Posted 10 November 2006 - 06:35 AM
In one of our ATS48 softstarters we get OCF ( overcurrent) fault when we stop the motor.
The motor runs well and has no problem running continuously.....however when we stop the motor, the display shows OCF,and can be restarted after resetting the fault.
The question is why the fault comes when we stop the motor..?
Posted 10 November 2006 - 07:57 AM
I have seen this where the motor was running close to an overcurrent trip, and then went into a soft stop.
When you use soft stop, there is an overcurrent situation similar to that during start. If the motor is close to tripping, then a short period of overcurrent could cause an over curent trip.
Does this seem to be true in your case??
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Posted 10 November 2006 - 01:18 PM
Marke the motor is running presently at 50% of its full load current.
There was one problem in the starter few weeks ago when the starting relay was jammed and during power changeover the starter came ON and the Main breaker tripped.
Posted 11 November 2006 - 01:41 AM
Here is what it says regarding the OCF fault:
• impeding short-circuit on soft starter output
• internal short-circuit
• bypass contactor stuck
• soft starter is overloaded (it appears this may not apply to you)
Disconnect power to the soft starter, then:
• Check the connecting cables and the motor isolation.
• Check the thyristors.
• Check the bypass contactor for a stuck contact.
• Check the parameter value bSt in the menu drC (page 49). (this probably doesn't apply either because it has to do with the Start mode)
Posted 11 November 2006 - 12:16 PM
I am trying to understand why the OCF fault should come only when STOP command is given.
Posted 12 November 2006 - 09:59 PM
You haven't as yet identified the type of load that the motor is driving.
Q. When you initiate a stop, is it possible that the load could be overhauling the motor and creating a regenerative condition ?
For example such a condition of this type occurs when a lift pump is stopped and a there is no check valve in the discharge line to prevent flow reversal that drives thru the pump, overhaulling the motor into a regenerative state.
Posted 13 November 2006 - 03:25 AM
Posted 13 November 2006 - 01:32 PM
Thank you for that detail.
Q. Have you hung a Clamp-On Ammeter on a motor lead.... and monitored it when a STOP cmd is initiated ?
If so .... what did you observe ?
T N X ....
Posted 13 November 2006 - 03:30 PM
I have never use ATS48..but the same case ever came to me with the differ product brand..
my experience..i come to check the programming back, check the excess load, the dc brake volts set to
high. .and how about the ramp rates of the deceleration to stop according to motor applications that should
minimize the nuisance tripping..
Posted 14 November 2006 - 01:53 AM
Posted 14 November 2006 - 03:15 AM
Posted 16 November 2006 - 02:01 AM
If the inputs on the the ATS48 are low voltage eg 24V active driven by volt free contacts or similar, I would also be looking at induced electrical noise as being a potential cause. Make sure all low voltage cables are kept well away from supply cables, motor cables and any cables feeding contactor coils etc.
Posted 16 November 2006 - 04:07 AM
I haven't actually specified one since I used some ATS43s on a project in 1990. We installed 6 units on a very simple centrifugal pump project and had 8 failures in the first 9 months. Yes, that means 2 of them failed twice! At that time, Square-D had just been bought by Schneider, who decided to jettison the Square-D Alpha-Pak SS units in favor of the ATS43. Unfortunately here in the US, there was nobody in the Square-D service organization that knew anything about the ATS product. We eventually removed them all and installed Benshaw and had no more problems. When I later worked for Motortronics, we had several occasions where the ATS46 and 48 were used and failed, only to have the Motortronics product succeed in the exact same installation. Recently as a consultant I have had to do start-up and troubleshooting in the field on a few ATS48 units. They seem to work better than I had experienced previously, but I don't like their programming. Now it appears from these statements that they may have other issues as well.
I know that isn't helpful to your situation now chaterpilar, I guess I'm just letting you know that you are not alone in your frustration. I'll be watching to see if you do get some satisfaction from Schneider. They need to recognize that a lack of response to a problem with their product is much much worse than having a problem in the first place.
Posted 16 November 2006 - 05:07 AM
They need to recognize that a lack of response to a problem with their product is much much worse than having a problem in the first place.
No help at all for this discussion but I cannot agree more with jraef, with the technical and price differentials closing the only differential is often service response. If a product fails generally it will be on a critical piece of kit and then you can find out how good your supplier really is. 3 am is always a good time to test out how much they value your business!!
Posted 26 November 2006 - 02:57 PM
We found the firing card defective. We changed it and the fault has not reoccured.
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