Danfoss VLT 8000 AQUA series Operating Instructions Manual

Also see for VLT 8000 AQUA series: Instruction manual Operating instructions

Contents

Danfoss VLT 8000 AQUA series Operating Instructions Manual Manual pdf 184 page image

VLT ® 8000 AQUA■ Extreme running conditionsShort circuitVLT 8000 AQUA is protected against short circuitsby means of current measurement in each of thethree motor phases. A short circuit between twooutput phases will cause an overcurrent in theinverter. However, each transistor of the inverterwill be turned off individually when the short circuitcurrent exceeds the permitted value.After 5-10 ms the driver card turns off theinverter and the frequency converter will displaya fault code, although depending on impedanceand motor frequency.Earth faultThe inverter cuts out within 100 ms in case of anearth fault on a motor phase, although dependingon impedance and motor frequency.Switching on the outputSwitching on the output between the motor and thefrequency converter is fully permitted. It is not possibleto damage VLT 8000 AQUA in any way by switching onthe output. However, fault messages may appear.Motor-generated overvoltageThe voltage in the intermediate circuit is increased whenthe motor acts as a generator. This occurs in two cases:1. The load drives the motor (at constant outputfrequency from the frequency converter), i.e.the load generates energy.2. During deceleration ("ramp-down") if the momentof inertia is high, the load is low and theramp-down time is too short for the energy to bedissipated as a loss in the frequency converter,the motor and the installation.The control unit attempts to correct the ramp ifpossible. The inverter turns off to protect thetransistors and the intermediate circuit capacitorswhen a certain voltage level is reached.Mains drop-outDuring a mains drop-out, VLT 8000 AQUA continuesuntil the intermediate circuit voltage drops below theminimum stop level, which is typically 15% below VLT8000 AQUA’s lowest rated supply voltage.The time before the inverter stops depends on the mainsvoltage before the drop-out and on the motor load.Static overloadWhen VLT 8000 AQUA is overloaded (the currentlimit in parameter 215 Current limit, I LIM has beenreached), the controls will reduce the output frequencyin an attempt to reduce the load.If the overload is excessive, a current mayoccur that makes the frequency converter cutout after approx. 1.5 sec.Operation within the current limit can be limited in time(0- 60 s) in parameter 412 Trip delay overcurrent, I LIM .MG.83.A2.02 - VLT is a registered Danfoss trademark184