SOFT STARTERS FOR OIL PUMPING MOTOR

[neca]

I am e new user of soft starter. I need to know if there is someone that has used a soft starter with an electrical motor of a Beam-type oil pumping system. This kind of load is no constant torque.
This system has 3 cycles:
- In one cycle, up swing, the motor has all load and there is high current draw.
- In other one, there is no load.
- In the last one, down swing, there is low current draw and may be generation.

I really appreciate some information about your experience with this kind of application.

Best Regard,
NECA

 

[tmahan]

Should not be a problem. Once a softstarter has finished starting the motor (figure a 5-10 second ramp time for a walking beam) the softstarter pretty much just acts like a contactor. There probably is a contactor in parallel with the softstarter in fact.
Since there is no frequecy conversion no special concerns exist with regards to overhauling loads.

The most likely problem to surface is the softstarter tripping on some manufacturer specific version of "underload". just make sure you can disable that feature if it is equipped on the model you are considering.

In this forum your most likely going to get manufacturers like myself answering this question. If you want people who are actually using softstarters for this application you may want to try one of the oil and gas specific forums

 

[Marke]

Hello neca

With this type of application, the load torque is cyclic and you may need quite a high torque to get it going. This will result in a high start current requirment. I would suggest that you ensure that the starter is capable of 450% starting current for 10 seconds. Theonly other problems to be aware of are: 1) Undercurrent protection setting. Set this below the magnetising current of the motor or disable it. 2) Energy savings - set to OFF if included as part of the soft starter functionality.
I have used soft starters in these applications without problems.

Best regards,

Mark Empson

http://www.lmphotonics.com

 

[tmahan]

An additional problem that I had not considered has actually shown up on a similar application.

Depending on how the softstarter manufacturer detects for shorted SCR's there could be phantom trips.

In cases where shorted SCRS are detected by a voltage drop across the SCRs regeneration may reduce the drop across the SCR's low enough that the softstarter is fooled.


This should not be a problem for those units where SCR failure is detected only by current flow. Ask the softstarter manufacturer what their reccomendations are regarding this problem (if it occurs). Most have redundant SCR failure detection methods so you may be able to disable voltage drop detection

 

[jbartos]

Suggestion: Visit

http://www.energy.ca.gov/pier/reports/500-03-062.html

etc. for more info