A–4

Glossary

Appendix A

Isolation

A transformer with 1:1 voltage ratio that provides electrical isolation between its primary and

Transformer

secondary windings. These are typically used on the power input side of the device to be

 

protected. An isolation transformer can protect equipment from a ground fault or other

 

malfunction of nearby equipment, as well as attenuate harmful harmonics and transients on the

 

input power.

Jogging

Operation

Jump Frequency

Usually done manually, a jog command from an operator’s panel requests the motor/drive system to run indefinitely in a particular direction, until the machine operator ends the jog operation.

A jump frequency is a point on the inverter output frequency range that you want the inverter to skip around. This feature may be used to avoid a resonant frequency, and you can program up to three jump frequencies in the inverter.

Line Reactor

A three-phase inductor generally installed in the AC input circuit of an inverter to minimize

 

harmonics and to limit short-circuit current.

Momentum

The physical property of a body in motion that causes it to continue to remain in motion. In the

 

case of motors, the rotor and attached load are rotating and possess angular momentum.

Multi-speed

The ability of a motor drive to store preset discrete speed levels for the motor, and control

Operation

motor speed according to the currently selected speed preset. The Hitachi inverters have 16

 

preset speeds.

Motor Load

In motor terminology, motor load consists of the inertia of the physical mass that is moved by

 

the motor and the related friction from guiding mechanisms. See also inertia.

NEC

The National Electric Code is a regulatory document that governs electrical power and device

 

wiring and installation in the United States.

NEMA

The National Electric Manufacturer’s Association. NEMA Codes are a published series of

 

device ratings standards. Industry uses these to evaluate or compare the performance of devices

 

made by various manufacturers to a known standard.

Open-collector OutputsOrientation

A common logic-type discrete output that uses an NPN transistor that acts as a switch to a power supply common, usually ground. The transistor’s collector is open for external connection (not connected internally). Thus, the output sinks external load current to ground.

When using the expansion card SJ-FB with encoder feedback, the orientation feature is avail- able. Also called home search in motion terminology, you can specify a search direction and a stop position. Typically the orientation procedure is necessary after each inverter powerup.

Power Factor

A ratio that expresses a phase difference (timing offset) between current and voltage supplied

 

by a power source to a load. A perfect power factor = 1.0 (no phase offset). Power factors less

 

than one cause some energy loss in power transmission wiring (source to load).

PID Loop

Proportional-Integral-Derivative – a mathematical model used for process control. A process

 

controller maintains a process variable (PV) at a setpoint (SP) by using its PID algorithm to

 

compensate for dynamic conditions and varies its output to drive the PV toward the desired

 

value. See also error.

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 (pulse-width-modulat-

 

ing), the average voltage is controlled. The chopping frequency is sometimes called the carrier

 

frequency.