12
SPECIAL FUNCTIONS
12.1.4 Negative Slip – Operation in Scalar Mode
This method to implement the load sharing function is limited to applications of induction motor drive. It is based on the decrease of the
frequency according to the increase of load on the motor; thus there is a natural distribution of the loads.
Regardless of the chosen speed reference source, it must be sent to all inverters. Due to the low accuracy of analog inputs, its use as speed
reference source is not recommended.
This method to implement the load sharing must not be used for applications that require dynamic performance, and it can only be considered
when the inverters drive motors with the same characteristic slip.
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Mestre Escravo 1 Escravo n
MVC3
AOx
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MVC3
AIx
MVC3
AIx
MVC4
AOx
MVC4
AIx
MVC4
AIx
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Mestre Escravo 1 Escravo n
MVC3
AOx
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MVC3
AIx
MVC3
AIx
MVC4
AOx
MVC4
AIx
MVC4
AIx
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PLC, Networks, ...
Speed ref.
PLC, Networks, ... PLC, Networks, ...
MVW01 MVW01
Auxiliary 1
MVW01
Auxiliary nMain
Figure 12.3: General operation scheme of the function
Therefore, the inverters must be parameterized as follows:
P0138 (Rated slip) = the motor slip is recommended (negative signal).
P0139 (Output current filter) = it is recommended to start with the standard value and gradually increment it if the system presents instability.
Besides the presented parameterization, the implementation of the load sharing function requires that all inverters involved in the process be
enabled simultaneously; thus, the “General Enable” and “Run/Stop” signals must be sent to all inverters at the same time. There are several
ways to meet this requirement and the most appropriate way will depend on each application.
The description given of the ways to implement the load sharing function intends neither to approach all possibilities of implementation, nor to
detail all the aspects involved. The definition of the best implementation mode for a certain application, as well as the optimal adjustment of
each mode must be defined by WEG engineering and application teams.
MVW01 | 12-3
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