Last year, a solar power farm in the United Kingdom had a really bad day and blew one of the main fuses on its three-phase AC output feed. (If you work it out, this phase had a maximum power of 2.25 megawatts.) An engineer sent the blown fuse to Big Clive, who proceeds in the following video to find out what’s inside with the cheap-o X-ray device, how it works, and what the aftermath of a blown fuse event looks like. Cameo appearance by an ever-helpful cat.
The fuse is rated to break a short-circuit current of 40,000 amperes. The 36 kV rating is between phases, with 20 kV above ground.
One of my favourite YouTube channels is bigclivedotcom, who tears down and reverse-engineers electronic and other gadgets, often discovering horrors, occasionally deadly, in shoddy products mostly from China. Yesterday, he posted a delightful analysis of a fine piece of Chinese junk, a “shake flashlight”, which is supposed to generate its own power by shaking the object in your hand.
Shake flashlights are a “green” gimmick which have been around for some time: here is an example of one for sale at Amazon. They appeal to eco-freaks (no batteries!), the gimmick-obsessed kind of survivalist, and people who can’t solve simple problems in electromagnetism. In the usual design, the body of the flashlight contains a tube inside which a powerful permanent magnet is free to slide back and forth. A coil with many turns of wire is wound around the centre of the tube, and there’s usually two magnets fixed to the ends of tube which repel the moving magnet as it approaches them, reversing its motion without impact. When you shake the flashlight, the moving magnet passes back and forth through the coil, inducing a pulse of current each time the magnetic field passes through its windings. This current is then rectified (since its polarity alternates depending on the direction of the magnet’s motion) and stored in either a super-capacitor or rechargeable battery which, when the light is turned on, drives a light-emitting diode (usually a relatively dim low-power device that doesn’t draw much current).
The idea is that you can keep one of these flashlights, say, in you car’s glove compartment for roadside emergencies and never have to worry about dead batteries when you need it: just a few shakes and fiat lux. In practice, like most “green” products, it doesn’t work very well. It takes a whole lotta shakin’ to generate much charge, so unless you do something like put it in a paint mixer, you only get a few minutes of dim light before it goes out.
But count on the Chinese to take it to the next level. I won’t spoil the fun you’ll have viewing the following video.
Do you have any examples or memories of fake products? I recall the “Affordable Care Act”.