Toshiba G7 Series Applications Workbook page 34

Introduction:
Many types of loads are a challenge to control with variable frequency drives. One of the more difficult loads is
the cyclic overhauling load encountered on vibratory feeders, punch presses, and pump jacks. To properly
apply variable frequency drives to loads of this nature requires a thorough understanding of the load
requirements, motor characteristics and drive capabilities.
On Cyclic Overhauling Loads, motor torque is a sinusoidal waveform which swings between positive torque
(motoring) and negative torque (regeneration). As shown in the drawings below, each cycle consists of load
and unload portion. The illustration demonstrates a cyclic overhauling cycle where the load portion causes a
load to be lifted and unloading occurs when the load is lowered. When the motor is lifting the load, the motor
is providing power. On the downstroke, the load will cause the flywheel to speed slightly faster (due to the
weight of the load) causing regeneration. When the motor is providing power to the load, torque is positive.
When the load is providing power to the motor, torque is negative.
Flywhee
Flywheel
Motor
Motor
Load
Load
0 °
charge and reach a high voltage that will trip the drive on overvoltage. Typically, dynamic braking resistors are
employed to take the regenerative energy and dissipate it as heat. With the G7 inverter, these resistors may
no longer be necessary because the drive can limit negative torque to a safe level while maintaining flux
(excitation) current at the required levels. This configuration must not be used on non-cyclic overhauling loads.
Programming
Parameter
Regeneration Torque Limit #1 (F442)
Regeneration Torque Limit #1 Setting
(F443)
Torque Limit Mode (F450)
To complete tuning, run the cyclic overhauling load while monitoring DC bus percent. A good target value is
110%. If the DC bus value is less than 110% during regeneration, increase F443. If the DC bus value is
greater than 110% during regeneration, decrease F443.
For additional assistance, please contact Toshiba Adjustable Speed Drive Marketing Dept. at (800) 872-2192
efesotomasyon.com -Toshiba inverter,drive,servo,plc
Cyclic Overhauling Loads
Flywheel
Motor
Motor
Load
90 °
180 °
Program
Torque Limit Settings
Program
Torque Limit Settings
Program
Torque Limit Settings
Flywhee
Flywhee
Motor
Load
Load
270 °
360 / 0°
How to get there
Torque Setting Parameters
Torque Setting Parameters
Manual Settings
Torque Setting Parameters
Torque Limit Mode
During the regeneration (unload)
portion of the cycle, the motor is
turning faster than the speed
that the drive is commanding it
to run. This causes power to
flow in the negative direction
from the motor to the drive. This
causes the DC bus capacitors to
New Value
'SETTING'
5%
'Positive/Negative'
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