Danfoss VLT AutomationDrive FC 300 User Manual

3 Introduction to the Low Harmonic Drive
3.1.1 Working Principle
The VLT Low Harmonic Drive is a VLT High Power
frequency converter with an integrated active filter. An
active filter is a device that actively monitors harmonic
distortion levels and injects compensative harmonic
current onto the line to cancel out the harmonics.
Mains
380 to
500 VAC
Optional
RFI
Optional
Fuses
Optional
Manual
Disconnect
HI Reactor
L
m
L
m
L
m
L
ac
L
ac
L
ac
AC
Contactor
Relay 12
Control & AUX
Feedback
Relay 12
Control & AUX
Feedback
Soft-Charge
Converter
Side Filter
Power Stage
AF Current
Sensors
Capacitor
Current Sensors
Frequency converter
Main’s
3
3
3
CTs
NC
Relay
L
c
L
c
L
c
C
ef
C
ef
C
ef
R
ef
R
ef
R
ef
I
r
I
s
I
t
130bb406.10
Illustration 3.1 Basic layout for the Low Harmonic Drive
3.1.2
IEEE519 Compliance
Low harmonic drives are designed to draw an ideal
sinusoidal current waveform from the supply grid with a
power factor of 1. Where traditional non linear load draws
pulse shaped currents the low harmonic drive
compensates that via the parallel filter path lowering the
stress on the supply grid. The low harmonic drive meets
the toughest harmonic standards and has a THiD of less
than 5% at full load for <3% pre-distortion on a 3%
unbalanced three-phased grid. The unit is designed to
meet IEEE519 recommendation for Isc/Il >20 for both
uneven and even individual harmonic levels. The filter
portion of the low harmonic drives has a progressive
switching frequency which leads to a wide frequency
spreads giving lower individual harmonic levels above the
50th.
0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50
0
3
4
5
6
7
8
9
10
[n]
I [%]
1
2
130BB448.10
Illustration 3.2 Typical harmonic frequency spectrum and THD
value at the mains terminals of the drive
n = harmonic order
.....IEEE519 (Isc/IL>20) limits for individual harmonics
Introduction to the Low Har... VLT Automation Low Harmonic Drive Operating Instructions
MG34O202 - VLT
®
is a registered Danfoss trademark 11
3
3

Danfoss VLT AutomationDrive FC 300 Specifications

General

Brand	Danfoss
Model	VLT AutomationDrive FC 300
Category	DC Drives
Language	English