VLT ® 2000 Series I Air humidity The VLT frequency converter has been designed to meet VDE 0160, 5.2.1.2. Light dew is tolerated on internal insulating surfaces, but not during operation. Special conditions I Efficiency To reduce energy consumption it is very important to optimise the efficiency of a system. The efficiency of each single element in the system should be as high as possible. Motor efficiency ( η MOTOR ) The efficiency of a motor connected to the frequency converter depends on the sine shape of the current. In general efficiency is just as good as at mains ope- ration. The motor efficiency depends on the make of the mo- tor.
Normally the motor efficiency drops when the load is lower than the rated torque. In the range 75-100% of rated torque the efficiency of the motor will be almost constant both when operated by the frequency converter and when running directly on the mains. In general the internal switching frequency does not affect the efficiency of small motors. Efficiency of the VLT 2000 Series ( η VLT ) The load on the frequency converter has little effect on its efficiency. In general the efficiency at rated mo- tor frequency f M,N is the same whether the motor supplies a 100% rated shaft torque or only 75%. The variable switching frequency affects the losses in the VLT 2000 Series.
The efficiency will drop a little when the switching frequency is set to a value higher than 4.5 kHz. Section 1 Section 2 Section 3 System efficiency ( η SYSTEM ) To calculate the system efficiency you can multiply the efficiency of the units of the VLT 2000 Series ( η VLT ) by the efficiency of the motor ( η MOTOR ) using the below formula: η SYSTEM = η VLT x η MOTOR MG.20.B6.02 – VLT is a registered Danfoss trademark 93