Bias/Manual Control; Summary; Theory Of Operation; Power Supply Circuit - Ametek DPA1 Series Installation, Operation And Troubleshooting Instructions

Phase/AMP Series DPA1/DCPA1
4-22.

BIAS/MANUAL CONTROL.

4-23. The BIAS/MANUAL control is a potentiometer located on the Firing Circuit Module. A +12 V dc is
supplied to one end of the potentiometer and a –12 V dc is supplied to the other end. The wiper of the
potentiometer is connected to the summing point feeding the Summing Amplifier circuit. The function of the
BIAS/MANUAL control is to establish where the PHASE/AMP will turn on with respect to the control signal
input from the process controller. The control may also be used to control the PHASE/AMP when a process
controller is not available.
4-24.

SUMMARY.

4-25. A small control signal input from the process controller (or manual portion of the BIAS/MANUAL
control) will cause a small firing advance of the pulses generated by the SCR Firing circuit. The Pulse Shaper
circuits amplify and extend the firing pulses. Each power SCR is fired late in the half cycle resulting in a small
amount of power being delivered to the load from the PHASE/AMP. Similarly; when the control signal input is
increased, the firing pulses are advanced further in each half cycle, triggering the power SCR's earlier, and
thus increasing the power delivered to the load by the PHASE/AMP.
4-26.

THEORY OF OPERATION.

4-27. The theory of operation of each of the major functional circuits and devices listed below are discussed
in paragraphs 4-28 through 4-55. See schematic diagrams in Section VI during the discussion. Also see
waveforms in Figure 4-6.

Power supply circuit, paragraph 4-28

BIAS/MANUAL control, paragraph 4-30

Summing amplifier circuit, paragraph 4-32

Soft start circuit, paragraph 4-34

Soft start reset circuit, paragraph 4-36

SCR firing circuit, paragraph 4-38

Pulse shaper circuits, paragraph 4-40

Power SCR circuits, paragraph 4-42

Voltage feedback circuit, paragraph 4-44

Optional current limit, paragraph 4-46

Optional heat sink thermostats, paragraph 4-52
4-28.

POWER SUPPLY CIRCUIT

4-29. The DC power supply consists of transformer winding T1
zener diodes DZ2 and DZ3, and resistors R14 and R15.
Rectifiers D1 through D4 form a full wave bridge rectifier. Resistor R15 and filter capacitor C5 filter the output
of the full wave bridge rectifier. Resistor R14, and zener diodes DZ2 and DZ3 provide +12 V dc and –12 V dc
regulated Voltages, respectively. The regulated +12 V dc is supplied to pin 11 on the Summing Amplifier
AMP-1 and to one end of the BIAS/MANUAL control. The –12 V dc is supplied to pin 6 on the Summing
Amplifier and to the other end of the BIAS/MANUAL control. Filter capacitor C5, and zener diodes DZ2 and
DZ3 insure constant supply Voltages during brief line interruptions.
Document 9100030
C
Transformer winding T1
AMETEK HDR Power Systems
, rectifiers D1 through D4, filter capacitor C5,
C
Theory of Operation
Supplies 24 VAC.
25