Hitachi L100 Windings in a motor that are stationary and coupled to, Windings from heat damage

L100 Inverter

A–7

Stator	The windings in a motor that are stationary and coupled to the
	power input of the motor. See also rotor.
Tachometer	1. A signal generator usually attached to the motor shaft for the
	purpose of providing feedback to the speed controlling device of
	the motor. 2. A speed-monitoring test meter which may optically
	sense shaft rotation speed and display it on a readout.
Thermal Switch	An electromechanical safety device that opens to stop current flow
	when the temperature at the device reaches a specific temperature
	threshold. In variable-speed drive systems, thermal switches are
	typically installed at or near the motor, in order to protect the
	windings from heat damage.

Appendix A

Three-phase	An AC power source with three Hot connections that have phase
	offsets of 120 degrees is a 3-phase power source. Usually, Neutral
	and Earth Ground wires accompany the three Hot connections.
	Loads may be configured in a delta or Y configuration. A Y-
	connected load such as an AC induction motor will be a balanced
	load; the currents in all the Hot connections are the same. There-
	fore, the Neutral connection is theoretically zero. This is why
	inverters, which generate 3-phase power for motors, do not gener-
	ally have a Neutral connection to the motor. However, the Earth
	Ground connection is important for safety reasons, and is provided.
Torque	The rotational force exerted by a motor shaft. The units of measure-
	ment consist of the distance (radius from shaft center axis) and
	force (weight) applied at that distance. Units are usually given as
	pound-feet, ounce-inches, or Newton-meters.
Transistor	A solid state, three-terminal device that provides amplification of
	signals and can be used for switching and control. While transistors
	have a linear operating range, inverters use them as high-powered
	switches. Recent developments in power semiconductors has
	produced transistors capable of handling hundreds of volts and tens
	of Amperes or more, all with high reliability. The saturation voltage
	has been decreasing, resulting in less heat dissipation. Hitachi
	inverters use state-of-the-art semiconductors to provide high perfor-
	mance and reliability, all in a compact package. See also IGBT and
	saturation voltage.
Trip	An event which causes the inverter to stop operation is called a
	“trip” event (as in tripping a circuit breaker). The inverter keeps a
	history log of trip events. They also require an action to clear.