Motor Controls Ch 19

Solder Pot

A device using a low-melting solder and an overload heater sized for the amperage of the motor it is protecting. The solder will melt, opening the circuit when there is an overload. It can reset.

Motor Service Factor

A factor above an electric motor's normal operating design parameters, indicated on the nameplate, under which it can operate.

National Electric Code "NEC"

A publication that sets the standards for all electrical installations, including motor overload protection.

Manual Reset

A safety control that must be reset by a person, as opposed to automatically reset, to call attention to the problem.

Relay

A small electromagnetic device to control a switch, motor, or valve.

Pilot Duty Relay

A small relay that is used in control circuits for switching purposes. It is small and cannot take a lot of current flow, such as to start a motor.

Contactor

A switch usually magnetically operated, which is used to open and close an electrical circuit. A larger version of the relay. It can be repaired or rebuilt and has movable and stationary contacts.

Magnetic Overload

An overload device that senses the current draw of a load by the magnetic field produced, which is proportional to the current draw. The device will open a set of contacts on high current draws and allow them to close when the ampere draw returns to normal.

Motor Starters

Electromagnetic contactors that contain motor protection and are used for switching electric motors on and off.

External Motor Protection

Motor overload protection that is mounted on the outside of the motor.

Flame Sensor

The flame sensor sends an electrical signal to a central controller. This central controller operates the gas or fuel valves for releasing the combustible materials into the burning chamber of the furnace or boiler. Upon an initial signal, the flame sensor is placed on a timer. During this "ignition period" the reading from the flame sensor is ignored until a large flame can be "seen" by the sensor. Once the timer has elapsed, the signal from the flame sensor is then constantly read as to monitor the burning of the combustible materials.

Inherent Motor Protection

This is provided by internal protection such as snap-disc or a thermistor.

Magnetic Overload Protection

This protection reads the actual current draw of the motor and is able to shut it off based on actual current, versus the heat-operated thermal overloads, which are sensitive to the ambient heat of a hot cabinet.