Softstarter on Pump2
Softstarter on Pump2
(OP)
Please share your views for failure analysis:
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I dont intend to depict a product inferiority in here or criticize its manufacturer. If anyone had known this, please keep it in yourselves.
This post is to provide a root cause failure views in this forum only .
Thanks,
bil





RE: Softstarter on Pump2
Can you examine the point at which the lug broke away and see if it has the characteristic crystalline appearance of a brittle fracture?
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Sometimes I only open my mouth to swap feet...
RE: Softstarter on Pump2
Scotty's thought is a good one too!
Keith Cress
Flamin Systems, Inc.- http://www.flaminsystems.com
RE: Softstarter on Pump2
Itsmoked, logic board from OEM has protective cover on it as specified. But in actual installation it's nowhere to be found. I guess you're right with your guess as mine. There is high probability that a conducting pieces might get contact with PCB.
Any more wise guess of this failure?
Thanks,
bill
RE: Softstarter on Pump2
I have seen this kind of behaviour a few times, we use a similar patent on some of our older rectifier stations. It is used as a source of dc supply to our overhead pantograph systems. The difference is that we are using normal diodes, while you are using SCRs.
Such flashovers on our stacks normally started after
:some rain or with high humidity present.
:failure of the bolt insulation (in your picture it would be the blue insulation studs next to each SCR)
:Diodes not been torqued correctly.
Is there a way that you can open some of those chips and take some pictures? I have a list with causes for typical failures - eg. misaligned heatsinks, incorrect clamping, blocking voltage breakdown, overclamping, high surge current (di/dt), dV/dt failure, etc, etc.
Regards
Ralph
Failure seldom stops us, it is the fear for failure that stops us - Jack Lemmon
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RE: Softstarter on Pump2
JRaef.com
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RE: Softstarter on Pump2
Ralph, installation factor is also accountable as you enumerated above. But i classify it as less probable.
Jraef, i'm much convince as what itsmoked pointed out. Noting that this board is brand new as purchase.
Other way around;
1.) Since Control board is new, is there a possiblity of ESD (electrostatic Discharge) issue here?
2.) How about missing the cautions upon adjusting the torque limit and time rheostats where carried out while the board is energized?
3.) How about some possibilities like carelessness, safety precautions, etc? I appreciate if anyone could add..
However, i can't disregard Scot's view. As preventive measure, i would recommend to insulate the Gate terminal lugs like a sort of shrinkable tube insulator to prevent the shorting path between gate and anode terminal. Would you agree with it, Jraef?
Thanks,
bill
RE: Softstarter on Pump2
I think something along the lines of RalphChristie's scenario is correct.
Keith Cress
Flamin Systems, Inc.- http://www.flaminsystems.com
RE: Softstarter on Pump2
Check the SCR leads where they're twisted together. I've seen it before where there was an insulation failure that shorted the lead to the heatsink or each other and caused that.
Scotty's description is quite possible. Once it flashed during the fault it would be hard to tell if it burned off or broke off too.
Otherwise, I would suspect the flashover started at the phases and then the card card failed which caused phase-phase circuit tracking on the board which then blew off the gate lead.
The other possibility is that the SCR failed and put a large gate to cathode voltage out of that lead which overvoltaged the gate circuitry on the card and caused it to flashover and also blew off the gate lead at the same time causing the 3-phase flashover on the scr phases. I can't see this happening if there was no motor connected though.
You say the motor was disconnected at the time? The unit was powered back up again though? I can't see the insulators, water or dirt on the clamp between the phase or SCR torque having an effect if there was no motor connected. In this case, the line and motor heatsinks would be at the same voltage due to SCR leakage resistance. Unfortunately, this also somewhat shoots down SkottyUK fault description. If both heatsinks were at the same potential then the lead shorting to the anode side would not cause a flashover.
RE: Softstarter on Pump2
"you say the motor was disconnected at the time? The unit was powered back up again though?" I guess you're right, this would be the possible.
Prior to the occurence, this board (new) was installed while SCR assembly is already installed and operational. The installation was carried out in order to test the functionality of the board. Adjustment were made on the board (rheostat) such as torque limt, time setting, current limit as well as the dip switch for motor FLA. Consequently, start and stop of motor (dont know how many times) is obvious while refining the board's adjusments until a adjustment was attained. Motor terminals were disconnected in order to pull out the tested board for safekeeping as spare. Then, whoosh! it ignites!
I suspect that a redundant adjustment of rheostat was carried out while main power supply is energized and noting that motor cable was disconnected. Any comment?
With above description, i never disregard the probability of poor workmanship, carelessness, safety awareness to the board adjustment, etc.
Thanks,
bill
RE: Softstarter on Pump2
Here's mounting board of SCR and Control Board:
http://i
See, what you got..
RE: Softstarter on Pump2