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Contactor Overload Relays on 2 phases

Joined
Jan 15, 2005
Location
The Netherlands
I have a contactor overload relay Telemecanique LR2 D13 1.6 to 2.5 Amp
It is protecting a 220 V 2Ph circuit board to drive a DC motor
We measure a load of 1.8 amps with a clamp on At least clearly below 2 amps
But setting the device at 2 amps it still trips after some time

That might indicate a bad device
Orrrrr
Does it only work properly with 3 ph connected ???
Reason I doubt is this line on RS online for a Schneider equivalent

This range of mini thermal overload relays feature compensated and phase failure sensitivity,
The phase failure sensitivity makes me wonder

As a solution we will try to put 2 heaters in serie to see if that works

Peter
 

TDegenhart

Diamond
Joined
Mar 26, 2011
Location
Geneva Illinois USA
Phase loss construction of the OL could be your problem. Since you only need two poles, route one leg back through the third OL pole so that the OL sees current on all three legs.


Tom
 

J_R_Thiele

Stainless
Joined
Jan 22, 2003
Location
Columbia Missouri
OK, I will jump in and display my ignorance.

I looked up D/C motor inrush current, and found that this was several times the running current.

I looked up the overload relay, and it appears to be a thermal device.

You say the device trips "after some time". Is that with the motor under constant load, or is the motor stopping and starting? Any chance something on the motor end that increases its load to an overload after it has run a while?

Is there ventilation where the relay is located?
 

TDegenhart

Diamond
Joined
Mar 26, 2011
Location
Geneva Illinois USA
Where do you measure the current, a transformer style clamp ammeter will not respond to DC. If there is AC on the DC you will only see the AC component unless you have a ammeter with a Hall Effect sensor in it. Alternately, use an oscilloscope to see what is there. You can also check the current with a shunt and read the true RMS voltage to get the current.

Tom
 

TDegenhart

Diamond
Joined
Mar 26, 2011
Location
Geneva Illinois USA
All I can say is check the calibration of the ammeter and if it is accurate, then the only other possibility besides a defect relay is if the OL is in a high ambient environment.

Tom
 
Joined
Jan 15, 2005
Location
The Netherlands
We put the 2 heaters in serie and tested again After a much longer time as before it tripped once more
So it did have some effect at least
But.....
After further inspection we discovered that it was actualy set on 1.75 amps insted of the 2 we assumed The 2amp mark was lined up with another feature on the device :D
 

rons

Diamond
Joined
Mar 5, 2009
Location
California, USA
I have a contactor overload relay Telemecanique LR2 D13 1.6 to 2.5 Amp
It is protecting a 220 V 2Ph circuit board to drive a DC motor
We measure a load of 1.8 amps with a clamp on At least clearly below 2 amps
But setting the device at 2 amps it still trips after some time

Those rotary dials are not that accurate. And your meter is displaying averages not peak values.

If the trip happens after some time than it would not be because of phase loss. Your dial is set
too close to the line. Bump it up a bit on the adjustment dial and be happy the thing is trying to work for you.
 








 
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