Installation manual

Droop Control
146 S1A53838 09/2011
Droop control principle
The use of droop control (or negative slip compensation) can help balance the load between multiple motors in
a load sharing application. The amount of slip or speed droop allowed in the motor powering the load is
determined by the load current level and the setting of parameters F320 and F323.
During motoring, droop control decreases the drive output frequency. During regenerative braking, droop control
increases the drive output frequency.
When enabled, droop control is active when:
z The load current exceeds the level set by parameter F323.
z The drive output frequency is between the [Mot start freq.] F240 (see page 82) and [Max frequency] (FH)
(see page 82).
The amount of speed droop allowed (f) can be calculated by this equation:
f = uL(1) x F320 x (load current – F323)(2)
Example:
uL = 60 Hz
F320 = 10%
F323 = 30% (of drive’s rated current)
Load current = 100% of drive’s rating
f = 60 x 0.1 x (1 – 0.3)
f = 60 x 0.07
f = 4.2
Assuming the speed reference is set to 60 Hz, the output frequency will be: f1 = f0 – f = 60 – 4.2 = 55.8 (Hz).
(1) Parameter [Motor Rated freq] (uL) (see page 70). The value entered for uL in this formula should not exceed 100,
regardless of the actual setting of parameter uL.
(2) Speed droop is zero if (load current – F323 = 0).
(3) Percent of the drive’s rated current.
0 100%T1
Output frequency (Hz)
Command frequency: f
0
Power running
Torque current (%)
Operation frequency: f
1
Code Name / Description Adjustment range Factory setting
F320 [Load gain]
0 to 100% 0%
F323 [Load gain offset]
0 to 100% (3) 10%