CONTROL TRANSFORMERS VOLTAGE DROP PROBLEM
CONTROL TRANSFORMERS VOLTAGE DROP PROBLEM
(OP)
We are using 440/24 V 50 VA in a 30 KW (2 steps) humidifiers.
When starting the second step the secondary voltage drops to about 13.5 Volts and the contactor couldnt close contacts and work properly.
Why could this be happening if we have measured the 440 V in the primary and the 24 Volts in the secondary with the first step (50% of the load)?
Thank you,
When starting the second step the secondary voltage drops to about 13.5 Volts and the contactor couldnt close contacts and work properly.
Why could this be happening if we have measured the 440 V in the primary and the 24 Volts in the secondary with the first step (50% of the load)?
Thank you,






RE: CONTROL TRANSFORMERS VOLTAGE DROP PROBLEM
You should measure the current being taken by the coils of the contactors.
UPS engineer http://www.powerups.co.uk
RE: CONTROL TRANSFORMERS VOLTAGE DROP PROBLEM
RE: CONTROL TRANSFORMERS VOLTAGE DROP PROBLEM
Try a simple ohm measurment from the chassis to ground to start. I am not familiar enough with humidifiers to offer any advice besides that...
RE: CONTROL TRANSFORMERS VOLTAGE DROP PROBLEM
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If we learn from our mistakes I'm getting a great education!
RE: CONTROL TRANSFORMERS VOLTAGE DROP PROBLEM
Alan
RE: CONTROL TRANSFORMERS VOLTAGE DROP PROBLEM
Either double or triple your existing transformer size or add a second one for the second contactor.
Keith Cress
kcress - http://www.flaminsystems.com
RE: CONTROL TRANSFORMERS VOLTAGE DROP PROBLEM
I used a formula that considers both values and the outcome is 40 VA´s that is why I picked a 50 VA transformer.
Are you telling me I should have selected something bigger than the 120 VA´s (inrush) of both contactors coils ?
RE: CONTROL TRANSFORMERS VOLTAGE DROP PROBLEM
13V demonstates excessive load on your supply, that's the secondary of your instrumentation transformer.
It could also be caused by a few other things. A bad connection between the transformer and the contactors. The wire could be too small. The switch could have bad contacts. Things of that nature.
Also you state you have 440V This is an "old voltage". If you have a 480V transformer and are feeding it 440V you are already down the curve of what your contactor's want.
Could also be the 40A inrush is a bunch of hooyee.
A 100VA is about $40US
My bet is your IT is way too small.
Keith Cress
kcress - http://www.flaminsystems.com
RE: CONTROL TRANSFORMERS VOLTAGE DROP PROBLEM
How far from the supply panel to the humidifier?
Bill
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"Why not the best?"
Jimmy Carter
RE: CONTROL TRANSFORMERS VOLTAGE DROP PROBLEM
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If we learn from our mistakes I'm getting a great education!
RE: CONTROL TRANSFORMERS VOLTAGE DROP PROBLEM
RE: CONTROL TRANSFORMERS VOLTAGE DROP PROBLEM
We just found and solved the problem.
The problem was not an undersized transformer, the voltage drop was coming from a wrong wire from the humidifier to the humidistat installed about 80 mts away from each other. This was done wrong by the field technician.
We solve this by installing a relay to repeat the signal from the humidistat so that the power didnt have to go through all these 90 mts and left the wire already in place.
After this the control voltage went steady again at 24 volts.
Best regards,
RE: CONTROL TRANSFORMERS VOLTAGE DROP PROBLEM
Alan
RE: CONTROL TRANSFORMERS VOLTAGE DROP PROBLEM
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If we learn from our mistakes I'm getting a great education!