Hitachi X200 Series instruction manual Squirrel Cage

		A−7
Setpoint (SP)	The setpoint is the desired value of a process variable of interest. See
	also Process Variable (PV) and PID Loop.		Appendix
Single-phase power	An AC power source consisting of Hot and Neutral wires. An Earth
	Ground connection usually accompanies them. In theory, the voltage
	potential on Neutral stays at or near Earth Ground, while Hot varies		A
	sinusoidally above and below Neutral. This power source is named
	Single Phase to differentiate it from three-phase power sources. Some
	Hitachi inverters can accept single phase input power, but they all
	output three-phase power to the motor. See also Three-phase.
Slip	The difference between the theoretical speed of a motor at no load
	(determined by its inverter output waveforms) and the actual speed.
	Some slip is essential in order to develop torque to the load, but too
	much will cause excessive heat in the motor windings and/or cause
	the motor to stall.
Squirrel Cage	A “nick-name” for the appearance of the rotor frame assembly for an
	AC induction motor.
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 that 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. Thermal switches are sometimes installed in the motor in
	order to protect the windings from heat damage. The inverter can use
	thermal switch signals to trip (shut down) if the motor overheats. See
	also Trip.
Thermistor	A type of temperature sensor that changes its resistance according to
	its temperature. The sensing range of thermistors and their
	ruggedness make them ideal for motor overheating detection. Hitachi
	inverters have built-in thermistor input circuits, which can detect an
	overheated motor and shut off (trip) the inverter output.
Three-phase power	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. Therefore, the Neutral
	connection is theoretically zero. This is why inverters that generate
	3-phase power for motors do not generally have a Neutral connection
	to the motor. However, the Earth Ground connection is important for
	safety reasons, and is provided.