Ametek Sorensen DC Series, Руководство по эксплуатации

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Theory of Operation Sorensen DCS-E Series 3kW Supplies
5-12 M362295-01 Rev D
O
VER
V
OLTAGE
P
ROTECTION
(OVP) C
IRCUIT
The OVP circuit protects the load connected to the power supply from over-voltage conditions
arising from programming errors, incorrect voltage control adjustments, or power supply failure.
The OVP circuit monitors the output voltage and activates the internal shutdown circuit of the
supply whenever the output exceeds a selected trip limit. Op amp U7-A monitors the output
voltage of the supply at pin 3 through the divider formed by resistors R1 and R84. When the
voltage at pin 3 rises above the trip point reference at pin 2, the output of U7-A goes high
activating the internal shutdown circuit through diode CR20. Resistor R82 and diode CR22 latch
the OVP circuit ON after it has been activated. Resetting of the circuit (after correcting the
cause of the original activation) is accomplished by cycling the power supply OFF and then ON
to release the latch. It can also be reset by using the front panel standby switch or by activating
the remote shutdown function. Using standby or remote shutdown will also reset the OVP by
pulling reference pin 2 high through diode CR21.
The 0-5V reference trip limit, at pin 2 of U7-A, can be set using the front panel potentiometer,
using 0-5V or 0-10V analog remote programming signals, or through the optional IEEE-488
programming card. Switch SW1-7 is used to select either local (switch CLOSED) or remote
(switch OPEN) programming. With SW1-7 CLOSED and SW1-6 OPEN, the trip level is set by
the front panel OVP potentiometer. To use remote analog programming, switch SW1-7 is set to
OPEN, disconnecting the front panel input, and the programming source is connected to J3
connector pin 3. Switch SW1-6 is used to select the programming scale: 0-5V with the switch
OPEN or 0-10V with the switch CLOSED.
R
EMOTE
S
HUTDOWN
C
IRCUIT AND THE
F
RONT
P
ANEL
S
TANDBY
S
WITCH
The remote shutdown circuit and the front panel standby switch are used to disable the output
of the supply without shutting off the entire supply. The function can be used when making
changes to either the load or to power supply settings or as part of remote startup/safety
interlock circuits. The standby switch and the remote shutdown function can also be used to
reset the OVP circuit after it has been activated. The remote shutdown circuit accepts 12-250
Vac, 12-130 Vdc ,or TTL compatible inputs, while the front panel standby switch provides local
access to the shutdown circuit.
The remote shutdown circuit is made up of optocoupler U9, NAND gates U8-A and U8-B,
switch SW1-8, transistor Q6, and their related components. Switch SW1-8 is used to select
either positive or negative logic for the remote input signal. With the switch OPEN, the circuit
uses positive logic so that a high input disables the output of the supply. With the switch
CLOSED, the circuit uses negative logic so that a low input disables the output. Optocoupler U9
isolates the programming input from the supply, allowing the use of programming sources with
a voltage differential of up to 400 Vdc with respect to the output. NAND gates U8-A and U8-B
provide the required logic for the various inputs. The output of U8-B controls transistor Q6
which activates the internal shutdown circuit of the supply through diode CR19 when it is ON.
The high signal which activates the shutdown circuit also illuminates the front panel shutdown
(S/D) LED
through pin 14 of connector J1. Resistor R101 provides the IEEE-488 monitor signal.
Diode CR24 rectifies AC inputs to the optocoupler. Diode CR25 protects against reverse
polarity TTL signals.
The front panel standby switch shuts down the supply by putting a high signal on the S/D
LED line which activates the internal shutdown circuit through diode CR19 and turns the front
panel indicator LED ON.