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The appearance of this plug is sometimes confused with a NEMA 10 connector, rated for 240 V, but the NEMA TT-30 is a 120 V device. The hot and neutral blades are angled at 45° from vertical and 90° to each other, unlike NEMA 10 devices (where the angles are 30° and 60° respectively), also the plug is slightly smaller than a NEMA 10 and ...
120 V circuits are the most common, and used to power NEMA 1 and NEMA 5 outlets, and most residential and light commercial direct-wired lighting circuits. 240 V circuits are used for high-demand applications, such as air conditioners, space heaters, electric stoves, electric clothes dryers, water heaters, and electric vehicle charge points.
Lighting and general purpose receptacles are at 120 volts AC, with larger devices fed by three wire single-phase circuits at 240 volts. In commercial construction, three-phase circuits are often used. Common 3 phase configurations within a building are 208v/120 wye, 120/240 center tapped delta and 480v/277v wye. Lighting is usually fed by 277 V ...
These are used for both 220-volt and 127-volt regions of the country, despite the IEC 60906-2 recommendation that NEMA 5-15 be used for 120 V connections. There are two types of sockets and plugs in NBR 14136: one for 10 A, with a 4.0 mm pin diameter, and another for 20 A, with a 4.8 mm pin diameter. [36]
The hazard of this is that if single phase loads are connected to the high leg (with the connecting person unaware that leg is higher voltage), excess voltage is supplied to that load. This can easily cause failure of the load. Commonly there is a high-leg to neutral load limit when only two transformers are used. [6]
NEMA (National Electrical Manufacturers Association) contactors and motor starters are rated by sizes. These sizes are grouped by rated current and power. [1] [2]
Voltage rating and other characteristics are represented by a colour code (in three-phase plugs the stated voltage is the phase-phase voltage, not the phase-neutral voltage). Plugs have the earth pin of a larger diameter than the others, and located in different places depending on the voltage rating, making it impossible to mate, for instance ...
The cable connectors and sockets are keyed and colour-coded, according to the voltage range and frequency used; common colours for 50–60 Hz AC power are yellow for 100–130 volts, blue for 200–250 volts, and red for 380–480 volts. The blue fittings are often used for providing weather-proofed exterior sockets for outdoor apparatus.