Magnet wire of aluminum is a relatively new product; it utilizes EC aluminum. Its cross-sectional area must be 1.6 times that of copper wire to achieve equal direct-current resistance. Although this is a disadvantage in coils where space is a major consideration, aluminum wire has several economic advantages that often outweigh space considerations.
Aluminum conductor weighs half as much as equivalent copper conductor. The lighter weight is attractive for small transformers, coils, motors, and portable equipment, especially in aerospace applications where reduced component weight allows a highly important increase in payload.
Magnet wire of aluminum is a relatively new product; it utilizes EC aluminum. Its
cross-sectional area must be 1.6 times that of copper wire to achieve equal
direct-current resistance. Although this is a disadvantage in coils where space is a
major consideration, aluminum wire has several economic advantages that often outweigh
Aluminum conductor weighs half as much as equivalent copper conductor. The lighter
weight is attractive for small transformers, coils, motors, and portable equipment,
especially in aerospace applications where reduced component weight allows a highly
important increase in payload.
The lower mass of aluminum-wound coils results in lower inertia, improving the
performance of a wide variety of equipment. Low mass simplifies dynamic balancing of
rotary equipment. It also results in higher sensitivity and response in many coil
applications, as in instruments and acoustical devices. Many classes of motors can be
redesigned readily to utilize aluminum magnet wire.
Magnet Strip. With the development of aluminum strip conductors during
the last decade, a new concept in electromagnetic coil design and winding technique has
been exploited. Strip conductor coils can be wound with higher space factors and less
layer-to-layer insulation than coils wound with round wire. With proper selection of
strip insulation and coil design, it is possible to produce an aluminum strip-wound coil
having the same physical dimensions and electrical characteristics as a coil wound with
round copper conductor. The finished aluminum coil may weigh only half as much as the
equivalent copper wire coil. Perhaps the most significant advantage of the aluminum
strip-wound coil is cost.
Generating Systems Equipment
Isolated-phase bus is the most widely accepted
method for connecting generators to transformers. Aluminum bus is cheaper than copper,
and easier to handle and install. Because aluminum conductors are welded easily in the
factory or field, the number of bolted joints needed to install isolated-phase bus
systems is reduced significantly.
Aluminum is used widely for high-voltage switchyard bus, as tubular aluminum conductors
provide a very favorable combination of mechanical and electrical characteristics.
Mechanical Applications. Aluminum’s resistance to corrosion
contributes major economies in condensate storage tanks, because no maintenance is
required inside or outside and no iron is introduced into the boilers. Other
applications of aluminum include control tubing,-tanks, covers, boiler lagging,
jacketing, panels, and canopies.
Power Utilization and Conversion Equipment
The majority of squirrel cage induction motors employ an
integrally cast aluminum rotor. This incorporates the conductor bars, end rings and
cooling fan, eliminating welding or brazing and minimizing the use of bolts, screws
and other pieces typical of assembly. Heat transfer from the conductor bars to the sheet
steel laminations is excellent, minimizing local overheating within the rotor during a
severe overload peak.
The choice of alloy for the rotors depends largely on the operating characteristics
of the motor. A particular rotor design may require an aluminum alloy having a high,
low or intermediate conductivity. Values for rotor alloys range from 60.5% iacs for a
high-conductivity type to 23% for 380-F.
Rectifiers. The major applications of aluminum in rectifier equipment
are electrical conductors, heat sinks, and enclosures.
Aluminum offers several advantages that explain its frequent selection as a heat-sink
material, even though its volume thermal conductivity is less than that of copper. The
extrudability of aluminum permits versatility in the design of aluminum heat sinks with
extended surfaces. Configurations ideal for heat dissipation can be produced economically.
Extruded sections, usually of 6xxx series alloys, can be color anodized to increase
the emissivity of the radiating surfaces, where required by design or service conditions.
An extruded aluminum section often functions both as a heat sink and an electrical
Communications and Electronics Equipment
Aluminum is utilized extensively in radar and microwave
antennas for air-borne and naval electronic equipment, primarily because of its high
strength-to-weight ratio and the rigidity resulting from the large sections permitted.
Structural shapes and large-diameter pipe and tube are used in the supporting structures.
Parabolic reflectors, spun from alloy 1100 sheet, are supported by a frame of extruded or
structural shapes, or pipe. Castings are common for corners, bases and covers.
Virtually all outdoor television antennas are constructed of drawn or welded aluminum tube,
usually in 3003 or 6063 alloy. Aluminum dominates this application because of its
combination of light weight, electrical conductivity and resistance to weathering.