Danfoss VLT AQUA Drive FC 202 Design Manual

Also see for VLT AQUA Drive FC 202: Service guide Installation guide Installation guide Operating guide Installation guide

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An alternative is to lower the ambient temperature at highaltitudes and ensure 100% output current at high altitudes.As an example of how to read the graph, the situation at 2km is elaborated. At a temperature of 45 °C (TAMB, MAX - 3.3K), 91% of the rated output current is available. At atemperature of 41.7 °C, 100% of the rated output currentis available.800 5001009590851000 1500 2000 2500 3000Altitude (meters above sea level)*130BB008.10IOUT (%)Illustration 3.3 Derating of Output Current Versus Altitude atTAMB, MAX0 500 1000 1500 2000 2500 3000Altitude (meters above sea level)*30354045(°C)Amb. Temp.130BB009.10HONOIllustration 3.4 Derating of Output Current Versus Altitude atTAMB, MAX3.5.3 Derating for Running at Low SpeedWhen a motor is connected to a frequency converter, it isnecessary to check that the cooling of the motor isadequate.The level of heating depends on the load on the motor, aswell as the operating speed and time.Constant torque applications (CT mode)In constant torque applications, it is possible for a motorto draw full current while operating at slow speeds. Insuch cases, the cooling fins do not adequately cool themotor, causing it to overheat. When the motor is operatingcontinuously at less than half its rated speed, apply morecooling.Alternately, an oversized motor can be used to reduce theload level. However, the size of the motor is limited to onesize larger than that specified by the frequency converter.An alternative is to reduce the load level of the motor bychoosing a larger motor. However, the design of thefrequency converter puts a limit to the motor size.Variable (Quadratic) torque applications (VT)In VT applications such as centrifugal pumps and fans,where the torque is proportional to the square of thespeed and the power is proportional to the cube of thespeed, there is no need for more cooling or de-rating ofthe motor.In the graphs shown below, the typical VT curve is belowthe maximum torque with de-rating and maximum torquewith forced cooling at all speeds.10 20 30 40 50 60 70 80 90 100 110204060801001200v %T %01)130BA893.10Illustration 3.5 Maximum Load for a Standard Motor at 40 °C─ ─ ─ ─ Typical torque at VT load─•─•─•─ Max torque with forced cooling‒‒‒‒‒ Max torqueTable 3.15 Legend to Illustration 3.5NOTEOver-synchronous speed operation results in the availablemotor torque decreasing inversely proportional with theincrease in speed. Consider this decrease during the designphase to avoid overloading the motor.Selection VLT® AQUA Drive FC 202 Design GuideMG20Z102 - VLT® is a registered Danfoss trademark 533 3