Configuration 2: Parallel Connection; Example Of Drive Sizing With Permanently Connected Motors - Invertek Drives Optidrive E2 Application Note

Application note AN-ODE-2-045

Configuration 2: Parallel Connection

Output Filter
(Even required when total motor cable length is less
than maximum specified in drive manual)
With this connection method individual motor cables are run between the drive and each of the motors with a common
connection (star) point located close to the drive. Over-current protection for this configuration is typically located near to the
drive so that each motor cable down-stream from the over current protection device is rated only for the motor it protects.
The output filter is normally required for this connection method, even when the accumulative motor cable length is less than
the maximum motor cable length specified for the drive (given within the drive operating manual).

Example of Drive Sizing with permanently connected motors

An Optidrive e2 is required to control six fan motors as follows:
3 x 0.75kW, 1.9 Amps FLC
1 x 2.2kW, 5.2 Amps FLC
The Supply Voltage is 3 Phase 400 Volts. The cable length required is 10metres per fan, wired in series (configuration 1 - above).
Total Amps Required = 1.9 + 1.9 + 1.9 + 5.2 = 10.9 Amps. Referring to the Optidrive E2 User Guide, an 5.5kW 400V drive will
provide 14 Amps output current and would be suitable. The 'Motor Rated Current' parameter (P-08) should be set to 10.9 Amps.
Each motor requires an individual overload device to protect it, and an output filter is not generally required as the motors are
series connected and motor cable length is less than the maximum allowed for this drive model.
Applications where Individual Motors are Not Permanently connected to the Drive
In some applications it might be desirable to use a single drive to operate multiple motors where all of the motors are not
operating at the same time (are not always permanently connected to the drive output). Motors might be selected or
deselected by means of contactors or switches located between the individual motors and the drive output.
In such cases the best solution is to design the control system in such a way that motors cannot be connected or disconnected
whilst the drive is enabled and running. Attempting to start a motor by closing a contactor or switch on the output side of the
drive whilst the drive is enabled is likely to cause over current trips on the drive and prohibit operation.
If an application requires that different motors are run at different times (for example; in a bank of 6 fans, any number or
configuration of fans might be selected to run at any particular time) then the sequence for changing the motor fan bank
configuration would be as follows:
AN-ODE-2-045 Using Multiple Motors In Parallel
24 April 2014
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