offset
The steady state deviation of a controlled variable from a fixed setpoint. Also the control in a signal follower which is used to adjust the follower to respond to the minimum reference signal.

oscilloscope
An instrument that visually shows the pattern that represents variations in an electrical quantity.

open loop
A control system without feedback.

outlet temperature
see design outlet temperature

output contactor
An output contactor provides a selector switch and contactor in the drive enclosure that will electrically disconnect the drive from the motor. Contactor bypass includes this function.

output follower
A circuit which provides an analog output signal which corresponds to the driveís speed. It is often used for a remote speed indication.

overcurrent
An abnormal operating condition of an electronic drive that causes current in the drive to exceed the current limit setting. See current limit. This is typically caused by a short circuit, either internal or on the driveís output. The drive protects itself by shutting off the output.

overload
An abnormal system condition that demands more than design current. Run in this condition, the drive or motor overload will protect the system by shutting off the output.

overload capacity
The ability of the drive to withstand loads (currents) beyond the systemís continuous rating. It is normally specified as a percentage of full load current for a specified time period.

overload relay
A device for protecting a motor or other electrical device from an overload current or voltage.

overshoot
The amount that a controlled variable exceeds a desired value after a change in input.

overtemperature
An abnormal operating condition of an electronic drive that causes the internal temperature or the heatsink temperature to rise above safe levels. This can be caused by too high an ambient temperature, too high an elevation, defective cooling fan, blocked vents, etc. The drive will protect itself by sensing the temperature and shutting off the output.

overvoltage
An abnormal operating condition of an electronic drive that causes the internal voltage to rise above normal limits. This is usually caused by a high input line or by a regenerating load. The drive will protect itself by sensing the internal voltage and shutting off the output.