Re: Electrical Help three phase motor starters

Posted by NCWayne on August 28, 2014 at 22:12:43 from (173.188.169.54):

In Reply to: Electrical Help three phase motor starters posted by Stephen Newell on August 28, 2014 at 16:48:03:

It looks wrong to me because of the way the stop button is wired. If L1 is hard wired to one side of the coil on each contactor, then you have a 220V coil. That being the case you need to energize the other side of the coil in order to operate the contactor. This will be done with L2 using a start button for each motor so they can be started one at a time. Now, using the push button design you've got pictured with two start buttons, but only one stop button you've got to break the other side (L1) to cut power to both of the the coils at the same time and stop both motors together.

That said I am assuming that each of the starters has an aux contactor in addition to the three main contactors? If not your screwed and can"t do what your wanting to do. Now if the break in the light blue lines are aux contactors on each starter, here's what you need to do.

First take the hard wired connection from L1 and remove it from each of the coils. Now wire each of the coils back to L1 but this time running the one leg from both of them through the stop button. In essence this gives you a NC circuit between L1 and the coils just like you've got now, but with the ability to now open that circuit by pushing the stop button.

Now take a wire from L2 and run it to the common side of each of the start buttons. From the switched side of the start buttons run wires to each of the aux contactors---through them----and then on to the second post on the coil of the starter they are connected to. Do this on both starters.

Now run another individual wire from the switched sides of each start button to same post on the coils you hooked the wires from the aux contactors to. Basically this gives you the ability to push the start button and in closing that switch, to power the coil, to pull in the starter. When it pulls in the aux contactor will also pull in and close. From this point the power is flowing through the aux contactor and it's now supplying power to the coil, not the start switch. This allows the coil to remain energized even when you release the start button and break that part of the circuit.

With that in mind the circuit is now energized with power flowing through the aux contactors to keep both coils energized. With separate start buttons, and separate aux contactors you effectively have two distinct circuits so you can start each motor separately from the other. Now you need to shut them both off together. To do that all you've got to do is break the other wire going to each coil. That is where changing the way L1 is connected comes into play. There is no way to break either of the L2's powering the coil using just one stop switch. If you tried to do that, upon startup, the voltage would back feed at the stop switch and both contactors would pull in every time one start button was pushed. In other words both motors would start at the same time and that's not what you want. So, to enable starting the motors individually and stopping them together, you've got to break the "other" wire, or L1.

Basically the setup is this. The coil needs both L1 and L2 to become energized. Remove either one and the switch opens. So L1 power is maintained to both coils as long as the stop button isn't pushed in. L2 power then goes through either start switch when it's pushed causing the contactors to pull in. When they pull in they both connect the main contactors to power the motor, as well as the aux contactors to power the coils off of L2. As long as both sides of the the coils stay energized the coils stay pulled in. Now push the stop button and you denergize the L1 side of the coil, causing the contacts to open. This in turn opens the aux contact and breaks the L2 circuit until one of the start buttons is pushed again.

I wish I knew how to post drawings as it's a lot easier for me to draw than to explain.

The way I am seeing what you've got drawn pushing the stop button will do nothing but cut power going to the common side of the start switches, which will accomplish nothing. I say that because once the start button is pushed and the aux contactor pulls in, there is no power needed to the start buttons to keep the coil energized because the power is now flowing through the aux contacts, and the only way to break the circuit, to stop both motors with one button, is to break the common L1 connection to both coils instead of the individual L2 connections.

Again this is hard as heck for me to try to explain but I know what I am seeing in your drawing isn't going to work like you want it to.....if I am understanding everything you"ve got pictured right.

Replies:

• Re: Electrical Help three phase motor starters Stephen Newell 05:29:23 08/29/14 (0)

Add a Reply Name: E-Mail: Subject: Comments: Optional Link URL: Link Title: Optional Image URL: Optional Video Title: Optional Video URL: Advanced Posting Options Email Notification: If you check this box, email will be sent to you whenever someone replies to this message. Your email address must be entered above to receive notification. This notification will be cancelled automatically after 2 weeks.   Advanced Posting Tools   Upload Photo  Select Gallery Photo  Attach Serial # List  Return to Post

TRACTOR PARTS	TRACTOR MANUALS

We sell tractor parts!  We have the parts you need to repair your tractor - the right parts. Our low prices and years of research make us your best choice when you need parts. Shop Online Today. [ About Us ]