Configuration of the DC link connection

Selecting the DC link choke

DC link chokes are required for connecting inverters via the DC link. In some cases a DC link choke is not required.

• If necessary, inverters of sizes 0L – 6 are connected directly to the supply voltage ± U_Z* of the regenerative power supply via a choke.
• Inverters of sizes 7 and 8 are always connected directly to the supply voltage ± U_Z of the regenerative power supply.

The cable length refers to the distance between the inverter and the regenerative terminal on the MCR91A. The following flow diagram shows whether a DC link choke is required.

Key:

• ZD: DC link choke
• FI: Frequency inverter
• SU: Startup
• Size: Size of the device

The flow diagram must be performed individually for each inverter.

Combination of several inverters on one DC link choke for inverters

It is possible to operate several inverters on one DC link choke. The cable length is measured between the inverter under consideration and the largest device in the group. The DC link choke output or its own terminal block can be used as the DC distribution point, whereby the largest device should be connected as close as possible to the DC distribution point. If all devices are the same size, one is defined as the "largest" device. The following flow diagram shows whether a combination of several inverters is required.

Example:

Check whether 2 × MDX91A-0095.. and 1 × MDX91A-0040.. can be operated on a DC link choke.

This inverter combination can be operated on a DC link choke.

To select the suitable DC link choke, calculate the total maximum current of the inverters. The inverters mentioned have an overload capacity of 200%.

The total maximum current results from:

200% × 2 × 9.5 A + 200% × 1 × 4 A = 46 A

The sum of the maximum current of the inverters must be less than or equal to the maximum permitted total current of the DC link choke. Select the DC link choke ZD040-0070.

Maintain the maximum single cable length of 2 m between MDX91A-0095.. and the MDX91A-0095.. inverter, as well as 4 m between MDX91A-0095.. and the MDX91A-0040.. inverter. The following figure shows the schematic structure of the example:

[1]	Largest inverter
[2]	Smaller inverter
[3]	DC distribution point

The following figure shows an example of other device combinations:

[1]	Largest inverter
[2]	Smaller inverter
[3]	DC distribution point

The following figure shows an example of other device combinations:

[1]	Largest inverter
[2]	Smaller inverter
[3]	DC distribution point

• Dimensioning of the DC link connection
• Overcurrent analysis