Power Electronic Converters

Frequency converter operation

Frequency converter
 
In this section we will focus on the power handling section of the frequency converter. A standard frequency converter is shown to the right, the power-handling sub- circuits are:
• Input filter
• Rectifier
• Energy storage circuit or Intermediate circuit
• Inverter

The function of the different components in the sub circuit is:
Input filter
The input filter prevents that noise generated inside
the frequency converter reaches other components
connected to the mains. It also prevents that noise
from the mains reaches and disturbs the frequency
converter.
Rectifier
The rectifier rectifies the mains voltage into a pulsating
DC voltage.
Energy storage circuit or intermediate circuit
The pulsating DC voltage from the rectifier is sent to the energy storage circuit, where it is transformed into a DC voltage with an additional AC ripple. The magnitude of the AC ripple depends on the load on the inverter. No load means no ripple.
Inverter
The inverter converts the DC voltage into an output voltage of variable frequency and amplitude. The inverter has six switches that can either be switched on or off. In the next section we will concentrate on the performance of the inverter.



The function of the inverter
The six switches in the inverter are switched in a pattern so that a circulating field is created in the stator. The switch pattern reflects the actual output voltage and frequency of the frequency converter.

Single Phase to Three Phase Convertor

Arno Convertor

This is a rotary convertor which has a combined set of windings and is used to convert the single phase supply from the Tertiary winding of the Loco transformer to Three-Phase AC which is fit for use by the various Auxiliary machines in the loco.