SCR Phase Control Power Supplies
SCR phase control power supplies provide adjustable, regulated power to the load and reasonably fast (~few ms) shut-off in the case of a load short circuit fault. A simple discussion on phase control can be found here.
Solid State Switching Technologies:
- Typically SCRs
- 480 V, 800 A, 3 phase input power circuit breaker and contactor
- Center point, water cooled, SCR phase controller with primary (low voltage) side, 2 mH filter inductor
- Self-fired filter inductor crowbar (SCR) switch
- 45 kV, 11 A dc, oil insulated, water cooled, Transformer / Rectifier (T/R) set
- 45 kV, 54 uF filter capacitor bank
- Input voltage: 480 V, 3 phase, ac
- Output voltage: 45 kV
- Output current: 11 A
- Average power: 400 kW
- Output regulation: ~+/- 1-2%
The SCR phase controller is on left side door panel with Transformer / Rectifier (T/R) set in large grey tank in center of photo and Filter Inductor in smaller blue tank on right side. Main circuit breaker can also be seen on the enclosure panel on the right. The Filter capacitor bank is located behind the Filter Inductor oil tank.
The SCR phase controller assembly shows water cooled SCR switches, control circuitry, and power cabling to Transformer / Rectifier set and Filter Inductor.
The foreground of the photo above shows the HV power supply dump resistor bank (on right consisting of 6 series connected resistors) with HV dump relay (center) and voltage divider (left) suspended from the enclosure ceiling above the T/R set. The PFN voltage divider can also be seen in the left rear with the PFN dump circuit. Primary connections to the T/R set are seen on the lower right and the T/R set HV output bushing is in the lower left.
More details on the technical design and performance of this overall modulator system along with photos of the overall modulator may be seen on the Ness Engineering Line Type Modulator Experience page and in the published technical paper on the 520 MW Klystron Modulator System.
Photos of the solid state, command charging switch assembly and resonant charging system can be seen on the Ness Engineering
Solid State Switching Experience page and in the published technical paper on the Command Resonant Charging System for this modulator.
- Customer: Lawrence Livermore National Laboratory
- Application: Atomic Vapor Laser Isotope Separation (AVLIS) extractor (plate) power supply
- 480 V, 800 A, 3 phase, motor-operated, input power circuit breaker
- 12 pulse, water cooled, SCR phase controller (one 6 pulse in-line controller and one 6 pulse in-delta controller)
- 6 kV, 80 A dc, air insulated, transformer / rectifier set (one delta-wye T/R set and one delta-delta T/R set with rectifier bridges in series)
- 6 kV, 570 μF filter capacitor bank
- Input voltage: 480 V, 3 phase, ac
- Output voltage: 6 kV
- Output current: 80 A
- Output power: 0.5 MW
- Output regulation: Better than 1%
The photograph above shows the 480 V, 800 A, motor-operated input ac power circuit breaker along with a fused disconnect switch.
This view details the actual phase controller. Each of the six semiconductor packages on the right side of the photo are dual SCR switches. Three of each of these therefore comprise a 6 pulse SCR phase controller. Attached to the left end of each SCR package is a semiconductor fuse to protect the device in case of a short circuit fault. Power cabling is then routed through current transformers to sense the current from each SCR pair.
The SCR phase controller control electronics are shown in this photo. These electronics provide the closed loop feedback to operate the power supply and regulate the output voltage. The appropriate gate pulse signals are then generated for each of the SCRs in the phase controller to provide the requested output.
This photo shows the top portion of the air insulated Transformer / Rectifier (T/R) set. The transformer itself is located on the bottom, mostly obscured by the red panel. Diode rectifier stacks can be seen on the top of the assembly.
This is a more detailed close-up view of the T/R set rectifier stacks.
This is a side view of the 570 μF filter capacitor bank (made up of six individual 95 μF capacitors laying on their sides with output terminals facing to the right side of the photo).
On the left side is the 570 μF filter capacitor bank with bleeder resistors mounted onto the buswork on the front of the capacitors. On the right side of the photo is a large ignitron switch used as a diverter in this system to dump the stored energy in the filter capacitor bank in the case of a fault and prevent it from damaging the solid state switch array that is downstream of this hardware between it and the load.
The bottom enclosure contains the dc filter capacitor bank on the left side and ignitron diverter switch assembly located on the right side of the lower cabinet (the diverter electronics chassis indicators can be seen in the window of the bottom right). On the top of the lower enclosure are several operator control chassis for local control of the HVDC power supply and modulator.
60 kHz Modulator Overall Enclosures showing the modulator Transformer/Rectifier (T/R) Set and Phase Controller enclosure on the far right. The near enclosure on the left side contains the dc filter capacitor bank and ignitron diverter switch assembly located in the bottom half of the cabinet (the diverter electronics chassis indicators can be seen in the window of the bottom right). On top of that is the modulator portion of the system. The Series FET assembly is located in the back half of the enclosure (on the far side) while the Shunt FET assembly is lcoated in the middle bay of the top near side. To the left of the Shunt FET assembly are several operator control chassis for local control of the HVDC power supply as well as the modulator.
More details on the technical design and performance of this overall modulator system can be found in the published technical papers on the 0.5 MW 60 kHz Solid State Power Modulator and the High Power Switching Using Power FET Arrays for this modulator.