The Motor's Best Friend

Written by Thomas Yoon

Continued from page 1

For reliable operation,repparttar overload relay must be located atrepparttar 133328 same temperature environment asrepparttar 133329 motor. The heating effect of repparttar 133330 bimetallic strip mechanism is supposed to representrepparttar 133331 heating ofrepparttar 133332 motor windings.

Melting alloy overload relays calibrated byrepparttar 133333 manufacturer are consideredrepparttar 133334 most reliable of allrepparttar 133335 thermal overload protective devices. However, more commonly used isrepparttar 133336 bimetallic overload relays becauserepparttar 133337 tripping current setting can be adjusted.

Allrepparttar 133338 overload relays have one major limitation - because they operate on line current, they do not directly senserepparttar 133339 motor temperatures. For normal steady running conditions, this poses no problem at all.

However, when a motor starts and stops frequently,repparttar 133340 relay may not completely protectrepparttar 133341 motor. Why is that so?

Duringrepparttar 133342 motor running,repparttar 133343 relay temperature followsrepparttar 133344 motor temperature closely. Whenrepparttar 133345 motor is off,repparttar 133346 relay tends to cool off at a faster rate because of its lower mass. After a number of starts and stops,repparttar 133347 temperatures ofrepparttar 133348 relay andrepparttar 133349 motor may drift further and further apart. Eventuallyrepparttar 133350 motor becomes hot, and yetrepparttar 133351 relay does not trip because it is still cool. The motor burns.

Frequent starting and stopping of motors is no good both electrically and mechanically.

Until next time...

Are You Stumped by Complicated Electrical Calculations? Useful Electro-Technology Questions & Answers available for all electrical installations.

Many years of working experience in Marine, Facilities, Construction has given the author material for writing e-books and articles related to engineering, and management. Subscribe to facworld ezine More information at Life on Ships and Mechanical Engineer

Wi-Fi Is Out There and Spreading Fast

Written by Anton Komarov

Continued from page 1

As an Angeleno who lives with real threats like smog, gang warfare, earthquakes, wildfires, landslides and rush-hour traffic, I decided to fully embracerepparttar Wi-Fi movement. I wanted to be one of those happy people plucking away on laptops at Starbucks Latest News about Starbucks or Borders in between sips of cafe Americanos. So I called up Terry Halberg, telecommunications planner forrepparttar 133327 city of Los Angeles, to get me started with a personal tour ofrepparttar 133328 Van Nuys community Wi-Fi zone. To prepare, I boughtrepparttar 133329 cheapest wireless modem card I could find for mylaptop Latest News about laptop - $20 at Fry's.

The city's free Wi-Fi network itself is not much to look at. It's as visual as radio. There's not much to see other thanrepparttar 133330 Wi-Fi routers placed strategically inside meeting rooms and out on utility polls onrepparttar 133331 streets surroundingrepparttar 133332 MBSFVCSC. The routers are no bigger than a hardback Jackie Collins novel, with two antennas on top and two onrepparttar 133333 bottom.

"It looks like a little robot guy," Halberg said. They beamrepparttar 133334 signal all aroundrepparttar 133335 area and intorepparttar 133336 computers of anyone who wants to access it.

Anyone with a laptop or PDA Latest News about PDAs with wireless capability (such as my $20 card) can plop down anywhere aroundrepparttar 133337 Van Nuys Civic Center/ Courthouse complex and log on for free torepparttar 133338 community network. Becauserepparttar 133339 city is providingrepparttar 133340 service, users must start at a registration page and agree not to userepparttar 133341 network to do illegal things such as download child porn or sell unregistered firearms to Third World countries, and not to sue if you get hacked while online.

Logging intorepparttar 133342 Wi-Fi Community Network hooks users up not just torepparttar 133343 network but with anyone else using it. This brings up more disturbing questions such as, if my computer can pick up data from these Wi-Fi waves, can data be sucked out of itrepparttar 133344 same way?

Yes, it can.

According torepparttar 133345 nonprofit Wi-Fi Alliance's Web site: "If your transmissions are not secure, you takerepparttar 133346 risk of others intercepting your business e-mails, examining your corporate files and records, and using your network and Internet connection to distribute their own messages and communications."

In other words, people can peek on what you're looking at online as if they were looking over your shoulder. That might not bother Net surfers who limit their online travels to sites such as or, but most people want their Internet experiences to be private. If that'srepparttar 133347 case, dial-up may still berepparttar 133348 way to go until there's improved security Latest News about Security for Wi-Fi networks. That probably won't be too long. This revolution is spreading in months, not years. And though it may not be televised, it is definitely coming to a screen near you.

A cisco certified engineer. Working in Wi-Fi area in Russia. Chief master of wi-fi resourse.

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