Another method is to set one external control location to speed control mode, the other
to torque control mode. Then, a digital input of the follower can be used to switch between
the control locations. See chapter Control locations and operating modes (page 23).
With torque control, follower parameter 26.15 can be used to scale the incoming torque
reference for optimal load sharing between the master and the follower. Some
torque-controlled follower applications, eg. where the torque is very low, or very low
speed operation is required, may require encoder feedback.
If a drive needs to quickly switch between master and follower statuses, one user
parameter set (see page 102) can be saved with the master settings, another with the
follower settings. The suitable settings can then be activated using for example, digital
inputs.
Load share function with a speed-controlled follower
Load sharing between the master and a speed-controlled follower can be used in various
applications. The load share function is implemented by fine-tuning the follower speed
reference with an additional trim signal based on a torque reference. The torque reference
is selected by parameter 23.42 (by default, reference 2 received from the master). Load
share is adjusted by parameter 26.15 and activated by the source selected by 23.40.
Parameter 23.41 provides a gain adjustment for the speed correction. The final correction
signal added to the speed reference is shown by 23.39. See the block diagram on page
629.
Note:
• The function can be enabled only when the drive is a speed-controlled follower in
remote control mode.
•
Drooping (25.8) is ignored when the load share function is active.
• The master and follower should have the same speed control tuning values.
•
The speed correction term is limited by the speed error window parameters 24.44
and 24.43. An active limitation is indicated by 6.19.
• For a reliable ramp stop of a follower,
•
both parameters 24.43 and 24.44 must be set smaller than parameter 21.6 (or
speed error window control disabled altogether by 24.41), and
•
parameter 24.11 must be set smaller than parameter 21.6.
Communication
A master/follower link can be built by connecting the drives together with fiber optic
cables (may require additional equipment depending on existing drive hardware), or by
wiring together the XD2D connectors of the drives. The medium is selected by parameter
60.1.
36 Program features
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