Siemens motor starter

[Guest]

I have a problem with a new Siemens motor starter. It is suppose to be starting a 10 hp 3 phase weg motor. When I push the start button, the coil engages but nothing else happens. I wired it the way the Tech from Siemens told me to but I have a feeling it is wrong. A put a meter on the 3 terminals of the start-common-stop switch and the start-common-stop all had 120-208 volts to them. I don't know a lot about motor starters but I thought the stop terminal is the only one that should have voltage, not all 3. I also put a meter on the load side of the starter to the motor after the start switch was engaged and there was no power there.

I hope someone can help with this problem.

Thanks,

Doug

[Guest]

If the coil is engaging when you hit the start button, but no power is getting to the load side terminals, your problem has nothing to do with the start/stop circuit. Since is is obvious from the wording of your question that you are somewhat new to this, let's start at the basics.

 

1) Are you sure that you have line power on the "L" side (L1, L2, L3) of the contactor? If not, there is your problem. I'm not trying to be a smart ass, I am just not taking anything for granted here.

 

2) Are you sure that there is not another safety disconnect somewhere downstream from the starter that is open? I doubt this one because if it were, you would still read voltage on the load side of the contactor when it is on, but let's just cover all of the bases.

 

3) When you say that "the coil engages" does that mean that you can see the plunger of the contactor being pulled in? If not, what did you mean by that?

 

4) If it does pull in, turn off power and remove the power conductors. Take your meter and put it in Ohm check or Diode check mode. Manually push the plunger in and check continuity from L to T on each phase. Did you have continuity? If not, for some reason you have a contactor with no contacts! It has happened to me once before. The contactor had come from a distributor's shelf, but someone had used it to rob a set of replacement contacts and returned it to the distributor without telling them.

 

If you do have continuity, then you were mistaken about one of the other issues above, because if the contacts are closing when the plunger is in, and the plunger pulls in when the start button is pressed, and the line voltage is present when this happens, then you should have voltage on the load side of the contactor when you press the start button.

 

If not, welcome to "The Twilight Zone!"

[jraef]

Woops, forgot to log in before answering. That was from me :-p

[Guest]

I have a siemens star delta control circuit for a 75 KW motor .

my question is IF i modified this star delta control and let the motor start in Direct on line , is there a risk doing this ????

please advice ?