Danfoss VLT 3032 Service Manual

Also see for 3000 Series: Service manual

Contents

Danfoss VLT 3032 Service Manual Manual pdf 37 page image

39When the energy returned, combined with the DC Bus voltage, exceedsthe upper voltage limit, the unit responds in different ways to limit thevoltage rise. If the returned energy is occurring during ramp down (tostop or to a lower speed), the unit will automatically adjust the decelramp in an attempt to limit the voltage. In more sever instances, theramp may even stop for periods of time to allow the voltage to dissipate.During these periods while regeneration is occurring, the words "HIGHVOLTAGE" can be observed flashing in the control card display. If thereturned energy is returned at a high enough level and/or so fast thatthe unit cannot respond, the unit will trip on "OVERVOLTAGE".To prevent a trip from occurring, one solution is to lengthen the decelramp. In applications with very high inertia loads, or in the case ofsuch loads as flywheels, the only solution may be that of adding aDynamic Brake option.The Dynamic Brake option combines a power IGBT, the electronics forcontrolling it and a resistor bank of sufficient wattage to dissipate theunwanted energy. The Dynamic Brake option monitors the level of theDC Bus voltage. When the voltage level exceeds permissible limits,the IGBT is switched on and the excess DC Bus voltage is dissipatedin the resistor bank.Particular attention must be paid to the proper sizing of the resistorbank. Consult your local representative or the factory for assistance inselecting the appropriate Dynamic Brake option for your application.Trips due to "OVERTEMP" can be due to internal or external overtemperature conditions. Two temperature sensors are located insideof the drive. One located on the Interface Board monitors the ambienttemperature within the drive itself. This normally open switch closes ata temperature of 73 to 87 degrees centigrade. The switch will reset ata temperature between 53 to 67 degrees centigrade allowing a faultreset to be possible. A fault occuring as a result of the ambienttemperature switch results in both the "IOT" and the "OTT" LED beingilluminated on the Interface Board and the Control card will display"OVERTEMP". The second sensor located on the heatsink monitorsthe surface temperature of the heatsink. This sensor is a NTC devicewhich changes in resistance value based on temperature. As thetemperature rises the resistance decreases, and conversely as thetemperature decreases the resistance increases. The sensorsresistance must be between 787 ohms and 105 K ohms to be free of afault condition. Testing this sensor is explained on page 27. A faultoccuring as a result of the NTC sensor results in the "OTT" LED on theInterface Board being illuminated and the Control Card will display"OVERTEMP". These temperature faults can be caused by high ambienttemperatures, clogged fan filters or inoperative cooling fans. Theheatsink and the door fans operate on 24VDC supplied by the InterfaceBoard."OVERVOLTAGE" TRIPS DUE TOREGENERATIVE APPLICATIONS(CONTINUED)"OVERTEMP" TRIPS