VLT ® 2000 Series Special conditions I Acoustic noise The acoustic noise from the frequency converter is generated from 3 sources: 1. The motor coils (if mounted) generate a 4.5 kHz noise, which is dependent on the cable impedance. 2. The DC coils (if mounted) generate a 100 Hz noise (300 Hz, three-phase), which is proportional with the motor load. 3. The noise from the built-in fan (not integrated in all units) is acceptable to the human ear, although the measurements show the highest values for fan noise. The values below (sound pressure) have been meas- ured in accordance with VDE 0160.4.2 standard at a distance of 1 metre from the VLT frequency converter at 100% load and rated speed.
VLT type 2010 2015 2020 *) 2030 *) 2040*) 2050*) 2020 2025 2030 2040 *) 2050 *) 2060 *) IP 20 dB (A) 30.1 30.1 50.7 50.7 50.7 50.7 30.1 30.1 30.1 50.7 50.7 50.7 *) with built-in fan. I Motor noise The motor noise depends mainly on the motor, but as a guideline the noise increases by about 10 dB (A) in relation to direct mains operation. If a higher switching frequency is chosen the noise from the motor will decrease. How much will depend on the motor resonance and the type of motor. I Extreme running conditions The control unit attempts to correct the ramp if possible. The inverter turns off to protect the transistors and the intermediate capactors, when a certain voltage level is reached.
Short circuit VLT 2000 Series is protected against short circuits. A short circuit between two output phases will cause overcurrent in the inverter. However, each switch of the inverter will be turned off individually when the short circuit current exceeds the permitted value. Mains drop-out During a mains drop-out the VLT frequency converter will continue to operate until the intermediate circuit voltage drops below the minimum stop level, typically 85% of the VLT frequency converter’s rated mains supply voltage. The time before inverter stop depends on mains volt- age before drop-out and the motor load. Ride-through can be programmed.
Ground fault In case of an ground fault in a motor phase, the inverter is turned off within 5-10 ms. Switching on the output (only using motor chokes) Switching on the output between the motor and the frequency converter is fully permitted. It is not possible to damage the VLT frequency converter in any way by switching on the output, although it may result in some occasional tripping conditions. Static overload When the VLT frequency converter is overloaded (the current limit I LIM i is reached) the control unit will reduce the output frequency f M in an attempt to reduce the load.
If the reduction of the output frequency does not reduce the load, the control unit finally trips when the output frequency has dropped below 1 Hz. Motor-generated overvoltage The voltage on the intermediate circuit will be increased when the motor acts as a generator. This takes place in two cases: 1. The load runs the motor (at constant output frequency from the frequency converer), i.e. energy is supplied from the load. 2. During deceleration ("ramp-down"), if the moment of inertia is high, the load is low and/or the ramp-down time is short. Running at current limit is limited (0-60 sec). 92 MG.20.B6.02 – VLT is a registered Danfoss trademark