Operating instructions

Operation with only one supply frequency inverter

MICROMASTER 420 / 440 – DC link coupling between several

Frequency inverters

The DC braking – function in the inverter can be used as an alternative to

regenerative braking using the integrated braking chopper. This can be

activated for every connected frequency inverter. It is not permissible that

the compound braking is activated. The reason for this is that this can

automatically be switched-in, as a function of the DC link voltage and result

in undesirable braking operations.

4.5 Max. motor cable lengths

The max. motor cable length of all of the frequency inverters connected in

the DC link group may not exceed, in total, 200m (shielded) and 300m

(non-shielded). Otherwise, their rectifier and the EMC filters could be

overloaded due to the discharge (leakage currents) which flow with respect

to PE and which flow back through the supply inverter. An output reactor

should be used for the individual frequency inverters for motor cable lengths

exceeding 50m (shielded) and 100m (non-shielded) as specified in Catalog

DA51.2.

4.6 DC link voltage controller operation

For a DC link coupling, the V

DCmax

controller, integrated in the

MICROMASTER 420 and MICROMASTER 440 frequency inverters may

not be used. This controller is activated in the factory setting which means

that it must be disabled by setting parameter P1240 to 0.

However, the kinetic buffering in the MICROMASTER 440 frequency

inverter can be used to buffer the DC link during brief power failures. In this

case, parameter P1240 must be set to 2.

4.7 Accommodating the frequency inverters connected to the DC

link in a cabinet

The frequency inverters, coupled through the DC link, must be located next

to one another in the electric cabinet in the same sequence as their rated

powers. Generally, the supply inverter is the inverter with the highest power

rating in the DC link group. The frequency inverters must be arranged

directly next to one another in order to keep the DC link couplings as short

as possible.

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