Can a stack of Tyristors be a switch?

[Breakable]

Just wondering if Tyristors were considered for a switch application. Are they not fast enough?

Since modern thyristors can switch power on the scale of megawatts, thyristor valves have become the heart of high-voltage direct current (HVDC) conversion either to or from alternating current. In the realm of this and other very high power applications, both electrically triggered (ETT) and light triggered (LTT) thyristors[3] are still the primary choice. The valves are arranged in stacks usually suspended from the ceiling of a transmission building called a valve hall. Thyristors are arranged into a diode bridge circuit and to reduce harmonics are connected in series to form a 12 pulse converter. Each thyristor is cooled with deionized water, and the entire arrangement becomes one of multiple identical modules forming a layer in a multilayer valve stack called a quadruple valve. Three such stacks are typically mounted on the floor or hung from the ceiling of the valve hall of a long distance transmission facility.[4][5]

Manitoba Hydro Electric power station uses Thyristor stacks to
transmit multi megawatt loads, and the SCR/TRIAC/QUADRAC
are derived switches, do not know if they are fast enough thou

[Breakable]

Thyristors (also known as the Silicon Controlled Rectifiers or SCRs) have come a long way from this modest beginning and now high power light triggered thyristors with blocking voltage in excess of 6kv and continuous current rating in excess of 4kA are available.

http://www.nptel.iitm.ac.in/courses/Webcourse-contents/IIT Kharagpur/Power Electronics/PDF/L-4(DK)(PE) ((EE)NPTEL).pdf

They are also widely used as fast acting protection devices in DC power supplies. The switching speed of thyristors is very fast and they are able to switch from fully off to fully on, typically in 1µs.

http://www.learnabout-electronics.org/diodes_06.php

Price is probably the main concern?

[asymmetric_implosion]

The main concerns are slew rate (rate of change of the current), voltage hold off and price.

Slew rate: SCR’s are very limited in slew rate for a PF. The common solution is to use saturatable magnet cores that choke the current until they saturate. The cores need to be reset after every shot but that is known technology.

Voltage hold off: SCR switches are limited to a few kV so a stack is required. Firing multiple switches in series is challenging but not impossible. The problem is the voltage from the pinch which can be 1.5-10X the charge voltage of the bank. This means the switches must be crow barred to prevent damage. SCR’s conduct in only one direction so a reverse current shuts them off which can create problems.

Cost: Solid state PF devices exist up to the ~300 kA scale (look up Science Research Lab). The pulse power cost ~$1M at this level with an 8 kV charge and operation at 80 Hz. Scale up is non-linear so a pulse power system at 40 kV and 3 MA is going to cost far more than $10M.

[andrewmdodson]

XRAM pulse generators…?

[asymmetric_implosion]

Similar problem with XRAM. You need switches that can do the job. Opening switch technology at the ~1MA level has not worked correctly using plasma based switching i.e. gas switches. Solid state systems tend to have a problem with the voltage spikes from the switch opening and the pinch. Building large solid state stacks is possible but costly. A single component failure is enough to take out an entire stack. Advanced materials like silicon carbide or diamond might save the day but they are a few years off at least for the systems we are talking about.

[mchargue]

I haven’t noticed this posted before, but it’s an idea for a business that would produce a switch that operates along the same lines. It would need work, though, to increase the current.

http://www.divtecs.com/research/high-current-high-voltage-igbt-switch/

[nyemi]

mchargue wrote: I haven’t noticed this posted before, but it’s an idea for a business that would produce a switch that operates along the same lines. It would need work, though, to increase the current.

http://www.divtecs.com/research/high-current-high-voltage-igbt-switch/

Hi
No IGBT. (Efficiency is small, hot 🙂
I work, plasma ignition.(http://youtu.be/lKwhPeQ0lSg)
I’m using thyristors.

[Breakable]

Thats cool, nyemi.
How many volts/amps do you drive here?

[mchargue]

nyemi wrote:

I haven’t noticed this posted before, but it’s an idea for a business that would produce a switch that operates along the same lines. It would need work, though, to increase the current.

http://www.divtecs.com/research/high-current-high-voltage-igbt-switch/

Hi
No IGBT. (Efficiency is small, hot 🙂
I work, plasma ignition.(http://youtu.be/lKwhPeQ0lSg)
I’m using thyristors.

Any chance you could post more information about the circuit you demoed?

[Author]

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