What phenomenon should be avoided when using a control transformer in a circuit?

When utilizing a control transformer in a circuit, the phenomenon that should be avoided is back feed. Back feed occurs when unintended electrical energy flows back into the circuit from the load or connected devices, which can lead to various safety hazards and operational issues.

Control transformers are designed to step down voltage and provide isolation necessary for control circuits. If back feed occurs, it can compromise the isolation that the transformer provides, potentially damaging the transformer itself or other components in the control circuit. Additionally, back feed can create unsafe conditions for maintenance personnel or other electrical equipment connected downstream.

Therefore, preventing back feed is crucial for ensuring the safe operation and functionality of electric motor control systems.