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1.2 Control System
This section gives you a general overview of inverter control systems and features specific to the
FRENIC-Mini series of inverters.
As shown in Figure 1.8, single- or three-phase commercial power is converted to DC power in the
converter section, which is then used to charge the capacitor on the DC link bus. According to control
commands or signals generated in the control logic, the inverter modulates the electricity charged in
the capacitor to PWM (Pulse Width Modulation) format and feeds the output to the motor. The
modulation frequency is called "carrier frequency." As shown in Figure 1.7, the voltage waveform of
the modulated power source produces pulse train with positive and negative polarity synchronized
with the inverter's output command frequency. The inverter feeds the produced output as drive power
with sinusoidal current waveform like that of ordinary commercial power lines.
PWM voltage waveform Current waveform
Figure 1.7 Output Voltage and Current Waveform of the Inverter
For the reference frequency given in the control logic, the accelerator/decelerator processor calculates
the acceleration/deceleration rate required by run/stop control of the motor and transfers the calculated
results to the 3-phase voltage command processor directly or via the V/f pattern generator.
Refer to Chapter 4, Section 4.7 "Drive Command Controller" for details.
The FRENIC-Mini series changes the voltage control from the "Simplified Torque-Vector Control"
using a magnetic flux estimator in conventional inverter series, to the Dynamic Torque Vector Control
adopted in upper inverter series. Accordingly, the FRENIC-Mini series assures high start torque that
the conventional series cannot obtain, broadening the range of applications.
The control logic section, which is the very brain of the inverter, allows you to customize the inverter's
driving patterns using the function code settings.
Refer to Chapter 4 "BLOCK DIAGRAMS FOR CONTROL LOGIC" for details.
Figure 1.8 Simplified Control System Diagram of FRENIC-Mini
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