Toshiba G7 Series Applications Workbook page 43

Feedback Vector Control (Torque)
Introduction
Many applications may benefit from controlling torque rather than speed. Applications such as
blenders, winders, and web-tensioning devices are some of the types of equipment where torque is
the controlling factor.
One example of this type of application is an ice cream mixer. To maintain the same amount of force
on the mix by the paddle blades, the speed will decrease as the mix thickens. When the mix is thin, it
may be impossible to obtain the torque setpoint, and the speed will go to some maximum level.
Toshiba's G7, when properly configured, provides torque regulation as great as 5% (with less than
2% ripple) from 50 to 100% the motors full load torque rating.
Feedback vector torque control requires feedback from a rotary encoder mounted on the motor.
Toshiba recommends a bi-directional encoder with differential line driver outputs providing 1024
pulses per revolution.
Refer to the manual provided with the vector feedback option board for instruction on mounting and
wiring the encoder.
Torque control requires a torque command rather than a speed or frequency command. The torque
command may come from any of the G7's analog inputs, the electronic operator interface (EOI), or
one of the communication ports. In addition, torque speed limits may be configured for both forward
and reverse.
Because the G7 is primarily a speed control device, an input must be configured to switch the drive
from speed control to torque control. If the G7 will only operate in torque control mode, this control
switch may be assigned to the virtual input terminal (ON).
To maximize the performance of the motor/drive combination, the G7 must be tuned to the motor.
G7s have mathematical models of all standard efficient and premium efficient Houston-made Toshiba
motors stored in a matrix memory. These motor mathematical models are used by the drive to
increase the motor's low speed torque and to reduce the load's affect on RPM (when compared to its
performance on a V/Hz drive). If a non-Toshiba motor is being used, the G3 can model the motor by
performing an 'auto-tune' or by manual setting of the motor data.
Feedback Vector Torque Control should not be used on:
Multiple Motor Applications (applications where more than one motor is connected to the G7)
Applications where load end inductors, long lead filters, or output transformers are used
High-speed spindle motors
Motors designed for high slip (NEMA design D)
Motors larger than or more than 2 sizes smaller than the G7's nominal Horse Power rating
Before programming the G7 for feedback vector torque control, connect the motor to the drive and
check the motor's direction of rotation with a forward run command while using a constant volts per
For additional assistance, please contact Toshiba Adjustable Speed Drive Marketing Dept. at (800) 872-2192
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