Contactor chatter?

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D a n

Member
Location
WI
Recently installed a current sensing relay. The contactor that the current sensor controlls has a 24 volt coil. The current sensor seems to let a small amount of voltage through even when the contacts aren't closed. Which in turn is causing contactor chatter. There must be a filter or shorting method I can use? Any guidance would be great. Thanks:ashamed1:
 

Smart $

Esteemed Member
Location
Ohio
Recently installed a current sensing relay. The contactor that the current sensor controlls has a 24 volt coil. The current sensor seems to let a small amount of voltage through even when the contacts aren't closed. Which in turn is causing contactor chatter. There must be a filter or shorting method I can use? Any guidance would be great. Thanks:ashamed1:
Welcome... :thumbsup:

Sometimes a "snubber" can be installed to eliminate the chatter. Can you provide make & model of the circuit components, or better yet, a link (URL) to the data sheets?
 

Jraef

Moderator, OTD
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Electrical Engineer
Welcome... :thumbsup:

Sometimes a "snubber" can be installed to eliminate the chatter. Can you provide make & model of the circuit components, or better yet, a link (URL) to the data sheets?
What he is referring to is that more than likely the "contacts" on your current sensing relay are not really contacts, but a triac (solid state switch), which has leakage. But honestly, leakage through a triac is not usually enough energy to make a contactor coil chatter. Is it by chance also one of the new "electronic" contactor coils? Those can be extra sensitive because in some forms, they have their own little triac inside as an amplifier and then use the line power itself to energize the magnet. On some, you may not even be aware of it because all of the connections are internal to the contactor.

So like he said, details would be helpful.
 

D a n

Member
Location
WI
http://controlscentral.com/Portals/0/data_sheets/RIBXG_SERIES.pdf Here is the current relay still trying to come up with contactor sheet. It is just a general purpose contactor. I beleive i might have to come up with a different method to turn the contactor on and off. What I am trying to do is turn a booster fan on that is down stream from a Jen aire cooktop. The home owner buried the cooktop so there is no way to get at it. Which really doesn't matter because it wouldn't have contacts anyways. My problem is the current of the jen aire fan is about .6 amps and when a burner comes on it goes up quite a bit. the current sensor i used is the gta. Thanks
 

gar

Senior Member
Location
Ann Arbor, Michigan
Occupation
EE
150106-2110 EST

Dan:

Get a 100 ohm 1/2 or 1 W resistor. Higher wattage is OK. Put the resistor in series with the contactor coil. Don't energize the coil. Measure the voltage across the resistor. A 1 V reading is a leakage current of 10 mA, and a power dissipation of (0.01^2)*100 = 0.01 W in the current measuring resistor. At 10 V across the resistor the current is 100 mA, and power of 1 W. Report back your leakage current.

Note: 100 mA will burn up the resistor if it is rated at 1/2 W.

.
 

Jraef

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Staff member
Location
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http://controlscentral.com/Portals/0/data_sheets/RIBXG_SERIES.pdf Here is the current relay still trying to come up with contactor sheet. It is just a general purpose contactor. I beleive i might have to come up with a different method to turn the contactor on and off. What I am trying to do is turn a booster fan on that is down stream from a Jen aire cooktop. The home owner buried the cooktop so there is no way to get at it. Which really doesn't matter because it wouldn't have contacts anyways. My problem is the current of the jen aire fan is about .6 amps and when a burner comes on it goes up quite a bit. the current sensor i used is the gta. Thanks

Sensor Output:
? Solid State Contact
? 30 Vac/dc, .4 Amp Max.
? When current sensor status is off (open), leakage
<30 uA @ 30Vac/dc

Note: 0.4A maximum on that triac! That's 9.6W at 24VDC, the smallest DC contactor coil rating I could find was 36W inrush. it might be that you are frying that little contact on the CSR and it is shutting itself off to protect itself, then immediately turning back on. You would need to have that little CSR operate a tiny little ice cube relay, then have that relay operate the contactor coil.

Or just get a real CSR that has real contacts on it.
 

gar

Senior Member
Location
Ann Arbor, Michigan
Occupation
EE
150106-2420 EST

The solid state relay, if it is one, can not be a Triac because it has an AC and DC capability.

Does the contactor chatter when it is not supposed to be energized, or is the chatter when the contactor is energized?

What does the contactor do when the signal circuit to the contactor coil is completely open?

Dan you need to use some simple troubleshooting procedures to find the origin of your chatter.

.
 

D a n

Member
Location
WI
does have both AC/DC capability. The Voltage is coming through even when the contacts on the current sensor are open. I'm getting 11-12 volts at all times. The contactor wants to chatter all the time. I can't find any ratings on the coil of the contactor but can't believe it draws more than .4 amps. Contactor is a ac contactor. Was thinking about just ordering a 120 volt csr with contacts on it but where i live it will be extra time to get. for service purposes I was trying to stick with material that my supplier stocks. My biggest question is that when they turn a burner on with the cooktop will the coil sensor shut off?That is why a ordered one between .75-150amp rating I assumed it was adjustable to turned on but didn't realize that it also shuts off (it has ranges)
 
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dfmischler

Senior Member
Location
Western NY
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Facilities Manager
The Voltage is coming through even when the contacts on the current sensor are open. I'm getting 11-12 volts at all times.
Did you try measuring the voltage across a resistor in series with the contactor coil as gar suggested? That would tell you how much leakage current is getting through your current sensing relay, and help to suggest a course of action. The output of the CSR may already be fried, or something else may be wrong. I don't think the 30uA of leakage expected from the spec would make the contactor chatter.
 

D a n

Member
Location
WI
Did you try measuring the voltage across a resistor in series with the contactor coil as gar suggested? That would tell you how much leakage current is getting through your current sensing relay, and help to suggest a course of action. The output of the CSR may already be fried, or something else may be wrong. I don't think the 30uA of leakage expected from the spec would make the contactor chatter.




Will try that when I get there next Thanks.
 

gar

Senior Member
Location
Ann Arbor, Michigan
Occupation
EE
150107-0827 EST

Reading this thread again there are inconsistencies, and incomplete information.

Is the contactor coil AC or DC (exclusive or), or AC-DC (inclusive or)? If the proper type of excitation (AC or DC) is applied, then at what voltages does the contactor pull-in, and drop-out? In what voltage range of the proper excitation type at the contactor coil input does contact chatter occur?

The current sensor defines a threshold current that is automatically set. This is an incorrect usage of the word threshold. A more correct word is set-point.

The current sensor has a sensing band +/- a percentage of the set-point for which its output contact is closed. Below the lower limit the sensors output is open, and above the upper limit the output is also open. Further at each of these limits there is hysteresis.

From the specifications for the current sensor it is likely that an FET is the switching element. It is not a latching device (SCR or Triac) or it could not switch DC. The leakage current specification implies no internal snubber. The leakage current specification is so low that it should not be a problem. So does the chatter really occur when the current sensor output is off?

What does chatter mean? The on-off nature of the cooktop fan in combination with the characteristics of the current sensor may produce an oscillator.

Jraef's comment on coil power in relation to the current sensor output specification is something that must be considered. Has the current sensor been damaged?

.
 

gar

Senior Member
Location
Ann Arbor, Michigan
Occupation
EE
150107-0908 EST

Dan:

The reason for using a 100 ohm, or some other value to measure leakage current is that this saves the cost of replacing the meter fuse, like $15 for Fluke, if you have a high high and unexpected current. Small resistors are cheap at a few cents each. The choice of resistance value is a function of expected leakage current.

If your measured output voltage was 10 V or so, then was this with no load on the current sensor output? A high impedance meter input is typically in the 10 Megohm range. One microampere thru 10 megs is 10 V.

With no current thru your sensor load the output with 10,000 ohms. What is the voltage across the 10,000 ohm resistor? One microamp should be 0.01 V.

Also use your DVM to measure the contactor coil resistance. Can you see a shading coil (copper slug on part of the contactor pole piece)? Search Google for --- shading coil contactor photos.

.
 

Smart $

Esteemed Member
Location
Ohio
Maybe use one of these. Woodworkers use these to auto run dust collectors when they start up a tool. These are 120V but
adapting it to other uses shouldn't be too tough.

http://www.woodcraft.com/Product/149950/ivac-automated-shop-vacuum-switch.aspx
There are plenty others out there suitable for 120V load from the get go, e.g. ...

https://www.google.com/shopping/product/2564237493572220482?q=current+sensing+relay+120v

https://www.google.com/shopping/product/9246217935781086228?q=current+sensing+relay+120v

I realize OP wanted to stay with parts available at local supply house, but... :happysad:
 
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