A motor starter is basically a contactor with overloads. The overloads in the starter are selected according to both the voltage and the RLA of the compressor. These protectors respond to a change in heat caused by voltage drop and amperage increases. If the starter senses an overload condition in any one of the motor circuits, it will cause the contactor to open and interrupt the power to all the circuits. The starter will usually interrupt power before the motor’s internal overload opens. Motor starters are designed to be manually reset after they trip on overload. The assumption is that the person resetting the control will then monitor the motor operation to determine what caused the motor protection to open.