WEG MVW3000 A0040 V023, User Manual

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MVW3000 | 8-1
8
Special Functions
MVW3000 | 8-1
8 SPECIAL FUNCTIONS
8.1 LOAD SHARE FUNCTION “MASTER/SLAVE”
Conveyors belts and overhead cranes are classic examples of applications where the torque or position control
is used to maintain the conveyor belt voltage within the limits during the operation, start and stop procedures or
even in the transportation of materials in a rising of falling slope.
For motors connected to the same load, it is necessary to ensure a reliable load sharing. Such characteristic is
best achieved with the use of multiple inverters operating in speed reference mode (Master) and torque limitation
mode (Slave (s)).
Implementation Modes
Three modes to implement the load sharing function will be presented. For the first two modes, it is mandatory
that the inverters involved in the process be set to vector operating mode. For most applications, the vector
operating mode with speed or position sensor is recommended.
In order to implement the load sharing, the inverter assigned as master controls the load speed using all the other
inverters of the process as actuators.
In the vector mode, there are two ways to implement the load sharing function: in the first one, the master inverter
sends the slaves the torque reference signal; in the second one, it sends the torque reference limitation signal.
The mode to be used must be analyzed for each application.
For operation in scalar mode with load sharing, all inverters must receive the same speed reference signal. This
type of load sharing is called “droop” or negative slip.
The three implementation methods and the main parameters used in each method are shown below.
Torque Reference - Operation in Vector Mode
One of the possible ways to implement the load sharing function is by parameterizing the salve inverter(s) to follow
an external torque reference, which will be sent by the master inverter.
...
...
MVW3000
Master
Speed ref.
Torque ref.
MVC4
MVC3
AOX
MVC3
AIX
MVC3
AIX
MVW3000
Slave 1
MVW3000
Slave n
Figure 8.1: General operation scheme of the function
In order to do so, the inverters must be parameterized as follows:
Master:
Parameterize one of the analog outputs of the MVC3 control board to send the torque reference to the slave
inverter(s). In the example below, the analog output AO1 is parameterized.
P0652 (Analog Output 1 Function) = 188 (Inverter torque reference).