Motor protection relays — automatic protection of fan motors against overload and supply faults

Protection relays sit between a working motor and a burnt-out motor — an investment of a few hundred lei protecting a motor worth several thousand. They automatically detect abnormal operating conditions and disconnect the motor before damage becomes irreversible. Overload (thermal) protection: motor draws more current than nominal — most commonly from a clogged filter (increased hydraulic resistance overloads the motor), partially blocked rotor or excessive ambient temperature. Adjustable to the motor's nominal current. Phase failure protection: for three-phase motors — loss of one of 3 phases causes overload on the other two and rapid motor burnout. Asymmetric operation protection: unbalanced three-phase voltages produce excessive vibration and premature bearing wear. Mandatory for any three-phase fan motor without integrated thermal protection.