Schneider's Telemecanique engineers have just changed the venerable motor starter by combining overload and overcurrent protection—a contactor with a breaker. The move saves on space and wiring.
A contactor opens and closes pairs of metal points that switch the motor off and on. It's what ultimately closes when an operator pushes a start button. It's also what opens when an overload relay detects too much current flowing to the motor, as happens when the load the motor is driving jams. Contactors open and close many times in their lives.
A breaker (or fuses) protects against the heavy rush of current that strikes a motor during a short circuit. Short circuits are rare but very destructive. Basically, the breaker is another set of contact points similar to those on the contactor, albeit ones that operate rarely. When they do, they must open swiftly and with certainty under what can be metal-melting amps.
Contactor contacts have to be heavy enough to tolerate repeated closings, while breaker contacts have to be light enough to open fast: two seemingly disparate requirements. Until now, that's how you got them, as two separate parts.
Telemecanique's U-Line motor starters combine both sets of contacts into one. To users, that means the starter takes up less space. There's no wiring to run between breaker and contactor either, saving labor. Compared with conventional units, the new starters use about 80 percent less space and require about 60 percent less installation time for about the same price.
Why did it take 100 years to do something this obvious? Part of the story, according to Schneider Marketing Director Charles Forsgard, was how Telemecanique engineers figured out a way to separate the electromagnets that drive the moveable contacts from the contacts themselves, reducing their inertia. The other part of the story is in the sophisticated metallurgy that compose the contacts to keep them from welding closed. "It's more than just plated copper," Forsgard says. The formula is a secret, of course.
Contact:Charles Forsgard, Schneider Electric