Drooping - Toshiba G3 Workbook

Introduction
Also called load share, drooping control can be used to share load among two or more
mechanically- coupled motors. Unlike stall, which reduces output frequency in order to limit load once
load reaches a set level, droop is a linear load-based reduction in output frequency effective at all torque
currents (up to 200% load).
Due to variances in gearboxes, sheaves, belts, and in the motors themselves, and since the speed of
the motors is constrained by the mechanical system, one motor may experience more load than its
counterpart and may become overloaded. Drooping allows the overloaded motor to slow down,
thus shedding load and encouraging a lightly-loaded motor to pick up the slack. The goal of drooping
control is to have the same torque ratios (actual torque/rated torque) for both motors.
Example System
G3
#1
Programming
UTILITY PARAMETERS
UTILITY PARAMETERS
FEEDBACK PARAMETERS
FEEDBACK PARAMETERS
Drooping Control Enable can be turned on/off while drive is running, but change will not take
effect until drive is stopped. Drooping Control Amount can be changed on the fly, however.
Equations
Output frequency = drive's internal frequency reference (after ACC/DEC) - Droop Frequency
Droop Frequency = MAXIMUM OUTPUT FREQUENCY x DROOPING CONTROL AMOUNT x
Torque Ratio
Torque Ratio (max 200%) = instantaneous actual torque / rated torque
* adjusted on site. See page 2 for procedure.
For additional assistance, please contact Toshiba Adjustable Speed Drive Marketing Dept. at (800) 872-

Drooping

CONVEYOR
Motor 1
Common frequency reference
Group
Motor 2
G3
#2
Parameter
Blind Function Selection
Feedback Parameters Blind
Drooping Control Enable
Drooping Control Amount
2192
28
New Value
1
1
1
*
70