Vacon NX Series User Manual

Also see for NX series: User manual Applications manual Maintenance manual Operating guide Applications manual

Contents

Vacon NX Series User Manual Manual pdf 27 page image

Filter types vacon • 2524-hour support +358 (0)201 212 575 • Email: vacon@vacon.com22.3 Sine filters2.3.1 GeneralIf the motor cannot withstand any additional voltage stresses, or the dU/dt filter does not decreasethem sufficiently, a sine filter can be used. The sine filter is also LC filter, but with resonancefrequency < 50 % of the switching frequency, i.e. about 600 Hz for the 690 V drives and about 1,2 kHzfor the 500 V drives. Hence there are two different ranges. The filter removes the carrier frequency,leaving only the output frequency and thus eliminating all voltage stress on the motor.At full load the voltage drop is about 30 V - a significant part of the available voltage. This has to betaken into account when the motor sizing is done. The voltage drop can be partly compensated bydecreasing the field weakening point level; feeding the motor the correct voltage up to this point, butthe motor will not receive full voltage at nominal speed. The voltage drop can also be compensatedby using an active front end drive, increasing the DC link voltage.NOTE! The sine filters are designed for a switching frequency of 1,5 kHz for 690VAC and 3,6 kHz for500VAC, which corresponds the NX drives nominal switching frequency. It is safe to increase theswitching frequency, but IT'S NOT ALLOWED TO DECREASE THIS VALUE below nominal, as there isa risk of overheating.The Vacon NX drive has a switching frequency foldback feature on overtemperature for the drive.This has to be disabled for 500 V drives when sine filters are used. See the drive application manual.NOTE! The sine filters are designed for a maximum output frequency of 70 Hz - if this value isexceeded there is a risk of overheating. If higher output frequency is requested, the drive outputcurrent must be decreased. De-rating for motor frequency for different filter types is shown inChapter 3.4.The filters are designed in such way, that their nominal current is higher than drive's nominalcurrent. The filters are thermally designed for the same overload cycle as the drives.