Motor protection relay testing.

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Old 11-13-19, 07:55 PM
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Motor protection relay testing.

So I have a motor protection relay which has 2 pairs of contacts, a normally open pair and a normally closed. When it trips I want the NC switch to open and cut the power and the NO switch to close and light a lamp and sound a buzzer.

So I just wired everything up and turned on the power. When I press the test button on the relay, it does interrupt the power to the contactor, what doesnít happen is the other part, the light doesnít go on. To make sure the lamp was good and the alarm worked I bridged the NO terminals with a wire and sure enough everything turned on.

which leaves me wondering, is the relay bad or does the test button only operate the NC switch and is there a way to find out?
 
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Old 11-13-19, 09:24 PM
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The NO contact could be bad or you could have it wired wrong.
Can you post the wiring drawing of what you have.
 
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Old 11-14-19, 06:02 AM
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A relay's contact designation refers to the contacts condition with its coil is de-energized. In your scenario the motor relay coil is energized when something else is tripped. What is driving the motor relay coil?
 

Last edited by beelzebob; 11-14-19 at 06:03 AM. Reason: submitted before complete
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Old 11-14-19, 09:44 AM
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A video might be easier to follow than my amateur wiring design .

in the video I first press the test button to show that that does indeed interrupt the circuit but doesnít light the lamps or activate the alarm relay. Then after some fumbling with the multimeter, I bridge the NO contacts to show what should happen.

https://photos.app.goo.gl/8X2sSWZps8M1EmCz9
 
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Old 11-14-19, 10:36 AM
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-removed this text-

Verify you are (or are not) using the built-in aux contacts for ON/OFF control. Look at this schematic: https://temcoindustrial.com/product-...verload-relays

Also, the NC contact is driven by the heaters, not the main coil... It's function is to open when the heater opens, and then killing the contactor coil current.
The NO contact is driven by the coil.
 

Last edited by telecom guy; 11-14-19 at 10:53 AM.
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Old 11-14-19, 10:38 AM
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If bridging the contacts makes it work then the contacts are bad.
 
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Old 11-14-19, 12:37 PM
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Telecomguy,

In the link you posted looks like the push button control is wired through the contactor not the overload that is not the setup Iím using. In the picture (not the schematic) on that link you can see there are 4 screw terminals. 95, 96, 97 , 98

im using terminals 95 & 96 which are the normally closed contacts from the 24v+ side. That seems to work fine, as you can see in the video when I push the test button, the contactor coil is deenergizdd as should be. The issue is, as I understood it, the auxiliary NO contacts 97, 98 should close when the relay trips, but when I push the button they donít. Iím not sure if that is a product of a broken relay or if the test button is not designed to close those contacts. As you can see in the video, I have two and neither works.
 
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Old 11-14-19, 01:09 PM
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can you post a link to the relay/overload you are working with?

I suspect the 90 series contacts do not move with the contactor; only the heater.
 
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Old 11-14-19, 06:04 PM
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Ok, I feel dumb, but problem solved.

that button I was pushing in the video? Not the test button! Thatís the reset button. Once I found the actual test button (small transparent sliding switch on the top side of the relay) everything works exactly as expected
 
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