14 replies to this topic

[chaterpilar]

Hi !!

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..?

Chaterpilar

[marke]

Hello chaterpilar

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??

Best regards,

[chaterpilar]

No
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.

[jraef]

Did you read the manual?
Here is what it says regarding the OCF fault:

Overcurrent:
• 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)

[chaterpilar]

Thanks Jraef, but i did read the manual, before throwing it on this forum.

I am trying to understand why the OCF fault should come only when STOP command is given.

Chaterpilar

[jOmega]

Chatepilar,

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.

Curious...

[chaterpilar]

Jomega, The motor drives gear pump (hydraulically driven mixers) and comes to stop immediately and has no over-run.

Chaterpilar

[jOmega]

Chaterpilar,

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 ....

[kezetrum]

Hi Chaterpillar and all,

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..



regards

new member

[jraef]

Well, trip conditions on digital controllers such as this always have a program code associated with them, a list of criteria for which the mP says constitues a problem that must be displayed on the interface. So if you look at their list, an "impending short in the load" would most likely mean that it is picking up a significant amount of current flowing in the circuit that would not be normal for the programmed motor, so it would not be that in your case because you say it is tripping on Stop. If you then check the bypass contactor and it does not have a welded or stuck contact, then the only remaining issue pertinent to you is the "internal fault". The definition of that can only come from Telemecanique, because nobody else will know the internal criterea for displaying that trip condition. You may want to look inside for anything obvious such as an SCR or heat sink tracking to ground or phase-to-phase, but other than that it is going to take correspondence with the manufacturer.

[chaterpilar]

Thanks everybody ...i will come back to you with the reply from manufacturer

chaterpilar

[GGOSS]

We have just replaced an ATS48 displaying the same fault. The customer was unable to get an answer/resolution from the supplier! Could this be a common fault?

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.

Regards,
GGOSS

[jraef]

To be honest, I am not a fan of the Telemecanique soft starters (but I have to be careful because one never knows where the next paycheck is coming from!). I only know about them from recent experiences as a consultant and some past experiences with older versions. I too feel as though they have little desire to help customers here in the US, I had no idea it was happening all over.

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.

[kens]

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!!

Ken

[chaterpilar]

Thanks All, for the inputs.

We found the firing card defective. We changed it and the fault has not reoccured.

Chaterpilar