MOV
MOV turns up in 2 fields: valves, electronics. Here is what it means to the people in each one.
MOV in valves
Motor-operated valve: a valve driven by an electric actuator with a motor, gearbox, torque switch and limit switches.
Motor-operated valve. The actuator drives through a worm gear, stops on a limit switch at a set position or on a torque switch when output torque reaches a set value, and has a handwheel with a declutch lever for manual use. MOVs dominate large gate and butterfly valves in water, power and pipeline service, where thrust needs are high or there is no instrument air. Nuclear plants test them closely for thrust margin.
"MOV on the intake tripped on torque halfway closed, something's in the gate, send a crew with a handwheel and a flashlight."
MOV in electronics
A metal-oxide varistor is a voltage-dependent resistor used to protect circuits from voltage spikes.
A metal-oxide varistor is a discrete electronic component whose electrical resistance decreases rapidly as the voltage across it increases. Placed in parallel with the circuit it protects, it remains highly resistive during normal operation but becomes highly conductive during a transient voltage surge, shunting the excess current safely away. They degrade slightly with every surge they absorb and eventually fail, often dramatically.
"The surge protector stopped working because the primary MOV sacrificed itself during that lightning strike."