Specifications

102
Terminology
（1）Vector Controls
Current vector: Directly controls the flux current and torque
current that generates motor flux and torque.
The primary current size I 1 and phase
φand controlled simultaneously.
Flux current Im = I 1 cosφ
Torque current I
2 = I 1 sinφ
(Motor torque = kIm・I
2)
Since this control directly affects the
final target torque, response is fast
and precision is high.
Voltage vector: Indirectly controls the motor flux and torque
via the voltage.
This control can be equivalent to the
current vector if the primary circuit of
the motor is known completely, but
this is actually difficult since the
temperature of the resistance also
changes.
（2）Auto-tuning
Auto-tuning in the Varispeed G7, allows automatic
measurement of motor constant necessary for vector control.
As a result, this function changes the vector control drive not
only for YASKAWA motors but for any other existing motor
into an outstanding performance drive.
（3）Automatic Torque Boost
Torque boost is to compensate for the drop by primary
resistance to the V/f constant voltage to supplement the
decrease of the flux due to voltage drop within the motor at
V/f constant control.
The V/f mode of the Varispeed G7 incorporates automatic
torque boost for automatic compensation according to the
load, accommodating the vector control principle.
（4）Regenerative Braking
The motor is operated as a generator, converting mechanical
energy into electric energy, to generate braking force while
feeding back energy to the inverter or power supply.
The energy is fed back to the smoothing capacitor within the
inverter under regeneration status (the motor is under
regenerative braking status), where it its absorbed or
consumed as motor loss.
（5）12-pulse Input Control
It is a circuit method to provide a 30-degree deflected phase
power supply to two converters by star delta wiring of the
transformer. Fifth and seventh components of high
harmonics of power supply side current can be significantly
reduced.
12-pulse input control using a transformer with a dual star
delta secondary will reduce the effects on peripheral devices
caused by a high harmonic power supply.
（6）High Harmonics
Harmonic input distortion can be minimized by attaching AC
reactor to the input side or DC reactor in the main circuit.
The Varispeed G7 models of 18.5 kW or more come equipped
with a built-in DC reactor. When 12-pulse input option is
utilized, current distortion is much more improved.
（7）Leakage Current
Current leak always occurs when voltage is applied to any
component, even if it is insulated. The PWM inverter includes
high frequency components in the output voltage, especially
increasing the leak current that flows through the floating
capacity of the circuit. However, leakage current of high
frequency (of some kHz) presents no hazard to personnel.
（8）Noise
Noise may be generated when the inverter operates, affecting
peripheral electronic devices. The transmission mediums of
this noise are air (as electric wave), induction from the main
circuit wiring, power source lines, etc.
The noise that is transmitted through the air, affecting
surrounding electronic devices is called radio noise.
The noise can mostly be prevented by enclosing each
inverter in a metallic cabinet, ensuring adequate grounding,
or separating electronic circuits from the magnetic cabinet.
However, a noise filter may sometimes be required to reduce
noise interference to an acceptable level.
I2 I1
Im
φ
Voltage
Motor
Primary
Circuit
Motor
Flux Current
Torque Current
Current Vector
Voltage Vector
Flux
Torque