American Cinematographer - April 2023 - 11

Opposite: From main power, the " distro box " - in this case a 600-amp version -
is one of the first branches for distribution. This page, top: A typical production
has hundreds of feet of high-capacity cable. Larger shows can have multiple
miles of cabling. Bottom: Three views of a 100-amp Bates-type paddle plug. The
three terminals represent hot, neutral and ground connections.
amps it can handle safely. Going beyond
that number can cause a fault
in the system that can lead to fire.
Voltage, while generally a constant,
can drop if the electricity is forced
to travel over a great distance.
To combat this, we usually start
the electrical feed with very large
cables that can not only handle
the high amperage, but also help
reduce the amount of voltage drop
over distance.
The amperage capacity - or
" ampacity " - of these two types of
high-capacity cables is identified as
4/0 (pronounced " four-ought " ) and
2/0 ( " two-ought " ). (See right photo,
page 13.) The higher number represents
a conductor that is capable
of higher amperage.
Typically, wire gauge is an inverse
scale, with the larger number
being a smaller conductor that can
handle fewer amps. For example,
an 18-gauge wire is very small and
can only handle about 5 amps,
while 12-gauge is larger - the size
of stingers that we use every day
- and can handle about 20 or 25
amps. As the numbers get lower,
the conductors get larger and can
handle more amps. After a 1-gauge,
however, the scale flips to x/0, with
larger numerators meaning larger
and higher amperage.
The ampacity of a single length
of 2/0 cable is 300 amps, and 4/0
cable is 400 amps. With 4/0 and 2/0
distribution, there is one cable for
each " leg " of an electrical system:
one for red, black and blue " hot "
legs; one for the white neutral leg;
and one for the ground (which can
be smaller gauge). A 50' length
of 4/0 cable weighs 50 pounds,
so imagine a 400' run of five 4/0
cables and the amount of work it
takes to lay that out!
The terminations on the ends of
4/0 and 2/0 are " camlock " with high
ampacity (generally 400 amps),
and feature plug and socket ends,
with an internal cam post inside
the socket's receptacle. The plug
component has a flat side that
slides past the cam post, and the
plug is then rotated to slide the cam
into a channel machined into the
plug's post - providing a positive
lock that cannot be disconnected
without turning it in the opposite
direction and twisting the cam out
of the channel. This is an important
safety feature that keeps the
connectors in positive contact and
prevents accidental disconnection.
Heavy rubber insulation also makes
the terminations water-resistant.
A plug generally has a protruding
post that is inserted into the
socket's receptacle, with the socket
providing the power and the plug
receiving (designed this way so the
electrified components are always
recessed, ensuring you do not
have an exposed current-carrying
post that can come in contact with
people or objects). With this in
mind, as you lay out cables, you can
always lay out the plug end toward
the power service, which will save
you from having to re-lay your cable
when you attempt to plug it in and
find you've done it backwards. And
in regard to plugging in, the load
end (what you're powering) should
be connected first and then the line
(providing power).
APRIL 2023 / 11
ALL IMAGES COURTESY OF JAY HOLBEN.
American Cinematographer - April 2023

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