Input Rectifier; Sizing; Line Reactance - WEG CFW11W G2 Series User Manual

3.2.1 Input Rectifier

It is necessary to use a rectifier to generate DC voltage for the power supply of the UP11W G2. The rectifier may
be an Active Front End (AFE), diode rectifier of 6, 12, 18 pulses or more.
The following items contain general directions on the sizing of a 6-pulse rectifier. For further information on multipulse
rectifiers or AFE, contact WEG.

3.2.1.1 Sizing

The main rectifier bridge is sized according to the drive rated power. The heat dissipation caused by the losses
on the rectifier bridge must be taken into account both in the sizing of the bridge heatsink and in the heating of
the air inside the panel.
ATTENTION!
It is recommended that the diodes of the bridge have a reverse voltage ≥ 2200 V.

3.2.1.2 Line Reactance

The diode rectifier plus the capacitor bank of the UP11W G2 drain from the power grid a current with non-
sinusoidal wave shape containing harmonics of the fundamental frequency. Those harmonic currents flowing on
the impedances of the power line cause harmonic voltage drops, distorting the supply voltage of the inverter itself
or of other consumers. As an effect of those current and voltage harmonic distortions, we may have an increase
in the electrical losses on the installations with the overheating of its components (cables, transformers, capacitor
banks, motors, etc.), as well as a low power factor.
The input current harmonics depend on the values of the impedances present on the rectifier input/output circuit.
The addition of a line reactance reduces the current harmonic content, providing the following advantages:
Increase of the power factor on the inverter input.
„
Reduction of the effective input current.
„
Reduction of the voltage distortion on the supply line.
„
Increase of the useful life of the DC link capacitors.
„
For the calculation of the line reactance necessary to obtain the desired percentage voltage drop, use:
ATTENTION!
It is recommended a line reactance of at least 3 % on the input of the 6-pulse diode rectifier.
Voltage drop [%] . Line voltage [V]
L =
line
3.2 . π . Line Freq [Hz] . I
Installation and Connection
. [A].100
Rated Cur
3
CFW-11W G2 | 3-13