A–2

Glossary

Appendix A

Glossary

Ambient

The air temperature in the chamber containing a powered electronic unit. A unit’s heat sinks

Temperature

rely on a lower ambient temperature in order to dissipate heat away from sensitive electronics.

Arrival Frequency The arrival frequency refers to the set output frequency of the inverter for the constant speed setting. The arrival frequency feature turns ON an output when the inverter reaches the set constant speed. The inverter has various arrival frequencies and pulsed or latched logic options.

Auto-tuning

The ability of a controller to execute a procedure that interacts with a load to determine the

 

proper coefficients to use in the control algorithm. Auto-tuning is a common feature of process

 

controllers with PID loops. Hitachi inverters feature auto-tuning to determine motor parameters

 

for optimal commutation. Auto-tuning is available as a special command from a digital

 

operator panel. See also digital operator panel.

Base Frequency

The power input frequency for which an AC induction motor is designed to operate. Most

 

motors will specify a 50 to 60 Hz value. The Hitachi inverters have a programmable base

 

frequency, so you must ensure that parameter matches the attached motor. The term base

 

frequency helps differentiate it from the carrier frequency. See also carrier frequency and

 

frequency setting.

Braking Resistor

An energy-absorbing resistor that dissipates energy from a decelerating load. Load inertia

 

causes the motor to act as a generator during deceleration. See also four-quadrant operation

 

and dynamic braking.

Break-away

The torque a motor must produce to overcome the static friction of a load in order to start the

Torque

load moving.

Carrier

The frequency of the constant, periodic, switching waveform that the inverter modulates to

Frequency

generate the AC output to the motor. See also PWM.

CE

A regulatory agency for governing the performance of electronic products in Europe. Drive

 

installations designed to have CE approval must have particular filter(s) installed in the applica-

 

tion.

Choke

An inductor that is tuned to react at radio frequencies is called a “choke,” since it attenuates

 

(chokes) frequencies above a particular threshold. Tuning is often accomplished by using a

 

movable magnetic core. In variable-frequency drive systems, a choke positioned around high-

 

current wiring can help attenuate harmful harmonics and protect equipment. See also harmon-

 

ics.

DC Braking

The inverter DC braking feature stops the AC commutation to the motor, and sends a DC

 

current through the motor windings in order to stop the motor. Also called “DC injection

 

braking,” it has little effect at high speed, and is used as the motor is nearing a stop.

DC Link

The portion of the variable frequency drive between the input rectifiers and the output stages. It

 

delivers smoothed DC power to the control and output stages of the drive.

Deadband

In a control system, the range of input change for which there is no perceptible change in the

 

output. In PID loops, the error term may have a deadband associated with it. Deadband may or

 

may not be desirable; it depends on the needs of the application.

Digital Operator

For Hitachi inverters, “digital operator panel” (DOP) refers first to the operator keypad on the

Panel

front panel of the inverter. It also includes hand-held remote keypads, which connect to the

 

inverter via a cable. Finally, the DOP Professional is a PC-based software simulation of the

 

keypad devices.