A–2

Glossary

Appendix A

Glossary

Ambient Temperature

The air temperature in the chamber containing a powered electronic

 

unit. A unit’s heat sinks 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 avail-

 

able 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 deceler-

 

ating load. Load inertia causes the motor to act as a generator

 

during deceleration. See also Four-quadrant Operation and

 

Dynamic Braking.

Break-away Torque

The torque a motor must produce to overcome the static friction of a

 

load, in order to start the load moving.

Carrier Frequency

The frequency of the constant, periodic, switching waveform that

 

the inverter modulates to 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 application.

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 Harmonics.