Anybody ever put an ATS22 (schneider electric) soft-starter after a phase converter?

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Rsteenson

Member
I installed an ATS22C11S6U soft-starter on a 40 hp 230v motor. The motor is being fed from a "Ronk" phase converter. I have had nothing but numerous faults on the soft starter from short circuit to phase loss to over current. My voltages are showing the same as a hi-leg delta system.....although "c" to "b" phase is showing almost 280 volts, which makes me curious. The motor has been run on the phase converter for a couple years but my customer has had problems with the original across-the-line starter. (what a surprise on a 40 hp motor, right?) why the original sparky didnt install one is beyond me. any help would be greatly apprecciated!
 

templdl

Senior Member
Location
Wisconsin
Have you talked to Schneider electric about the application? They would be the ones who would give you an accurate answer.
 

defears

Senior Member
Location
NJ
Some phase converters make a (dirty) 3rd phase. Electronics on that phase can sometimes not work. Make sure the control circuit in the soft start is not on that phase.
 

jim dungar

Moderator
Staff member
Location
Wisconsin
Occupation
PE (Retired) - Power Systems
That soft start is factory set with some pretty tight incoming voltage tolerances. You can adjust one of the parameters to accept a very sloppy input.
 

Jraef

Moderator, OTD
Staff member
Location
San Francisco Bay Area, CA, USA
Occupation
Electrical Engineer
There are very few soft starters that are going to tolerate being fed from a rotary phase converter. Although the capacitors on the RPC will make the voltage APPEAR normal on a meter, and the differences are not as big a deal directly on an induction load like a motor, a soft starter has to deal with things like current rise times etc. The charging current of a capacitor has a very steep wave front as far as the SCRs are concerns, much the same as a dead short. What can happen is that the high dV/dt (change in voltage over change in time) can cause SCRs to "self commutate" meaning they fire on their own, i.e. when you don't necessarily want them to. Once SCRs begin firing at the wrong time, the Soft Starter loses track of what's happening and, if it's good, shuts down to protect itself. Cheaper ones just blow the SCRs.

You can try adding a reactor in front of the soft starter, the added inductance in the incoming supply may soften that capacitor charging current rise time as far as what the SCRs see. That will of course drop your throughput efficiency as well, but may be your only option. If you can, borrow a suitable transformer somewhere that can be configured 1:1 and temporarily hook it up to see if it helps. If it does, the reactor will work too and they tend to be cheaper than transformers.
 

Rsteenson

Member
Thank you.

Thank you.

There are very few soft starters that are going to tolerate being fed from a rotary phase converter. Although the capacitors on the RPC will make the voltage APPEAR normal on a meter, and the differences are not as big a deal directly on an induction load like a motor, a soft starter has to deal with things like current rise times etc. The charging current of a capacitor has a very steep wave front as far as the SCRs are concerns, much the same as a dead short. What can happen is that the high dV/dt (change in voltage over change in time) can cause SCRs to "self commutate" meaning they fire on their own, i.e. when you don't necessarily want them to. Once SCRs begin firing at the wrong time, the Soft Starter loses track of what's happening and, if it's good, shuts down to protect itself. Cheaper ones just blow the SCRs.

You can try adding a reactor in front of the soft starter, the added inductance in the incoming supply may soften that capacitor charging current rise time as far as what the SCRs see. That will of course drop your throughput efficiency as well, but may be your only option. If you can, borrow a suitable transformer somewhere that can be configured 1:1 and temporarily hook it up to see if it helps. If it does, the reactor will work too and they tend to be cheaper than transformers.

Thanks for the insight. I am assuming I would see the same problems on a VFD? What do you suppose the chances are that a Line reactor would do the trick?
 

Jraef

Moderator, OTD
Staff member
Location
San Francisco Bay Area, CA, USA
Occupation
Electrical Engineer
Thanks for the insight. I am assuming I would see the same problems on a VFD? What do you suppose the chances are that a Line reactor would do the trick?
No you wouldn't see the same problem on a VFD, in fact a VFD can even act AS the phase converter (with lots of caveats).

I'd give the reactor about a 50-50 chance mostly because I'm not a big fan of the Telemecanique soft starters. I've had my share of trouble with them and have avoided using them for years. But I know lot's of people who think their fine, so I won't bad mouth them any more.
 

wjarrettc

New member
Hello. I'm an employee of Schneider Electric but I am NOT an expert on drives/soft-starter applications. However, I forwarded your post to one of our experts and received the following response:

Here are some notes from engineering on the ATS48 soft starts, the same would apply to ATS22 soft starts.

If a customer is using a rotary converter to go from single phase to three phase will an Altistart 48 work to feed a 460V water pump at 30HP?

We do not recommend using a rotary phase converter with our soft starts, because the soft start will see the phase imbalances and cause problems.

Another solution would be to use a drive as the phase converter to feed the motor. In order to do that, you need to oversize it. Basically, you take the motor full load amps X the square root of three and pick the corresponding drive HP. A line reactor is recommended and you need to turn the input phase loss off on the drive. Hope this helps.

You can also call 888-SQUARED for support if you have further questions. Thank you for choosing our products.
 
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