Download CONTROL INTERLOCK AND MONITORING SYSTEM FOR

CONTROL INTERLOCK AND MONITORING SYSTEM FOR 80 KW IOT
BASED RF POWER AMPLIFIER SYSTEM AT 505.812 MHZ FOR INDUS-2
Gautam Kumar*, R.K. Deo, M.K. Jain, Sunil Bagre, P.R. Hannurkar;
RRCAT, Indore –452013, INDIA,
Abstract
For 80 kW inductive output tube (IOT) based RF power
amplifier system at 505.812 MHz for Indus-2, a control,
interlock and monitoring system is realized. This is to
facilitate proper start-up and shutdown of the amplifier
system, monitor various parameters to detect any malfunction during its operation and to bring the system in a
safe stage, thereby assuring reliable operation of the
amplifier system. This high power amplifier system
incorporates interlocks such as cooling interlocks, various
voltage and current interlocks and time critical RF
interlocks. Processing of operation sequence, cooling
interlocks and various voltage and current interlocks have
been realized by using Siemens make S7-CPU-315-2DP
(CPU) based programmable logic controller (PLC)
system. While time critical or fast interlocks have been
realized by using Seimens make FPGA based Boolean
Co-processor FM-352-5 which operates in standalone
mode. Seimens make operating panel OP277 6” is being
used as a human machine interface (HMI) device for
command, data, alarm generation and process parameter
monitoring.
separate isolated cabinet called HV deck. This in turn
demands the high voltage isolation signal conditioning
unit (SCU) to reproduce the sense voltage and current
signals of auxiliary supplies at ground potential. Rated
beam current is 3.3 A operated in class AB mode with
quiescent current about 100 mA and there is no body
current in this IOT amplifier system. The solenoid supply
(7 V, 25 A typically) is needed to focus the electron beam
travelling from cathode to collector, this supply is used at
ground potential. Forced air cooling (3 cubic
meter/minute, 2 kPa) is used for the cooling of electron
gun and cavities of IOT tube, however collector & body
of IOT tube are water cooled (50 lpm, 270 kPa) by low
conductivity water (LCW). The arc detection and RF
monitoring system is also incorporated with control,
interlock and monitoring system. The high power IOT
based amplifier system has been tested up to 50 kW RF
power level. The set up is shown in figure 2 with its
subsystems marked by number 1,2, 3,4 and 5.
OVERVIEW OF IOT AMPLIFIER
SYSTEM
80 kW IOT is a linear tube based hybrid device
having partial features of triode tube and klystron.
Figure 1: Internal structure of IOT tube.
To achieve high power RF amplification biasing
of IOT tube with high voltage (HV) (-36 kV rated but
most of the test have been carried out at -32 kV) is
needed. This high voltage will appear across the cathode
and collector of the amplifier tube, where the collector
remains at ground potential. Structure of IOT tube is
shown in figure 1, this amplifier has electron gun
auxiliary supplies floating at cathode potential -32 kV,
namely, filament power supply (7.25 V, 25 A), sputter ion
pump supply (4.5 kV, 1-2 µA), control grid power supply
(-300 to -80 V, < 1 mA), these supplies are mounted on
Figure 2: 80 kW IOT power amplifier system set up of
Indus-2, here cabinet no. 1 is control, interlock and
monitoring system, 2 is HV deck with optical isolation
SCU, 3 is High power IOT amplifier, 4 is LCW cooling
system and 5 is air blower.
CONTROL, INTERLOCK AND
MONITORING SYSTEM REQUIREMENT
The high power amplifier is intended primarily
for unattended operation under automatic or remote
control.
The control system controls the start-up
sequence and maintains continuous surveillance over the
operation of the equipment. This amplifier system needs
to be switched on in a predefined sequential manner for
the safe and reliable operation i.e. the first step is heating
of filament called black heat mode (B_H) (stage I).
Second step of filament heating is called standby (S_B),
at this stage (stage II) cathode is ready for electron
emission. In third step transmit (Tx) command is issued
(stage III) to put on high voltage. After attaining -32 kV
system issues an HV ready command (digital o/p) so that
RF input can be given to IOT amplifier (stage IV). This
control logic flows one by one in sequential manner from
first stage to fourth stage.
Voltage and current values of the auxiliary and
focussing supplies have safe operating range. In this range
the operation of IOT is normal and safe. If any value goes
out of the safe range IOT amplifier system should be
tripped or taken back to previous safe stage as defined in
the control system program. Similarly there are several
other interlock signals incorporated which have been
processed and monitored continuously e.g.: coolant
temperature interlocks; flow rate interlocks; beam voltage
and current sense interlocks; door interlock etc. This
interlocks are comparatively slow (execution time is of
the order of ms). There are fast interlocks (execution time
is of the order of few µs) such as RF excess input drive
and excess RF output reflected signals, IOT and circulator
arc.
The monitoring system is needed to generate
command signals and display set, read back and status
signals of the power supplies flow switches and also
display value of RF input (i/p), output (o/p) power and
VSWR. This system should also takes care of alarm
generation and fault logging.
EMPLOYED CONTROL DEVICES
programmed by using Simatic Manager V5.4 incl. SP5
software. Language used for programming is function
block diagram (FBD) language. While the Arm controller
based HMI is programmed by using Simatic WinCC
Flexible 2008 SP2 software. PLC and HMI communicates
via MPI cable by serial transmission while PLC and
FM352-5 is interfaced via simple wire cable as shown in
figure 5.
Table 1: Specifications of employed devices
S
N
1
2
3
4
4
5
6
7
8
9
Device Name & Model
Number
CPU315-2DP
6ES7-315-2AG10-0AB0
Digital input (DI) module
SM321-7- BH01-0AB0
No. of
Channels
-
Signal levels
16
--do as-Digital output (DO)
module SM322-1BH010AA0
--do as-Analog input (AI)
module SM331-7KF020AB0
--do as-AI SM331-7HF01-0AB0
Analog output module
SM332-5HF00-0AB0
FM352-5, 6ES7-3525AH00-0AE0
-do as-do as-
Logic 0
(-30 to 5 V),
Logic 1 (13
to 30 V)
--do as---do as--
-
-do as8
--do as-4-20 mA
current
8
8
8
-do as0-10 V
0-10 V
11 DI,
8 DO
Logic ‘0’
same as DI &
‘1’ (11-30 V)
To generate control logic start-up sequence and
slow safety interlocks CPU 315-2DP has been used with
its S7-300 series digital and analog i/p, o/p modules as
shown in figure 3. The high speed Boolean co-processor
function module FM 352-5 is used to control and process
all the fast interlock signals. It is FPGA based control
system having digital i/p and o/p channels. CPU is
connected to its input and output (I/O) modules via
backplane bus. CPU and all the I/O modules and FM 3525 are operated by 24 V dc supply. All the devices of
figure 3 are specified in table 1.
Figure 4: Employed HMI device OP277 6” in IOT
amplifier system.
SCHEME OF CONTROL SYSTEM
Figure 3: Employed PLC system and high speed Boolean
coprocessor FM 352-5 in IOT amplifier system.
FM352-5 (shown in figure 3 and also refer 9
number of table 1) and HMI Op 277 6” (6 inch) (shown in
figure 4) is running independent from CPU. The arm
controller based Op277 6” is a panel mounted device. It
operates by 24 V dc supply. PLC and FM 352-5 is
The organization of control system is done like
decentralized control system (DCS) as shown in figure 5.
A DCS distributes device control between a central
process controller and local process controllers. In this
scheme PLC works as central process controller while
FM352-5 works as local process controller. PLC gets
inputs from all other subsystems of IOT and according to
stored program it updates its digital and analog outputs. In
this way it controls the overall system operation. This

amplifier system is able to operate from local as well as
remote panel.
Various operating parameters values of
subsystems are given to PLC system via signal
conditioning units (SCUs). These SCUs provide digital
or/and analog signals compatible with PLC system. These
signals are interfaced with the PLC system via its I/O
modules and ultimately interfaced with CPU via
backplane bus as shown in figure 5.

HMI is used to log commands from local panel
such as select local/remote (L/R) operation,
system off, Reset, B_H on, S_B on, Tx on, RF
on, RF off. It is used to set control grid voltage
in the range -80 to -300 V by default this
voltage is -150 V, whenever this voltage crosses
defined range it generates alarm. It also
indicates all the faults/interlocks.
FM352-5 gets digital i/p signals such as HV
ready, RF on and quiescent current status from
PLC. It gets other digitals i/p signals such as
IOT arc, circulator arc, excess i/p RF drive,
excess RF reflected at o/p from RF SCU. FM
352-5 generates 2 digital o/p in which one is
used to RF on/off for RF switch and other is
used to HV off.
CONTROL SYSTEM OPERATION
Control operation is depicted in flow chart
Figure 5: Employed s7- 300 PLC system in DCS scheme.
Total signals incorporated are as following:
 17 analog input signals are incorporated out of
which 7 signals are 4-20 mA current signals (2
flow rate and 5 temperature monitoring signals).
Other 10 signals are 0-10 V voltage sense
signals out of which 6 signals are voltage and
current sense signals of electron gun auxiliary
supplies. Other 2 signals are voltage and current
sense signals of solenoid power supply.
Remaining 2 signals are sense signals from
beam voltage (from potential divider) and beam
current (from hall sensor and its signal
conditioning unit).
 2, 0-10 V analog output signals are incorporated
among which one is used to generate linear
increasing filament voltage and other is used to
control the control grid supply.
 14 digital i/p channels (0 volts as logic 0 and 24
V as logic 1) are incorporated out of which 5
channels are digital i/p commands from remote
namely system off, reset, B_H on, S_B on and
Tx on. Other 6 channels are used for digital
status signals of auxiliary electron gun supplies.
One i/p is used for series combination of limit
switches from flow signals of LCW water. One
i/p is used for door interlock of HV deck and
remaining one is used for air pressure switch.
 4 digital o/p signals (logic level is same as digital
i/p signals) are incorporated out of which 1
digital o/p is used to initiate the turn on
operation i.e. heater I step on. Other one channel
is used for Tx on and remaining 2 channels are
used to interface with FM 352-5 for fast
interlock processing in which one is HV ready
signal and other is quiescent beam current status
signal.
Figure 6: Flow chart of operation of IOT amplifier
system.
Here all preconditions are necessarily included
monitoring of coolants flow and temperature status. At
any stage of operation cycle whenever any precondition is
not satisfied control system detects the fault, latches it and
takes the amplifier system to a predefined safe stage
according to program of PLC.
RESULTS AND CONCLUSION
It is noteworthy that PLC operates in cyclic
fashion where the one cycle execution time for slow
interlock signal is found to be much less than 100 ms,
while the time critical fast interlock execution time is
found to be less than 10µs. These timing ranges are
meeting the requirement regarding maximum allowed
overload period of the IOT amplifier system. This system
has been tested up to about 50 hrs satisfactorily with nil
false tripping in the environment of indus-2 RF area. It
saved a lot of wiring and maintenance efforts. So it is
found suitable as control, interlock and monitoring system
of 80 kW high power IOT amplifier system.
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REFERENCES
http://www.e2v.com
http://support.automation.siemens.com