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NEMA (National Electrical Manufacturers Association) contactors and motor starters are rated by sizes. These sizes are grouped by rated current and power . [ 1 ] [ 2 ]
NEMA contact ratings are how much current at a rated voltage a relay or other pilot device can switch. The current rating of smaller NEMA contactors or their auxiliaries are defined by NEMA ICS 5: Industrial Control and Systems, Control Circuit and Pilot Devices [1] standard. The nomenclature is a letter followed by a three-digit number, the ...
All NEMA 5 devices are three-wire grounding devices (hot–neutral–ground) rated for 125 V maximum, with the 5-15, 5-20 and 5-30 being grounded versions of the 1-15, 1-20 and 1-30, respectively. The addition is a 3 ⁄ 16-inch (4.8 mm) diameter round or U-shaped ground pin, 1 ⁄ 8 in (3.2 mm) longer than the power blades (so the device is ...
Each type specifies characteristics of an enclosure, but not, for example, a specific enclosure size. Note that higher numbers do not include the lower-numbered tests. For example, types 3, 4 and 6 are intended for outdoor use, but type 5 is not. A NEMA enclosure rating does not mean that it also meets the same UL enclosure rating. [2]
The service factor is typically in the 1.15-1.4 range, with the figure being lower for higher-power motors. For every hour of operation at the service-factor-adjusted power rating, a motor loses two to three hours of life at nominal power, i.e. its service life is reduced to less than half for continued operation at this level.
The 1893 GEC Catalogue included three sizes of what was described as Double plug Sockets with capacities described not in amps, but as "1 to 5 lights", "5 to 10 lights" and "10 to 20 lights". These were clearly recognisable as two-pin plugs and sockets, but with no indication as to pin size or spacing, they were sold as pairs.
Volume 3: Circuit-breakers, circuit-breakers, switch-disconnectors and switch-fuse units Volume 4-1: Contactors and motor starters; electromechanical contactors and motor starters[1] Volume 4-2: Contactors and motor starters - Semiconductor motor controllers and starters for a.c. voltage
In this system, the primary distribution network supplies a few substations per area, and the 230 V / 400 V power from each substation is directly distributed to end users over a region of normally less than 1 km radius. Three live (hot) wires and the neutral are connected to the building for a three phase service. Single-phase distribution ...