Here are some Hubbel fuse curves.

http://www.hubbellpowersystems.com/s...rves/30003.jpg

Notice how even the "fast blow" type K types do not clear the circuit under
twice (two times for the Americans = 2x) their rated current level, even
after 5 minutes.

Type K are the fast blow types usually found in better Fluke digital meters
and other sensitive instruments. Other fuses are typically slower than this.

Breakers vary a lot over the years and manufacturer, Most of the cheap panel
ones were thermal and take a lot to trip them out the first time. Then the
rating is not guaranteed and need to be replaced. (read the fine print)
Nobody ever does.

Here is a curve for the thermal magnetic combo units referred to by Lew.
Notice the time curve for long slow overloads starts at 100% as well as the
instantaneous levels at about 800%. Much better protection for you table saw
and other equipment motors.

http://www.sea.siemens.com/us/intern...70A_1-Pole.pdf




"Lew Hodgett" wrote in message
...
Molded case c'bkrs are thermal-magnetic devices.

The magnetic portion monitors the inrush characteristics of the load
which will cause the c'bkr to trip instantaneously if the inrush
current exceeds rating.

OTOH the thermal portion of the device monitors the thermal
characteristics on an inverse time basis.

(The larger the overload, the quicker the c'bkr trips)

There is also a special purpose molded case device known as a "Mag
only" or "motor protector".

These devices are used in 3 phase combination motor starter units and
would have no application in the typical single phase home shop
installation.

Lew




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