500hp unloaded motor jerks on startup using soft start controller 2

[ronnied]

Can anyone explain why a soft start controller would cause a motor to jerk on startup. We had the manufacturer of the motor test the power and noticed the amps go up to 3000A, and the sinewave amplitude rise above and fall zero as a whole.

 

[rbulsara]

I beleive the start up voltage and current ramping is adjustable. You may want to check the inital voltage and rate of ramping on the starter.

If you are applying more than 50% voltage you will see a 'jerk'. You may have to play with the adjustments.

 

[jraef]

In addition, some soft starters have a "kick start" feature which applies nearly Across-the-Line voltage for the first 2 seconds. It is supposed to be only for high friction loads to help them "break free", but if used or left on for no reason, defeats the entire purpose of having a soft starter.

Go ahead and post the mfgr and model, someone can probasbly help you find the problem. It should not do that.

"Venditori de oleum-vipera non vigere excordis populi"

 

[Danfossegypt]

hello ronied

i faced this problem before
all you want to do is to initialize your controller
and readjust the parameters again

sincerly

 

[jraef]

Danfossegypt,
How can you say that when we do not know the make, configuration or anything else about the starter? That may work on a Danfoss sytarter and (most Microsoft products), but it certainly will have no effect on the vast majority of soft starters I am aware of.

"Venditori de oleum-vipera non vigere excordis populi"

 

[GGOSS]

Hello Ronnied,

Soft starters ain't always soft starters. As many have already outlined in the above, the symptoms you are describing could be the result of poor starter set-up, but could also be related to the type of soft starter you are using.

In order to guide you further, please provide an outline of the application (driven machine) and the make/model of the soft starter.

With that information available forum members may be able to suggest revised settings.

Regards,
GGOSS

 

[Marke]

Hello Ronnied

This sort of problem can occur when the supply is not solid enough to start the motor. If you attempt to soft start a motor on a very weak supply, you will get a drop in the supply voltage, plus some distortion of the supply voltage waveform. This can interfere with the operation of some soft starters and cause the problems that you describe.

Like the others, I would like to see more fact and data in order to help you further
Best regards

Mark Empson

http://www.lmphotonics.com

 

[ronnied]

Thank you for responding to my query. Maybe I was not clear, this is a intermmittent problem where the motor does not start, and jerks (short partial turns like it is sticking or the controller is misfiring). The application is for a potable water pump station. The controllers are Cutler-Hammer EA760. We have had the manufacturers for the Pump/Motors and the Controllers out checking their equipment, power quality, etc and all we got was finger pointing but no solution. The station is running across the line starting just fine but taking heavy fines from the municipality. We need to be able to point to some component, issue, etc that would cause this in a softstarter, can anyone help?

 

[oceanamber]

Ronnied

You say an intermittent fault. Is this potable water pumping station in the middle of a field, fed from an L.V. source. Can I assume there are other motors running? What is your voltage like? At the end of a long cable you may be running short of volts.

 

[jraef]

ronnied,
This is a problem with the soft starter for sure. The old EA series had a potential problem with one of the ICs (thick film actually) failing intermittantly, probably from static, moisture or some other external influence. It controls the firing pattern of the SCRs so when it gets corrupted, the SCRs fire randomly causing that severe "cogging" effect because you are putting DC pulses on the motor winding. It is an analog circuit, so when the condition goes away, it works normally again. You will NOT likely find anyone left at Cutler-Hammer that knows this, they were all let go when they closed the plant in Oldsmar Florida. They stopped supporting that product a few years ago, there are no parts available as far as I have heard.

Here is what you can try:
1) Make sure that internal condensation is not occurring inside your starter. Keep a stip heater powered up inside of it, especially when not in use. It does not have to get extremely cold, just 40F for moisture to form on the warm surfaces. Since you say that it is portable, this may be problematic. You can also try adding Corrosion Inhibitors like those available from Hoffman (and others). They work OK when power isn't availble, just not as well as a strip heater.
2) Keep it clean and dust free so as to help prevent static discharges on the PC board. Use an electronic spray cleaner, or WD-40 if nothing else is available.
3) Have the board refurbished by a 3rd party, i.e. Electrical South. Not cheap, but probably the only ones left with drawings and experience to do it.
4) Buy a new soft starter and chuck that old EA.

"Venditori de oleum-vipera non vigere excordis populi"

 

[jraef]

Oops, I read "portable" and you said "potable"!
Must be my southern accent...

Everything else still applies though.

"Venditori de oleum-vipera non vigere excordis populi"

 

[ronnied]

Do you have contact info for Electrical South?

 

[jraef]

http://home.elsouth.com/

"Venditori de oleum-vipera non vigere excordis populi"

 

[Barry1961]

I heard that Saftronics had picked up the old EA line and continued to produce them for awhile at least. Probably a long shot.........

Barry1961

 

[jraef]

Barry1961
No that is not true. Probably stems from confusion based on the fact that Saftronics' old starter product line was called "EZ" and their current product is called "AS". Nobody picked up the old Cutler Hammer EA, it died a quick and meciful death when that plant closed down.

"Venditori de oleum-vipera non vigere excordis populi"