Q&A: ‘Thyristors’ are for BART Trains and Particle Accelerators, Too

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When a Mar 16 voltage swell infirm dozens of sight cars on a San Francisco Bay Area’s busiest rail movement system, a sight components that were blown out by a surge—called “thyristors”—leapt into a region’s lexicon, appearing in media coverage and amicable media posts.

A Bay Area Regional Transit (BART) sight pulls into a station. In March, Dozens of BART cars were temporarily put out of use when an electrical swell caused a disaster of inclination called “thyristors.” Thyristors have a far-reaching operation of applications, and have been used for decades in molecule accelerators during Berkeley Lab. Image credit: Flickr/Eric Fischer around Creative Commons

A Bay Area Regional Transit (BART) sight pulls into a station. In March, Dozens of BART cars were temporarily put out of use when an electrical swell caused a disaster of inclination called “thyristors.” Thyristors have a far-reaching operation of applications, and have been used for decades in molecule accelerators during Berkeley Lab. Image credit: Flickr/Eric Fischer around Creative Commons

BART (Bay Area Rapid Transit) engineers and outward experts have been operative in a weeks given to solve a electrical problems and revive normal use along one coax of a rail system, and a movement group systematic a new collection of a palm-sized BART sight thyristors, that resemble puck-shaped hint plugs with a spin ceramic bombard and prosaic steel contacts during possibly end.

Thyristors (pronounced THIGH-rist-ors) aren’t only for trains, though. They have been around for decades and are a workhorse for many appetite acclimatisation and switching applications. They are stout electrical switching inclination that can hoop a lot of voltage and stream relations to their size, with applications trimming from light dimmers to molecule accelerators.

In this QA, Will Waldron, a high-voltage and pulsed-power operative during a Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab), describes how thyristors have been used for decades in a accumulation of ways to keep high-power investigate machines using during Berkeley Lab.

Q: What are thyristors?

A: Thyristors are semiconductor or “solid-state” switches grown in a 1950s to reinstate opening and gas-filled tubes. They are ideal for power-conversion applications that mostly need high-power switching. A thyristor can offer as a elementary electrical switch between a transformer or a charged capacitor and a bucket that consumes electrical power. Thyristors enclose a silicon chip that allows them to spin on with an electronic trigger­.

Thyristors are really economical, yet tradition thyristors designed for aloft opening can be some-more costly.

Examples of thyristor forms that have been used during Berkeley Lab. The palm-sized thyristor during bottom left is an instance of a standard device, with red and white trigger wires. On a right, a thyristor (middle) is mounted between dual steel feverishness sinks, that control feverishness divided and assistance cold a device during high-power operation. Image credit: Roy Kaltschmidt/Berkeley Lab

Examples of thyristor forms that have been used during Berkeley Lab. The palm-sized thyristor during bottom left is an instance of a standard device, with red and white trigger wires. On a right, a thyristor (middle) is mounted between dual steel feverishness sinks, that control feverishness divided and assistance cold a device during high-power operation. Image credit: Roy Kaltschmidt/Berkeley Lab

Q: What is a story of Berkeley Lab’s use of thyristors?

A: Pioneering work during Berkeley Lab in a late 1970s and 1980s used array and together combinations of thyristors for really high-voltage and high-current electrical switching and for singular power-conversion applications associated to captivating alloy appetite research.

We have found many useful applications for these inclination in molecule accelerators such as magnet appetite reserve and high-voltage pulsers.

In further to many lower-power applications, several vicious high-power magnet appetite reserve during a Advanced Light Source, a Superconducting Magnet Test Facility, and a 88-inch Cyclotron during Berkeley Lab use thyristors for appetite acclimatisation and regulation.

This print shows a thyristor public (the gold-colored, layered structure during middle) that incorporates a thyristor (not visible) between dual feverishness sinks during NDCX-II (the Neutralized Drift Compression Experiment), an ion-beam accelerator during Berkeley Lab. This thyristor switches thousands of amps to a beam-focusing magnets along a NDCX-II beamline. Image credit: Roy Kaltschmidt/Berkeley Lab

This print shows a thyristor public (the gold-colored, layered structure during middle) that incorporates a thyristor (not visible) between dual feverishness sinks during NDCX-II (the Neutralized Drift Compression Experiment), an ion-beam accelerator during Berkeley Lab. This thyristor switches thousands of amps to a beam-focusing magnets along a NDCX-II beamline. Image credit: Roy Kaltschmidt/Berkeley Lab

We are now contrast specialized thyristors during a BELLA (Berkeley Lab Laser Accelerator) Center to reinstate comparison switches formed on gas-filled tubes famous as thyratrons. This should assistance revoke timing jitter and boost switch lifetime to advantage destiny applications of laser plasma accelerators.

Q: What complicated inclination are now replacing thyristors?

A: Insulated embankment bipolar transistors, or IGBTs, and steel oxide semiconductor margin outcome transistors, or MOSFETS, are most faster than thyristors, though they are some-more costly and are some-more singular in their appetite ratings.

Currently accessible IGBTs can hoop high power, and a cost is entrance down. Many appetite acclimatisation and pulsed appetite applications that need a fastest switching speeds have changed from thyristors to IGBTs and MOSFETs to urge performance.

Q: What are common causes of thyristor failure?

A: Over-voltage conditions and switching stream too quickly.

Q: What other inclination can be joined to thyristors to raise their efficacy and/or lengthen their life?

A: Various combinations of resistors, capacitors, diodes, and metal-oxide varistors are used to conceal voltage transients and strengthen a device from extreme voltage. Series fuses and inductors can be used to strengthen a device from extreme stream and to extent a arise in current.

In some pulsed-power applications, we mostly rest on a array array of thyristors, that together can reason off a voltage most aloft than a voltage rating of a singular device. For these applications, safeguarding any device from extreme voltage is critical.

In other applications we are pulling a inclination to switch stream fast and we have to make certain that a specifications of a switch are not exceeded.

Source: LBL