Ac regulators
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This document discusses five types of three-phase AC power controllers: (a) line-controlled Y connection, (b) line-controlled Δ connection, (c) branch Δ connection, (d) neutral point switching using six SCRs, and (e) neutral point switching using three SCRs. The primary considerations for selecting a circuit are the output voltage level, current in the SCRs, and whether the SCRs can conduct independently. Circuits (a) and (b) produce lower voltages but higher currents, while circuits (c) and (d) allow independent SCR conduction but with higher voltages and lower currents. Circuit (e) can control output with three SCRs instead of six
Ac regulators
- 2. Three-Phase AC Phase Control There are several types of three-phase AC power controller (a) line-controlled Y connection (b) line- controlled ∆ connection (c) branch ∆ connection (d) neutral point switching using six SCRs (e) neutral point switching using three SCRs
- 4. Line- controlled ∆ connection
- 6. Neutral point switching using six SCRs
- 7. Neutral point switching using three SCRs
- 8. Three-Phase AC Phase Control The primary considerations in the selection of circuits: 1. For a given power, circuits (a) and (b) give lower voltages ( 0.866 times the supply phase voltage or half the line voltage) and higher currents in the SCR. Two SCR pairs are always required in series to block voltage or conduct current. 2. Circuit (c) gives higher voltages and lower currents in the SCRs. Each SCR can conduct current independently of the other.
- 9. Three-Phase AC Phase Control 3. Circuit (d) is functionally similar to (a). It produces identical output voltage waveforms, but since each SCR is part of only one current path instead of two, the average SCR current is halved. In addition, as in circuit (c), each SCR can conduct current independently of other. 4. For circuit (e), control of 3-phase output voltage is also possible by using 3 SCRs instead of 6. However the SCR current ratings must he doubled.