An alternative is to reduce the load level of the motor byselecting a larger motor. However, the design of theadjustable frequency drive limits 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 additional cooling or deratingof the motor.In Figure 8.6, the typical VT curve is below the maximumtorque with derating and maximum torque with forcedcooling at all speeds.10 20 30 40 50 60 70 80 90 100 110204060801001200v %T %01)130BA893.10Figure 8.6 Maximum Load for a Standard Motor at 104°F[40°C] Driven by an Adjustable Frequency Drive─ ─ ─ ─ Typical torque at VT load─•─•─•─ Max torque with forced cooling‒‒‒‒‒ Max torqueNote 1) Oversynchronous speed operation will result in theavailable motor torque decreasing inversely proportional withthe increase in speed. This must be considered during thedesign phase to avoid overloading the motor.Table 8.16 Legend to Figure 8.68.6 TroubleshootingA warning or alarm is signaled by the relevant LED on thefront of the adjustable frequency drive and indicated by acode on the display.A warning remains active until its cause is terminated.Under certain circumstances, operation of the motor maystill continue. Warning messages are sometimes critical,but not always.In the event of an alarm, the adjustable frequency drivetrips. Reset alarms to restart operation once their cause hasbeen rectified.There are four ways to restart after an event:1. Pressing [RESET] on the LCP.2. Via a digital input with the “Reset” function.3. Via serial communication/optional serialcommunication bus.4. By resetting automatically using the Auto Resetfunction, which is a default setting for VLT® HVACDrive. See 14-20 Reset Mode in the VLT® HVACProgramming GuideNOTICE!After pressing [RESET], press the [Auto On] or [Hand On]button to restart the motor.General Specifications and ... Design Guide222 Danfoss A/S © Rev. 2014-01-13 All rights reserved. MG16C12288
