Toshiba G7 Series - Basic Drooping

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Basic Drooping
Introduction
Drooping is a torque based change in output frequency often used on applications where multiple
motors are driving a common load to ensure all motors provide torque proportional to their abilities.
On Impact loads, drooping may be used to prevent overcurrent during impact by allowing the motor to
‘slip’ on a mechanically bound system.
The G7 has eight parameters used to configure drooping. Four of the parameters interact to define
and configure drooping while four parameters are used primarily for tuning and stability. The basic
parameters used to configure drooping are:
F320 – Drooping Gain 100%
F321 – Speed at Drooping Gain 0%
F322 – Speed at Drooping Gain 100%
F323 – Drooping Insensitive Torque Band
F320 – Drooping Gain 100% -- configures the amount of droop (slip) at full motor torque based on the
scaling provided by parameters F321 and F323. Droop is applied as a linear reduction of output
frequency based on load. Ie – at 25% motor torque, the amount of frequency reduction will be 25% of
the maximum droop available at a given frequency reference based on the settings of parameters
F321 and F322.
F321-- Speed at Drooping Gain 0% -- F321 sets the frequency where the maximum amount of droop
at full load (100% motor torque) is 0%. Droop becomes ineffective at and below the frequency
specified in the parameter. Parameter F321 and F322 set the span and taper for drooping at 100%
motor torque.
F322 -- Speed at Drooping Gain 100% -- sets the frequency where the maximum amount of droop at
full load is 100% of the value specified in parameter F320. Droop above the frequency specified by
parameter F322 is based on the value programmed in parameter F320. For example, if F320 is
programmed for 10% and parameter F322 is set to 60Hz, from 60Hz and up, 100% droop is 6Hz.
As shown to the left, F320 sets the
amount of droop at 100% motor torque at
the frequency specified by parameter
F322. F321 and F322 define a linear
taper for drooping at 100% motor torque.
If parameter F320 is 10%, Parameter
F321 is 30Hz, and Parameter F322 is
60Hz, with a 60Hz command frequency
droop at 100% motor torque is 6 Hz (10% of 60). With the same configuration and a command
frequency of 45Hz, droop at 100% motor torque is 3Hz.
Command Hz
F321
F322
F320
Output Hz at 100% Torque
* For additional assistance, please contact Toshiba Adjustable Speed Drive Marketing Dept. at (800) 872-2192
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