Section 3, Principles of operation/applications, Principles op 0perati0n/appucati0ns – Toshiba VT130G1 User Manual
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Section 3
PRINCIPLES OF OPERATION/APPLICATIONS
Most A.C. induction motors in the past have been limited to fixed speeds. The Toshiba
motor drive provides a simulated (RW.M.) A.C. that varies the speed of the motor.
Toshiba’s giant transistor (G-TR) is used with a microprocessor corttrolled regulator to
accomplish the conversion.
Motor speed ratings usually show the motor base speed at 60 HZ operation. Slower
speeds (below base speed) are produced by reducing both the voltage and the fre>
quency of the output.
H MOTOR
VOLTAQE
Figure 3-1 shows the voltage vary
ing with the frequency until base
speed (60 HZ) is reached. Above
base speed, the voltage remains
constant.
P.W.M. (Pulse Width Modulated) inverters change the incoming power to D.C. and then
pulse the D.C. into the motor leads to simulate A.C. Figu'e 3-2 shows a representation of
the Toshiba output voltage waveform.
An A.C. waveform is super
imposed on the pulse wave
for illustration.
Ni
FIGURE 3-2