behavior if I'm understanding what you are telling us.

 

[albarkani]

dandel and dpc,

thanks alot

threre is nothing wrong with the control wiring because today i remved the C.B out of the engine and find out this points:

1- i close the breaker, trying to recharge but get the same thing it open when i at the same time i,m charging the spring.

2- the spring used to push the mechanism to close the breaker, am i right.

3- when recharing the spring i figured the main closing shaft return back to open state, means there is noting holding the mechanism and main closing shaft to stay on closing state, and the spring is used to hold the mechanism before instean of any mechanical lock or something else.

i dont have exp. with the mechanism and how it work.
but my question now is:

is there any thing that hold the mechanism to stay on closing state even if we recharged the spring.

 

[dpc]

I think you need assistance directly from manufacturer or authorized representative. We could exchange a million words and still not be any closer to resolving. Someone who knows how the breaker is supposed to work needs to lay eyes on it.

 

[Zogzog]

Send it out to a breaker shop, cant do much with this in the field. Or if it is still under waranty, have the OEm come out to fix it or replace it.

 

[dpmac]

When the breaker is removed from the cell it will not close. It will charge, but it will not close without the small defeat bracket that temporarily mounts on the side of the breaker to allow testing. It will go "Trip free" without this temporary bracket. This assumes a basic NW ANSI breaker. I am unclear on the exact type you have.

 

[DanDel]

albarkani, what you are describing is a 'trip-free' condition, where the open C/B is charged, and when a close is attempted, it 'trips-free', which means the mechanism releases the spring charge, but it doesn't close the contacts.
dpmac has given you the correct info; that particular C/B will trip free outside the cubicle unless that bracket is installed. If you are not familiar with this C/B, you should contact the manufacturer or a reputable testing company for field service.