Hitachi X200 Series instruction manual Pwm

A−6

Appendix A

Process Variable	A physical property of a process that is of interest because it affects
	the quality of the primary task accomplished by the process. For an
	industrial oven, temperature is the process variable. See also PID
	Loop and Error.
PWM	Pulse-width modulation: A type of AC adjustable frequency drive that
	accomplishes frequency and voltage control at the output section
	(inverter) of the drive. The drive output voltage waveform is at a
	constant amplitude, and by “chopping” the waveform (pulsewidth-
	modulating), the average voltage is controlled. The chopping
	frequency is sometimes called the Carrier Frequency.
Reactance	The impedance of inductors and capacitors has two components. The
	resistive part is constant, while the reactive part changes with
	applied frequency. These devices have a complex impedance (complex
	number), where the resistance is the real part and the reactance is
	the imaginary part.
Rectifier	An electronic device made of one or more diodes that converts AC
	power into DC power. Rectifiers are usually used in combination with
	capacitors to filter (smooth) the rectified waveform to closely
	approximate a pure DC voltage source.
Regenerative	A particular method of generating reverse torque to a motor, an
Braking	inverter will switch internally to allow the motor to become a
	generator and will either store the energy internally, deliver the
	braking energy back to the main power input, or dissipate it with a
	resistor.
Regulation	The quality of control applied to maintain a parameter of interest at a
	desired value. Usually expressed as a percent (±) from the nominal,
	motor regulation usually refers to its shaft speed.
Reverse Torque	The torque applied in the direction opposite to motor shaft rotation.
	As such, reverse torque is a decelerating force on the motor and its
	external load.
Rotor	The windings of a motor that rotate, being physically coupled to the
	motor shaft. See also Stator.
Saturation Voltage	For a transistor semiconductor device, it is in saturation when an
	increase in input current no longer results in an increase in the
	output current. The saturation voltage is the voltage drop across the
	device. The ideal saturation voltage is zero.
Sensorless Vector	A technique used in some variable-frequency drives (featured in some
Control	other Hitachi inverter model families) to rotate the force vector in the
	motor without the use of a shaft position sensor (angular). Benefits
	include an increase in torque at the lowest speed and the cost savings
	from the lack of a shaft position sensor.