I have a 12VAC-controlled contactor (ESB 20-20, rated for 12V @50Hz), and a 220/12 transformer that I intend to connect to the contactor. Unfortunately, rather than 12V, the transformer outputs 14V (which is outside of the 85—110% range of allowed voltage). Which option should I employ?
- Put a resistive voltage divider between the transformer and the contactor?
- Use two opposite 12V Zener diodes to clip a half-wave each?
- Return the transformer to the shop and try to find a more precise one?
- Throw out both the transformer and the contactor, buy a DC-driven contactor and a stabilized power supply?
- Stop caring, connect them as they are?
Edit: forgot to add, while 14V is the measure of an unloaded transformer, under the contactor load the transformer voltage drops an insignificant amount, to around 13.8V.
Best Answer
If you measure the transformer output voltage without load, this value can be higher than the nominal value. You must measure with the maximum load that the transformer support; this is the voltage that you must take care of.
For the contactor, I think that you can connect it, and measure the voltage on the coil when the device is operating, to verify that the voltage applied is safe.