Motor Auxiliary Contact Question

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I have a motor control system that uses a auxiliary contact to energize a relay coil that in turn energizes the solenoid to operate a damper. The motor starter is a Cutler-Hammer AN16SN0 starter. Based on initial troubleshooting it appears that the auxiliary contact is not closing instantaneous once the coil is energized. It takes several seconds to close, and the time has increased. I am use to a aux contact opening during operation after closing, such as a seal-in, especially on AB starters, but haven't experienced a aux contact closing slowly. As anyone else experienced this problem, is this a common problem on this type of starter, or something else? Appreciate the help.
 

Saturn_Europa

Senior Member
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Fishing Industry
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Electrician Limited License NC
I'd unwire the circuit from the aux contact and ohm out the aux contact while cycling the starter off and on. It's a mechanical set of contacts and should actuate any time the starter pulls in. One or two seconds is an eternity........

If possible an kill the breaker for the load and leave control power on, that way you don't short cycle the motor off and on

Why do you think it is taking a few seconds to actuate?

Have you tried tightening all the terminals?
 

Ingenieur

Senior Member
Location
Earth
are you sure that it's not the damper actuator that is appearing to slow down the loop?
and the contacts are operating properly?
 

rlundsrud

Senior Member
Location
chicago, il, USA
What I would recommend is using the initiating circuit to operate the damper and then an end switch from the damper will start the motor starter. This guarantees that the motor doesn't start until the damper is fully opened.
 

Little Bill

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I've taken apart several relays/starters. One side of the aux contacts move with the main contactor via the housing & solenoid. Unless there is something bent on the arm of the contact it should pull in immediately and make contact or break, depending on whether it's a NO or NC contact.

If the main contacts are pulling in all the way then so should the aux contacts. My vote would be the damper is hesitating.
 
I have a motor control system that uses a auxiliary contact to energize a relay coil that in turn energizes the solenoid to operate a damper. The motor starter is a Cutler-Hammer AN16SN0 starter. Based on initial troubleshooting it appears that the auxiliary contact is not closing instantaneous once the coil is energized. It takes several seconds to close, and the time has increased. I am use to a aux contact opening during operation after closing, such as a seal-in, especially on AB starters, but haven't experienced a aux contact closing slowly. As anyone else experienced this problem, is this a common problem on this type of starter, or something else? Appreciate the help.

For additional info the aux contact actually energizes a relay. This relay has a contact that activates a running light and sends power to the solenoid for the damper. My first thought was that the relay was malfunctioning, so I replaced the relay. The starter has 2 NO aux contacts. One is used, and the other is not. I checked the unused aux contact and it does not read close when the starter coil is pulled in. The used aux contact does close show close, however it takes awhile to close. I am thinking a may have something with the starter internal mechanism pulling in the aux contacts. Any thoughts?
 
I've taken apart several relays/starters. One side of the aux contacts move with the main contactor via the housing & solenoid. Unless there is something bent on the arm of the contact it should pull in immediately and make contact or break, depending on whether it's a NO or NC contact.

If the main contacts are pulling in all the way then so should the aux contacts. My vote would be the damper is hesitating.

The aux contacts activate a relay that closes a contact that powers the solenoid. So the damper is not hesitating.
 

ActionDave

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For additional info the aux contact actually energizes a relay. This relay has a contact that activates a running light and sends power to the solenoid for the damper. My first thought was that the relay was malfunctioning, so I replaced the relay. The starter has 2 NO aux contacts. One is used, and the other is not. I checked the unused aux contact and it does not read close when the starter coil is pulled in. The used aux contact does close show close, however it takes awhile to close. I am thinking a may have something with the starter internal mechanism pulling in the aux contacts. Any thoughts?

The aux contacts should close immediately when the coil is energized.

Is this a NEMA contactor or an IEC?
 

Jraef

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So that appears to be a NEMA size 5 Freedom series starter. One thing I’ve seen is that the aux contacts for size 3-5 are different from those for Size 0-2, but sometimes people don’t know that and try to force them to work and that never goes well. Check the part numbers carefully. The difference is subtle, I believe the contacts for larger starters have an extra “1” at the end of the string. If you do have the correct one, it’s likely burning out and the high resistance causes a delay as it heats up, then makes better contact. That will only get worse, change it out immediately.

It should also be noted that C-H offers a side mount TIMER that looks similar to an aux contact. Again, check the part number of the auxiliary device.
 

Ingenieur

Senior Member
Location
Earth
that is a big starter, fan I assume
the failure of the damper to open or open fast enough can be bad

I agree
use start command to open damper
and a damper position switch to start the fan
 
Motor Auxiliary Contact Question

So that appears to be a NEMA size 5 Freedom series starter. One thing I’ve seen is that the aux contacts for size 3-5 are different from those for Size 0-2, but sometimes people don’t know that and try to force them to work and that never goes well. Check the part numbers carefully. The difference is subtle, I believe the contacts for larger starters have an extra “1” at the end of the string. If you do have the correct one, it’s likely burning out and the high resistance causes a delay as it heats up, then makes better contact. That will only get worse, change it out immediately.

It should also be noted that C-H offers a side mount TIMER that looks similar to an aux contact. Again, check the part number of the auxiliary device.

The aux contact part number is C320KGS20, which I verified the other day. The motor starter is a C-H NEMA size 5 starter series B1, and the part number on the starter in the field is AN16SN0. I have ordered the starter and contact blocks. I am curious why would high resistance cause the delay with the aux contacts closing. The main contacts close immediately, but the aux contacts take time, which has increased. Thanks for any help.
 

Jraef

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That should be the correct set of contacts.

Aux contacts will get a build-up "crud" on the contact surfaces when contaminants in the surrounding air get into the contact chamber. Load switching and arcing will usually burn that off, but without that arcing it just gets worse and worse. Then when the resistance increases, it becomes like a heater and heats up, EVENTUALLY burning enough off to allow better conduction. That burn-through process looks like a time delay. In this case because you are only switching a small relay, the load on those contacts is probably so light that this is happening.

Some manufacturers built in a "wiping action" in the way the contacts close against each other to prevent this, but I know from experience (with elevator controls where this is a big problem*) that the C-H side mounted aux contacts don't have that wiping action (Siemens too). This is especially bad on machinery where there ends up being a lot of vaporized oil and/or coolant in the air (hence the issue with elevators). They do have it on their top mounted aux contacts, but on Size 3 and up they don't offer the top mounted aux. The only viable solution I found was to just change out the aux contacts periodically, or instead of going through that aux. relay, just switch whatever the load is directly.

* The reason I know this is because I once got paid to do an in-depth study of why aux. contacts on Siemens starters kept failing in the elevator industry. It was happening on Siemens and C-H, but not other brands. Of the brands this one company used, those two did not have a wiping action, and on C-H, that was only on the side mounted aux contacts, which they only used on Size 3 and 4.
 
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That should be the correct set of contacts.

Aux contacts will get a build-up "crud" on the contact surfaces when contaminants in the surrounding air get into the contact chamber. Load switching and arcing will usually burn that off, but without that arcing it just gets worse and worse. Then when the resistance increases, it becomes like a heater and heats up, EVENTUALLY burning enough off to allow better conduction. That burn-through process looks like a time delay. In this case because you are only switching a small relay, the load on those contacts is probably so light that this is happening.

Some manufacturers built in a "wiping action" in the way the contacts close against each other to prevent this, but I know from experience (with elevator controls where this is a big problem*) that the C-H side mounted aux contacts don't have that wiping action (Siemens too). This is especially bad on machinery where there ends up being a lot of vaporized oil and/or coolant in the air (hence the issue with elevators). They do have it on their top mounted aux contacts, but on Size 3 and up they don't offer the top mounted aux. The only viable solution I found was to just change out the aux contacts periodically, or instead of going through that aux. relay, just switch whatever the load is directly.

* The reason I know this is because I once got paid to do an in-depth study of why aux. contacts on Siemens starters kept failing in the elevator industry. It was happening on Siemens and C-H, but not other brands. Of the brands this one company used, those two did not have a wiping action, and on C-H, that was only on the side mounted aux contacts, which they only used on Size 3 and 4.

So do you think that only my aux contacts are bad, and the starter is okay. Due to the importance of this fan system it is difficult to perform normal troubleshooting activities. I am planning on replacing both the aux contacts and motor starter, since I can't verify there is something wrong with the mechanical system (i.e. the plunger mechanism closing the aux contacts). Like I have stated earlier, I'm use to A-B and Square D aux contacts failing open either permanently or after closing initially and then opening. Your explanation does explain why it has took time for the aux contacts to close. In my facility I have very few C-H starters, so this is something new to me. Thanks for your help!
 

Jraef

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I doubt it's anything in the starter itself, that main contactor armature mechanism is just brute force and the way it acts on the aux contacts is basically a direct drive off of the same armature. So if the aux contacts were 'squishy' you would see it in the main contacts as well. Aux contacts are designed to mechanically operate slightly ahead of the main contacts, it's pretty tough to mess with the mechanics involved.
 
I doubt it's anything in the starter itself, that main contactor armature mechanism is just brute force and the way it acts on the aux contacts is basically a direct drive off of the same armature. So if the aux contacts were 'squishy' you would see it in the main contacts as well. Aux contacts are designed to mechanically operate slightly ahead of the main contacts, it's pretty tough to mess with the mechanics involved.

Thanks for your help. I replaced the starter ,with new aux contacts, just as a preliminary task. Everything worked exactly as designed. I feel confident it was the aux contacts. I am also going to replace the aux contacts on my other fan. Again, thanks for your help.
 
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