A–5

SJ300 Inverter

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 imped-

 

ance (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.

A Appendix

Regenerative BrakingRegulationReverse TorqueRotorSaturation

Voltage

Sensorless Vector ControlSetpoint (SP)Single-phase Power

A particular method of generating reverse torque to a motor, an 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.

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 variable-frequency drives 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.

The setpoint is the desired value of a process variable of interest. See also Process Variable (PV) and PID Loop.

An AC power source consisting of Hot and Neutral wires. An Earth Ground connection usually accompanies them. In theory, the voltage potential on Neutral stays at or near Earth Ground, while Hot varies sinusoidally above and below Neutral. This power source is named Single Phase to differentiate it from three-phase power sources. Some Hitachi inverters can accept single phase input power, but they all output three-phase power to the motor. See also three- phase.

Slip

The difference between the theoretical (synchronous) speed of a motor at no load (determined

 

by its inverter output waveforms) and the actual speed. Some slip is essential in order to

 

develop torque to the load, but too much will cause excessive heat in the motor windings and/or

 

cause the motor to stall.

Squirrel Cage

A “nick-name” for the appearance of the rotor frame assembly for an AC induction motor.

Stator

The windings in a motor that are stationary and coupled to the power input of the motor. See

 

also rotor.

Start Frequency

The output frequency that the inverter first produces as the frequency command setting

 

increases from zero. The start frequency is programmable, and is important to set properly for

 

the load, etc.

Tachometer

1. A signal generator usually attached to the motor shaft for the purpose of providing feedback

 

to the speed controlling device of the motor. 2. A speed-monitoring test meter that may

 

optically sense shaft rotation speed and display it on a readout.