Technical data

RFI 1B/LC filter

The RFI 1B/LC filter contains both an RFI module that

complies with EN 55011-1B and an LC filter that re-

duces the acoustic noise.

LC filter

When a motor is controlled by a frequency converter,

at times you will be able to hear the acoustic noise from

the motor. The noise, which is caused by the design of

the motor, is generated every time one of the inverter

contacts in the frequency converter is activated. The

frequency of the acoustic noise therefore corresponds

to the frequency converter's connection frequency.

The filter reduces the voltage's du/dt, the peak voltage

peak

and ripple current I to the motor, so that the

current and voltage are almost sine-shaped. The

acoustic motor noise is thus reduced to a minimum.

Because of the ripple current in the coils some noise

will be emitted by the coils. This problem can be solved

completely by fitting the filter inside a cabinet or equiv-

alent.

Danfoss can supply an LC filter for the VLT series

2800, which muffles the acoustic motor noise . Before

the filters are put into use you must ensure that:

rated current is observed

mains voltage is 200-480 V

- parameter 412 Variable switching frequency

is set to LC filter attached [3]

output frequency is max. 120 Hz

See drawing on the next page.

Installation of thermistor (PTC)

The RFI 1B/LC filter has an integral thermistor (PTC),

which is activated if an overtemperature arises. The

frequency converter can be programmed to stop the

motor and activatee an alarm via a relay output or a

digital output if the thermistor is activated.

The thermistor must be connected between terminal

50 (+10V) and one of the digital inputs 18, 19, 27 and

29.

In parameter 128 Motor thermal protection, Thermistor

warning [1] or Thermistor trip [2] are selected

The thermistor is connected as follows:

VLT

2800 Series

14 MG.27.E3.02 - VLT

is a registered Danfoss trademark