Harris Broadcast Flexiva FAX 5KW, Техническое руководство

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FAX 5/10/20/30/40KW
October 28, 2013
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888 ‐ 2720 ‐ 001 WARNING: Disconnect primary power prior to servicing. Copyright ©2013, Harris Broadcast
1.12 Grounding Requirements
Two separate ground connections are required for the Flexiva FAX series transmitter: an AC safety ground and an RF
earth ground .
The AC safety ground prevents an electrocution hazard should a dangerous potential from inside the unit
accidentally contact an exposed metal surface. This is done by ensuring all metal surfaces have an uninterrupted
connection back to the physical earth (PE) terminal at the AC mains service entrance. A physical earth (PE)
connection is typically tied to the return current terminal either indoors at the main distribution panel or outside “at
the pole” (as dictated by local codes), thus allowing any fault current to safely return to the power source.
The AC safety ground connection is made automatically for the exciter and other Harris Broadcast auxiliary
equipment via the green/yellow wire on the third prong of the AC input cord. When the exciter and any auxiliary
equipment are connected directly to a user ‐ supplied outlet box or distribution panel, the green ‐ yellow wire from
the AC input cord(s) must terminate at the PE terminal at the AC mains source.
In the case of a Harris Broadcast ‐ supplied AC distribution chassis, the green/yellow earth wire from the incoming AC
mains service terminates at the PE terminal of the AC distribution chassis (ground symbol inside circle). The
individual subassemblies making up the transmitter connect via the green/yellow wire of their mains cords to the
same PE terminal on the AC distribution chassis.
When present, a rack buss ‐ bar will also connect to the PE terminal. Individual panels making up the rack cabinet
without a solid, permanent connection back to the PE terminal that might be exposed to unsafe voltages (e.g. doors
on hinges) will connect to the PE terminal via a wire jumper connection to the buss ‐ bar.
The RF earth ground prevents damage to the equipment during lightning ‐ induced transients and reduces RF
interference to low level circuits in general. An RF ground strap attachment point is located at the rear of the FAX
transmitter and exciter chassis. This connection is suitable for use in a single point grounding system, with the
ground strap attached to the equipment rack and the rack, in turn, to a common grounding plate. A minimum 2"
copper strap is recommended.
Note
Observe this important distinction: The AC safety ground ensures that energy originating at the AC mains
source is always safely returned to the AC mains source (i.e. prevents electrocution), whereas the RF earth
ground ensures that energy “originating in the earth,” such as lightning, safely returns to the earth. Con-
fusion may arise in some cases because the AC safety and RF earth ground circuits may share the same
conductor or connection point(s) in some situations. To prevent confusion, some sources refer to the AC
safety ground as “bonding” and the RF earth ground as “earthing.”
1.13 AC Requirements
1.13.1 Surge Suppression Devices
Harris Broadcast strongly recommends the use of surge protection devices on the incoming AC mains lines. These
devices protect against damages due to transients arising from both natural and man ‐ made sources. (e.g. lightning
and inductive load switching). Clear preference is to be given to “series” type surge protection devices ‐‐ featuring
protection by both a series inductance / shunt capacitor filter and shunt threshold device ‐‐ over simple shunt ‐ only
clamping devices. The surge protector must be sized to handle the full amperage of the load it is protecting (plus a
nominal safety margin) and be connected to the building ground system by short, direct connections. In the case
where the shunt protection elements are protected by a fuse, it is necessary to periodically check the integrity of the
fuse to ensure continued transient protection. Consult the manufacturer of these products for best device to be
used in each installation.
1.13.2 Voltage Regulation
If voltage variations in excess of the transmitter specified range are anticipated, the transmitter power input must be
equipped with an AVR (automatic voltage regulators) (optional equipment) capable of correcting the mains voltage.
There are several factors that need to be taken into consideration when selecting the proper AVR. All these factors
should be discussed with the manufacturer prior to purchasing a unit.