Current Technology Selenium Surge Suppression Demonstration

Used as a semiconductor in rectifiers and suppressors for many years, selenium occurs naturally on the
earth. Its popularity as a rectifier is fading in favor of its silicon equivalent. However, demand for
selenium suppressors continues.
Depositing the elements on a metal substrate's surface produces selenium cells. This provides the cells
with good thermal mass and energy dissipation as well as self-healing characteristics, allowing the
device to survive energy discharges in excess of the rated value. Selenium's crystalline structure gives it
the ability to continue functioning after a burst of energy in excess of its short pulse width rating. Its
suppressor operation is comparable to a pressure relief valve — when the pressure rises, the relief valve
opens, releases the pressure, and then resets itself.
Because of its unique properties, the selenium suppressor remains viable in many applications. Special
clamping capabilities enable the selenium suppressor to find its own niche as a transient voltage
suppressor. Because of its ability to continuously dissipate power and handle long surges, it's better
than MOVs or silicon suppressors for some applications.
The selenium suppressor can absorb energy levels in excess of its rated capability while maintaining its
clamping characteristics on the next cycle. The layering of the suppressor onto the aluminum plate
allows the suppressor's energy capabilities to follow that of a heat sink curve. This heat sinking
capability allows steady-state power dissipation up to 40 times that of an MOV. For a 130V suppressor,
the selenium product allows steady-state dissipation of 2.5W to 80W, compared with an MOV that
allows only 0.1W to 2.5W. Fig. 1 shows several selenium cells.
Manufacturers produce selenium suppressor cell plates in sizes varying from 1 in.×1 in. to 12 in.×16 in.
that can function at a temperature of 0°C to 55°C ambient without any derating. The voltage of a
selenium suppressor cell starts at 26Vrms or 22.5Vdc per cell plate. Users must keep the suppressor to a
75V maximum due to the dielectric ceiling of the cell. The capacitive nature of the plate allows
placement in series to attain higher voltage levels.
Other suppressors can handle high current, short pulse widths in the microsecond range, but the
selenium suppressor can handle millisecond pulse width currents, making it a more robust suppressor
than silicon devices. It has a typical response time of less than 1 ms and is capable of handling pulses
with long decay times as seen in large dc motors or any inductive loads with L/R ratios in the 100 ms
range.
Power conditioning systems, generators, and ac controllers are typical selenium suppressor
applications. Suppressor applications are specifically used on the dc side of a rectified generator output,
across SCRs on large controllers, across dc motors, and on transformers for line-to-line transient
suppression.

Category:

Science & Technology

Tags:

• Transient Voltage
• Surge
• Overvoltage
• arc flash

[runningformoney]

this is a useless video no joke

[mrmrmrohm]

Are you familiar with Surge Protection Devices?

[wrestleorsurf]

@mrmrmrohm whats that

[mrmrmrohm]

@wrestleorsurf a Surge suppression device to protect critical equipment in the event of a power surge or temporary over voltage condition.

[leolearn713]

This is very deceptive. There are many things wrong with this test. The MOV leads are too long, the terminology this guy is using is deceptive in and of itself. A surge lasts microseconds - not "half a second" - maybe in the third world somewhere - that may be possible - and then you could call it a temporary overvoltage. Selenium cells are completely obsolete in the surge protection field as a primary component in power protection and there's a reason for it.

[notentirelysure85]

Oh no! in Australia it's 240 volts the whole time! I must unplug everything

[Doppelgangergang]

This just goes to show that the classic MOV used in surge suppressors don't actually start kicking in until the voltage reaches a very high voltage that is potentially dangerous for the "protected" equipment.

The only advantage I see in using MOV-only surge supressors is - guess what - they're cheap!