33
3.2 Input Filters
The KEBCO line choke reduces the harmonics of the input current and the
displacement power factor of the inverter improves from 0.5... 0.6 to approxi-
mately 0.8... 0.9.
Conducted high frequency interference is reduced up to 30 db in the frequency
range from 10 kHz to approximately 300 kHz.
In addition, the noise immunity of the system is improved and the lifetime of the
DC-bus capacitors increases.
3.2.1 Line Choke
Accessories
Interference and or voltage spikes on the supply voltage are created when large
loads such as heaters, motors, arc-welders etc. are turned on and off. In some
instances, switching in and out large power factor correction capacitors either in
the factory or on the utility grid can also lead to large voltage spikes appearing
at the inverter. These spikes are typically short in time duration but high enough
in voltage to create nuisance tripping of the inverter (i.e. over voltage). The
voltage spike enters the inverter and raises the DC bus voltage level above the
predefined limit, 400V in 230V units and 800V in 460V units. The protection
circuits in the inverter activate leading to an interruption in the operation of the
unit. The choke prevents these spikes from reaching the inverter eliminating the
problem. 3% impedance chokes are generally sufficient. However 5% will help
further reduce harmonic current on the line and will allow the system to better
comply with the IEEE519 standard.
When installing larger inverters (100 hp and greater), harmonic distortion in the
line current can become a problem. This distortion is caused by the diode bridge
rectifier which serves as the input to all inverters. This distortion can create large
fluctuations in the line voltage within a facility leading to problems with other
equipment. The choke reduces the distortion of the current, there by eliminating
the associated problems.
Line Chokes - Additional Information
L1
L2
L3
GND
L1
L2
L1
L2
L3
3
2
4
1
L3
1U1
1V1
1W1
1U2
1V2
1W2
5
6
GND
GND
Connection of the line choke
1
Supply fuse
2
Disconnect switch or contactor
3
Line choke
4
Interference suppression filter
5
KEB COMBIVERT F5
6
Sub panel in control cabinet
To Next Page
Loading...
Need help?
General