Danfoss VLT 2800 Design Manual

Also see for VLT 2800: Operating instructions Manual Instruction manual Quick guide Installation instructions

Contents

Danfoss VLT 2800 Design Manual Manual pdf 15 page image

1.7.11 RFI 1B/LC FilterThe RFI 1B/LC filter contains both an RFI module thatcomplies with EN 55011-1B, and a LC filter that reducesthe acoustic noise.LC filterIllustration 1.4 LC FilterWhen a motor is controlled by a frequency converter,acoustic noise may be heard from the motor. The noise,which is caused by the design of the motor, is generatedevery time one of the inverter contacts in the frequencyconverter is activated. The frequency of the acoustic noisetherefore corresponds to the frequency converter'sconnection frequency.The filter reduces the voltage's dU/dt, the peak voltageUpeak and ripple current ΔI to the motor, so that thecurrent and voltage are almost sine-shaped. The acousticmotor noise is thus reduced to a minimum.Because of the ripple current in the coils, some noise isemitted by the coils. This problem can be solvedcompletely by fitting the filter inside a cabinet orequivalent.Danfoss can supply an LC filter for the VLT series 2800,which muffles the acoustic motor noise. Before the filtersare put into use, ensure that:• Rated current is observed.• Mains voltage is 200-480 V.• Parameter 412 Variable switching frequency is setto [3] LC filter attached.• Output frequency is max. 120 Hz.Refer to Illustration 1.7 for a connection example of LCfilter.Installation of thermistor (PTC)The RFI 1B/LC filter has an integral thermistor (PTC), whichis activated if an overtemperature arises. The frequencyconverter can be programmed to stop the motor andactivate an alarm via a relay output or a digital output ifthe thermistor is activated.Illustration 1.5 Thermistor InstallationThe thermistor must be connected between terminal 50(+10 V) and one of the digital inputs 18, 19, 27 and 29.In parameter 128 Thermal motor protection, [1] Thermistorwarning or [2] Thermistor trip is selected.Illustration 1.7 shows the thermistor connection.Illustration 1.6 Thermistor ConnectionTo comply with EN 55011-1B, the RFI 1B filter module mustbe fitted to a VLT 2800 with integral 1A RFI filter.NOTICEThe 1B/LC filter is not suitable for 200 V devices due tothe high 1Ø input current.Introduction to VLT 2800 Design GuideMG27E402 Danfoss A/S © Rev. May/2014 All rights reserved. 131 1