All detector support frame AC power distribution is Class II. Work on AC electrical power distribution will be done in accordance with section 6220 of the Jefferson Lab EH&S Manual. Refer to the current copy of the Jefferson Lab EH&S manual for current lab policy.
The detectors will consume a fair amount of power, between
18kW and 30kW per
spectrometer arm.
The Shield Houses have AC power supplied from an isolation transformer
mounted on the
rear leg of the support gantry. The transformer is on the non-beam dump
side of the gantry.
This clean power is fed to a breaker panel mounted on the lower
electronics platform of the Detector Support Frame. This panel is the
large
one mounted in the middle of the lower
platform. Each relay rack has its own
breaker panel
which is fed from the main panel on the lower
platform. There are thus two
locations which can be used to disconnect AC power to the relay racks.
Both panels
should be checked in the event of a breaker trip. The feed for the
isolation transformer is from a shunt trip breaker in a panel close to
where the beamline enters the hall. The hall fire protection system
will trip this breaker in the event of a fire in the Shield House.
One rack on the gantry platform, beneath the shielding house, has AC power supplied from a breaker in the panel mounted on the lower electronics platform of the Detector Support Frame. This rack houses the VME crate used for the Slow Controls of the spectrometer magnets.
The breaker panels for the two relay racks on the lower platform are located directly adjacent to the racks. They are mounted along the sides of the support frame and are directly accessible by a person standing at the front of each respective relay rack.
The breaker panels
for the three relay racks on the upper platform
are located along the side of the upper platform. They are in front of
their corresponding rack and are accessible to a person standing at
the front of the relay rack.
The breakers in the relay racks' panels control AC power to separate outlet boxes mounted in the rear of the relay racks. Careful attention should be paid to the labeling of breakers and which outlet they correspond to. Within each rack the spatial correlation is not direct.
As a general rule, in the event of a breaker trip the fault should be identified and corrected before AC power is restored to the circuit.
