Watlow QPAC Modular SCR Power Control Service Bedienungsanleitung PDF herunterladen (Seite 10)

10 WATLOW QPAC Service Manual

Operation Theory, Chapter 3

Q32

Three Phase, Two Leg - Q32

Power Base Operation

The Q32 uses two pair of SCRs connected in inverse parallel to control two lines of

a three phase ungrounded, resistive load. The main board contains the power

supply, the output drivers, connections for the transformer and any of the zero

cross control cards. It is interlocked so that it will not allow any output if a phase

angle card is installed. Q32's will accept 208 to 480 volt transformers as standard.

600 volt units need to be special ordered.

The master portion of the Q32 operates the same as the Q01. Once SCR #2 fires,

transformer T2 receives load voltage and T2B then turns on SCR #4 approximately

60 degrees before zero crossing on L3 phase. As soon as L3 goes negative, SCR

#4 is ON. The next half cycle, SCR #1 is fired, and T2C turns on SCR #3. See

schematic 02-0682 on Page 34.

Power

Supply

FWZ

Control Card

Opto

Slave

Transformer

VAC

3Ø

Heater

Load Circuit

SCR1

SCR2

SCR3

SCR4

Figure 5 -

Q32 Board Layout

Figure 6 -

Q32 Block Diagram

and Typical Load

Circuit

1 2 ... 5 6 7 8 9 10 11 12 13 14 15 ... 42 43

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Watlow QPAC Modular SCR Power Control Service Bedienungsanleitung Seite 10