VLT ® 2000 Series Special conditions I du/dt measurements When a transistor in the inverter is activated, the volt- age applied to the motor will rise by a flank. The du/dt ratio on the flank is determined by − Motor cable (type, cross section, length) − Inductance With short (a few metres) motor cable, the du/dt ratio will be high but the peak voltage low. With long (100 metres) motor cable, the du/dt ratio will decrease and the U PEAK peak voltage will increase. If you use very small motors without phase coil insulation we recommend to mount an LC filter in se- ries with the motor.
The self-inductance will cause an overshoot U PEAK in the motor voltage before it stabilises at a level determined by the voltage in the intermediate circuit. Both the du/dt ratio and the U PEAK peak voltage affect the lifetime of the motor. Too high values will primarily affect motors without phase coil insulation. Typical values for the du/dt ratio and the U PEAK peak voltage measured between two phases (5 m and 275 m screened motor cable) are listed below:
U PEAK [V] Cable length 5 m 275 m VLT 2030 464 V 744 V VLT 2030 with motor coil IP 20 516 V 744 V VLT 2030 with motor coil IP 00 440 V 628 V du/dt [V/ µ s] Cable length 5 m 275 m VLT 2030 3727 V/ µ s 253 V/ µ s VLT 2030 with motor coil IP 20 690 V/ µ s 157 V/ µ s VLT 2030 with motor coil IP 00 359 V/ µ s 93 V/ µ s Note: The above measurements are for VLT 2030, 1/3 x 208-240 V installed on single-phased mains I Derating for high ambient temperature The ambient temperature is the maximum temperature allowed. The average over 24 hours must be at least 5 ° C lower according to VDE 0160 5.2.1.1.
If the VLT frequency converter is operated at tempera- tures above 40 ° C, then a derating of the output current is necessary. At higher temperatures, derating will not be possible due to the load-independent temperature on the SMPS transistors. The derating for VLT 2010-2060 40 ° C: 100% output, 45 ° C: 84% output, 50 ° C: 67% output, 55 ° C: 50% output 94 MG.20.B6.02 – VLT is a registered Danfoss trademark