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Theory of Operation
Phase/AMP Series DPA1/DCPA1
4-3.
In the DPA-1 PHASE/AMP, two SCR's are used back-to-back, in series with the line as shown in
Figure 4-3. This method of connecting the SCR's allows full wave rectification of the input Voltage in lieu of
half wave rectification that would occur with a single SCR as shown in Figure 4-1. When SCR1 is gated by a
Voltage applied between the gate (G
) and the cathode (K
), it turns on (fires), permitting current to flow
1
1
through load Z
during the positive half of the input Voltage. When SCR2 is gated, current is permitted to flow
L
through load Z
during the negative half cycle of the input Voltage. Thus by controlling the instant of gating,
L
the conduction angle, and consequently, the power delivered to load Z
can be controlled. Figure 4-4 shows
L
the current flow through the SCR's and load Z
for the positive and negative half cycles of the input Voltage.
L
Figure 4-3 SCR's Connected Back-to-Back to Obtain Full Wave Rectification
Figure 4-4 Current Flow Through Back-to-Back SCR's and Load
22
AMETEK HDR Power Systems
Document 9100030
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