Industrial Engineer · phase 8 of 16
Converter / Rectifier
Input power stage that converts incoming AC to DC, commonly with diodes, thyristors, or active semiconductor switches.
The Explain card
- Plain English
- The converter is the front end of the drive. It takes the incoming AC and turns it into DC, most often with a bridge of six diodes for a three phase supply.
- Example
- A 480 volt three phase supply goes into the rectifier and comes out as roughly 650 volts of lumpy DC on the bus. The diodes conduct in pairs as the phases take turns being highest.
- Why it matters
- A diode bridge draws current in short pulses at the peaks of the line, which is where drive harmonics come from. Losing one incoming phase leaves the bridge working on two, and the ripple and stress on the bus go up sharply.
- Hook
- The drive's first job is to forget what frequency it was fed.
Where it sits in the deck
Phase 8: VFD Drive Hardware and Power Path
Inside the drive: rectifier, DC bus and inverter, the three stages every variable frequency drive uses to rebuild the waveform a motor sees.
