Prefect's Pages.. Publications .. IQP .. Power Distribution Boxes

A given theatre production will often call for many types of devices to be connected to the power source. Some of these devices, such as dimmer racks, are usually fitted with high-capacity power connectors such as Cam-Loks. This makes sense, as a rack of dimmers has the potential to draw a large amount of current. However, other devices such as small dimmer modules, chain motors (used for lifting lighting trusses and speakers), audio amplifiers, and other equipment tend not to connect directly to Cam-Loks. This is where power distribution boxes (distros) come in handy.

A distro takes a high-capacity or medium-capacity power feed and splits it into several lower-capacity feeds. For example, distros that have have three-phase Cam-Loks for inputs and several edison, twist-lock, and other types of outputs are frequently found. Sometimes larger distros will have medium-capacity feeds on them, such as MDS connectors.

**Figure 7.4:** A power distro with several types of outputs. Three phase Cam-Lok connectors feed the tap. Several circuits are wired from these, providing single-phase twist, edison and MDS circuits as well as three-phase twist-lock circuits.
$\begin{figure}\psfig{file=power/pwrtap1.eps}\end{figure}$

Most distros provide circuit breakers, much like permanent power panels. These are to protect from current overload on the low-capacity circuits. Again, they also provide convenient switches for enabling and disabling circuits, which can be very useful for safety at times. It is common practice to disable circuit breakers for dangerous equipment such as chain motors when the equipment is not being used. When a lock is applied to the front cover of the distro it makes it difficult for those who are not authorized to use equipment.

**Figure 7.5:** A small power distro fed by an MDS feed. One phase provides about 60 amps of current, divided into several edison and twist-lock circuits.
$\begin{figure}\psfig{file=power/mdsdist1.eps}\end{figure}$

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