PCS Soft Starter
PCS Soft Starter
(OP)
I am having a problem with a Sprecher and Schuh PCS-037-480v soft starter. Intermittently it is going into Phase loss/open load fault. There are 5 other pumps within the switchboard all controlled the same way and we have no other issues, I have replaced the starter and still have the same issue, I have swapped both the existing starter and the new starter with other starters in the switchboard and the fault always moves with the starter. Logic says we have a starter issue but I have put 2 new ones in and still it continues to fault.





RE: PCS Soft Starter
I'm, not an expert on the A-B / S+S soft starters, but generally this kind of issue is a result of a current detection problem. Some soft starters detect phase loss by detecting a current level in at least one phase that is below a specific threshold, let's say 20% FLA. The nuisance can be that in your case, the motor load is so low that even thought you are not losing one phase, the current in all three phases is below the threshold level and triggers the fault. You8 may need to disable the Phase Loss detection to avoid it.
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RE: PCS Soft Starter
Is the problem always on the same motor?
Keith Cress
kcress - http://www.flaminsystems.com
RE: PCS Soft Starter
RE: PCS Soft Starter
Bill
--------------------
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Jimmy Carter
RE: PCS Soft Starter
After your contactor comment, it now sounds like you are either closing the contactor too late when you start the pump or you are opening it too soon when you stop the pump.
RE: PCS Soft Starter
There is a couple of technotes on the A-B knowledgebase in regards to this. Try technotes 22373 & 59588. They are based around the A-B equivalent SMC-3 but should help regardless of the label on the front.
RE: PCS Soft Starter
RE: PCS Soft Starter
Try the following. You may have to register to be able to see the technotes.
http://rockwellautomation.custhelp.com/
RE: PCS Soft Starter
RE: PCS Soft Starter
Is your installation an inline (3-wire) or inside delta (6-wire) connection as the soft starter may be configurable for both?
I think the more likely problem may be with either your contactor bouncing/dropping out or perhaps a loose connection somewhere on either the line or load side of the soft starter possibly even in the motor terminal box. It may be worth a quick check of all connections. A faulty isolator between the starter and motor may also cause this alarm.
RE: PCS Soft Starter
RE: PCS Soft Starter
RE: PCS Soft Starter
RE: PCS Soft Starter
We know that it can and does occur when the run current is less than 50% of the max FLC setting and suspect this is influenced by current imbalance and wave shape.
For the record we more some 1400-1500 PCS starters per annum and on the rare occasions when nuisnace phase loss/open load tripping occur, we have been forced to offer an alternative product/solution.
RE: PCS Soft Starter
RE: PCS Soft Starter
RE: PCS Soft Starter
Soft start will allow the motor to develop and increasing amount of torque as it accelerates through to operational speed and is great for applications where the starting torque requirement is variable ie from one start to the next. Whilst it does reduce starting current,this is also influenced by starting time and the driven machine and can therefore approach levels similar to DOL (Across The line) when the starting time is very short and/or where the driven machine is highly inertial.
Current limit on the other hand holds the current fixed during the starting period and is therefore better in applications where the emphasis is on reducing starting current and voltage drop on the line. If the current is set too low however, the motor will not develop enough torque to accelerate the driven machine to rated speed, so it needs to be set correctly.
I really don't expect changing from Soft Start to Current Limit or vice versa will reduce your nuisance trip issue, but as you have nothing to lose, it's worth a try.
RE: PCS Soft Starter