Softstarters-FAQ

• Q: What is the control voltage for the PST softstarter?

  A: The PST softstarter has three different voltages levels on it. The Three phase Motor voltage, the (120-220)Vac Supply voltage, and the 24Vdc control voltage. The 24Vdc can be supplied extenally by removing the jumper between terminal 8 & 9. Then put your Negative on Terminal 8 and and use the Positive as a signal to the Stop/Start terminals.

• Q: Why does my softstarter have a fault for an SCR

  A: Possibility the the motor is coasting to a stop and the Regeneration voltage is induced back into the load side of the softstarter. Check the SCR's without power to see if they are shorted.

• Q. Is there any requirement to put a main contactor in series before the softstarter?

  A. The softstarter does not require a main contactor but ABB recommends the use of one for emergency stop and/or trip of the overload relay. In some applications an MCCB can be used instead of the main contactor.

• Q. Can I use a softstarter if the ambient temperature is higher than the recommended value during operation?

  A. The softstarter can normally be operated at a higher ambient temperature during operation if the rated current for the unit is derated according to the manufacturer's recommendation.

• Q. Is it possible to run a softstarter with one thyristor (SCR) shorted?

  A. Yes, it is possible but not for all types of softstarters.

• Q. What applications are suitable for soft stop?

  A. Pumps and conveyor belts loaded with fragile products are the two main applications suitable for soft stop.

• Q. What is the advantage of using by-pass?

  A. Reduction of power loss

• Q. What utilisation category should be used for the main contactor and the by-pass contactor?

  A. Main contactor: always use AC-3.
  By-pass contactor: it is possible to use AC-1.

• Q. Why does the softstarter indicate a fault when the start signal is given to the main contactor and softstarter at the same time?

  A If the main contactor is closed too late the softstarter will indicate this as a phase loss fault. Delay the start signal to the softstarter by approx. 0.5 sec. to solve this phenomenon.

• Q. Can I test a softstarter without using a motor?

  A. No, this is not possible since there will be no current going through the softstarter and some types will also indicate loss of load.

• Q. Why does the overload relay trip during start?

  A. Possible reasons can be one of these or in a combination:
  -too low current limit
  -too long ramp time
  -too low initial voltage
  -wrong tripping class on the overload
  -wrong setting on the overload

• Q. Do I need a separate overload relay when using a softstarter with built-in electronic overload and by-pass?

  A. If the current transformers of the softstarter can be installed so that the measuring can be performed when by-passed a separate relay is not required; otherwise yes.

• Q. Can I use the same softstarter at both 50 and 60 Hz?

  A. It is possible with all types of ABB softstarters as long as the curve is sinusoidal.

• Q. What voltage fluctuations are allowed for the softstarter?

  A. The minimum and maximum value where we can guarantee full function is -15% to +10% of the rated value.

• Q. Do I always have to use semi-conductor fuses?

  A. When using semi-conductor fuses a type 2 co-ordination can be achieved. It is possible to use an MCCB or MMS instead but then with a type 1 co-ordination.

Product Selection

• PSR Softstarter

• PSS Softstarter

• PST Softstarter

• Technical Support

  Ph: 1-888-385-1221
  Email: lvps.support@us.abb.com