Hitachi L200 Manual Do Utilizador

Glossary

Appendix A

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.

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 (pulse-
width-modulating), the average voltage is controlled. The chopping 
frequency is sometimes called the Carrier Frequency.

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.

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.

A particular method of generating reverse torque to a motor, an 
inverter will switch internally to allow the motor to become a gener-
ator and will either store the energy internally, deliver the braking 
energy back to the main power input, or dissipate it with a resistor.

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.

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.

The windings of a motor that rotate, being physically coupled to the 
motor shaft. See also Stator.

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.

A technique used in some variable-frequency drives (featured in 
some 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.