VLT ® 2000 Series I Derating for air pressure Below 1,000 metres altitude no derating is necessary. Above 1,000 metres the T amb or maximum output power must be derated according to the figure below. Special conditions Derating for air pressure 1. Derating of output current versus altitude at T amb 40 ° C. 2. Derating of max. T amb versus altitude at 100% output current. Section 1 Section 2 Section 3 I Derating for running at low speed No derating is necessary when running the motor at rated speed, or when controlling a fan or centrifugal pump. Motors running at constant load torque (CT) used at low speed must be derated or fan-cooled (see dia- gram).
Typical motor derating I Derating for higher switching frequency than 4.5 kHz A higher switching frequency means higher losses and increased heat generation in the transistors and motor coils of the frequency converter. Therefore the VLT frequency converter automatically reduces the maximum continous output current I VLT,N when the switching frequency exceeds 4.5 kHz. The reduction is done linearly to 60% at 16 kHz (see dia- gram). The maximum permitted motor cable length is 40 m of screened cable. Derating for higher switching frequency 100% I VLT ➤ 60% 20% 2 4.5 16 f sw [kHz] ➤ MG.20.B6.02 – VLT is a registered Danfoss trademark 95