I am having a problem powering a Fan from a control transformer.

The design uses a transformer meant to step down from 240V to 24V. A previous engineer decided to run the 240 to the primary and then use the center tap of the primary to get 120V. So the secondary is not used but the primary is being used. When enrgized this is working. I measure 240-250V range from L1 to L2 and 130V out of the Center Tap. My problem is once I connect a Fan to it i only see 80V from center tap to L1 which is the circuit the Fan is on and the fan is running at a very low speed, but 180V to L2. I feel this is abnormal but is the load from the fan causing the voltage to become that unbalanced? Anyone have an idea on what is causing this or what i can do to stop it. I have already tried using a different fan and the signs are pointing to bad transformer but like i said, with no load it performs how it is intended.

 

Very small transformer and very large fan? Do you have pictures.

 

Very small transformer and very large fan? Do you have pictures.

It is a small fan, we have used this configuration for years and had no problem powering the fan in the past. It seems like a poor connection somewhere but I have checked all wires and found no issue, seems the transformer may be defective.

 

I would suspect your small fan is defective (usually bad bearings from long use) and is loading down the autotransformer with increased power draw to keep spinning at X speed. Try replacing the fan with a new one of the same type.

 

we have used this configuration for years and had no problem powering the fan in the past.

Replace the transformer.

 

Replace the transformer.

Replace the transformer by an autotransformer designed for the job.