9/15/06
888-2586-001
4-29
WARNING: Disconnect primary power prior to servicing.
Section 4 Overall System Theory
Platinum Z16HD+
•
-20Vdc
•
+10Vdc
These voltages are sent to the Rectifier boards where they are regulated before being
sent on to the controller boards.
The board contains 3 relays, A19K1, A19K2 and A19K3. When the transmitter is
turned on, A19K1 activates the main contactor (simply called K1) which then applies 3
phase AC to the PA power Supplies, while A19K2 applies AC to turn on the exciter(s).
A19K3 selects the low or high fan speed by actuating the fan speed select relay K2
which is mounted next to the main AC contactor.
4.6
Detailed Power Supply Descriptions
4.6.1
3-Phase PA Power Supply
Refer to the Overall System Block Diagram in the schematic package for the following
discussion. The transmitter 3 phase AC inputs connect directly to K1, the AC mains
contactor. The transformer side of the contactor is wired in parallel to power
transformers T1, T2, T3 and T4 primaries in the bottom of the transmitter. The
transformer primaries are wired according to the type of AC input, 3 wire or 4 wire, and
must be tapped for the proper AC input voltage. The tapping chart can be found on the
Overall System Block Diagram.
Each transformer has 2 WYE secondaries with the center connection being the rectified
DC output of 52Vdc (nominal). Note that the secondaries are the same no matter what
the AC input voltage or configuration. The two secondary outputs are combined via
large inductive chokes L1-L8. C1, C2, C5 and C6, 120,000uF filter caps, provide the
final filtering.
Each of the transformer secondary taps is connected to a Rectifier Board. The
secondaries use the unique tap switching design to give a small window of coarse
regulation (approximately 2Vdc change per tap) from 48 to 54Vdc to compensate for 3
phase AC line variations.
4.6.1.1
Rectifier Board
The Rectifier Board contains the SCRs which are used for the tap switching,
rectification of the 3 phase AC and to turn the supplies on and off. Each secondary
winding has four taps, see Figure 4-13. Each of these taps have one SCR to ground. The
Power Supply Controller can turn on any one of the four SCRs, on each winding, at a
given time. If the voltage is not high enough at the DC output, the PS Controller can
change the transformer turns ratio by turning on a different SCR and therefore utilizing
Содержание Platinum Z16HD+
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