Operating instructions

Operation with only one supply frequency inverter

MICROMASTER 420 / 440 – DC link coupling between several

Frequency inverters

gland plate can be used. For the DC link fuses, the shield should be

connected to the mounting plate.

Note:

When implementing the DC link couplings, it is also important that the

plant/system and country-specific regulations are carefully observed.

4.3.3 Fusing the frequency inverter and the DC link couplings

The DC link fusing depends on the cross-section of the DC link coupling

and the max. possible fusing of the individual frequency inverters connected

at the DC link. The supply inverter is fused on the line side using fuses

recommended in the Operating Instructions of the MICROMASTER420 and

MICROMASTER440 frequency inverters; the frequency inverters which are

connected to the supply inverter must be fused at the DC link input of the

frequency inverter using the fuses specified in Tables 2-1 and 2-2. Fuses

must be provided in both the positive and negative arm of the DC link.

Note:

If the DC link coupling, originating from the supply inverter, is no longer

fused using the line-side fuses as a result of the low cable cross-section,

then this must be fused (protected) as close as possible to the supply

inverter. The fuses, specified in Tables 2-1 and 2-2 can be used for this

purpose. If the sum of the powers of the frequency inverters connected to

the DC link is less than that of the supply inverter, then this can also be

fused at the DC circuit output using fuses which have a lower rated current.

The rated current of the particular DC link fuses is then dependent on the

connected power and the cable cross-section used for the DC link

connection. The cables up to the fuses must be implemented and routed so

that they are short-circuit proof.

It is not necessary to use DC link fuses and short-circuit proof cabling, if

o the frequency inverters, connected to the DC link have the same line

fuses - as specified in the Operating Instructions - as for the supply

inverter,

and

o the cable cross-section of the DC link coupling is implemented so that

this is fused using the fuses on the line side. In this case it should be

observed that the rated DC link current IDCN, specified in Tables 2-1

and 2-2, is higher than the rated input current of the frequency inverter.

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