Ametek RF3 SCR Series Operation and maintenance manual

SCR POWER CONTROLLER
Instruction, Operation and
Maintenance Manual
Number: 9100047
Revision 3
530 Lakeview Plaza Blvd, Ste C
Worthington, Ohio, USA 43085
Toll F re e : 1 - 8 88- PWR- C NTL (7 9 7 -26 85)
Ph o n e: 61 4 -3 0 8-550 0
Fa x : 614 - 3 08 - 5506
Web:
w w w. hd r p ow e r. c o m
RF3 SCR Series
30-1200 Amperes
Three-phase
Phase-fired

This manual applies to all Model RF3 SCR Power Controls. Former RF3 manual – 9100018 has been
replaced with this manual.
For the support representative nearest you, please call Ametek HDR Power Systems main office at (614)-308-
5500.
Revision 1 April 2015 Initial Release
Revision 2 July 2015 Revised Address
Revision 3 Aug 2022 General Revision
 2022 by Ametek HDR Power Systems. No portion of this document may be reproduced either mechanically or electronically without the
prior consent of Ametek HDR Power Systems.

RF3 SCR Power Controller Table of Contents
Rev 3 Ametek HDR Power Systems i
TABLE OF CONTENTS
IMPORTANT SAFETY INSTRUCTIONS ............................................................................................................. 1
CHAPTER 1 - DESCRIPTION .............................................................................................................................. 3
1.1 General Description 3
1.2 Application 3
1.3 Operation 3
1.4 Selecting the Proper Rated Power Controller 4
1.5 Specification 4
1.6 Option LG (Lug Kit) 4
1.7 Additional Options 4
CHAPTER 2 - INSTALLATION ............................................................................................................................ 7
2.1 Mounting the RF3 7
2.2 Input/Output Wiring 7
2.3 Fan Wiring (applicable to models rated 90 A and higher) 7
2.4 Wiring Overtemperature Contacts 8
2.5 Command Signal Input 8
2.6 Determining Line Frequency 9
2.7 Voltage Changeover 9
CHAPTER 3 - OPERATION ............................................................................................................................... 11
3.1 General 11
3.2 Front Panel Indicators 11
3.3 Command Input Control 11
3.4 Remote Manual Control with a Potentiometer 12
3.5 Auto/Manual Control with a Controller and Remote Potentiometer 13
3.6 On/Off Control 14
3.7 Shutdown 14
3.8 Overcurrent Trip 15
CHAPTER 4 - THEORY...................................................................................................................................... 17
4.1 Functional Description 17
4.2 Overview of the RF3 17
4.3 Digital Firing Control Circuit 17
4.4 Pulse-Train Firing 17
4.5 Phase-Lock Loop 17
4.6 SPAN and ZERO Controls 18
4.7 Voltage-Squared Feedback 18
4.8 Shut-down 18
4.9 Soft-Start Circuit 18
CHAPTER 5 – TROUBLESHOOTING ............................................................................................................... 19
5.1 Customer-Service Program 19
5.2 Troubleshooting Typical Symptoms 19
5.3 Static Precautions when Servicing 19
5.4 Environmental Problems 20
5.5 Input Power and Load Connections 20
5.6 Correcting Troubles in the RF3 Itself 21
CHAPTER 6 - SERVICE ..................................................................................................................................... 23
6.1 Communication Procedures 23
6.2 Spare Parts Orders – Routine or Emergency 23
6.3 Spare Parts List 24

Table of Contents RF3 SCR Power Controller
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6.4 Drawing List 25
CHAPTER 7 – WARRANTY POLICY ................................................................................................................ 26
7.1 Warranty 26
7.2 In-house Repair Services 26
APPENDIX .......................................................................................................................................................... 28
Appendix A – System Schematic 28
Appendix B – 30-225 A Outline 29
Appendix C – 350-500 A Outline 30
Appendix D – 650 A Outline 31
Appendix E – 800-1200 A Outline 32

RF3 SCR Power Controller Table of Contents
Rev 3 Ametek HDR Power Systems iii
TABLE OF CONTENTS
Par. Title Page
ILLUSTRATIONS
Figure 2.1 Fan and Thermostat Connections .................................................................................................. 8
Figure 2.2 Isolated/Non-Isolated Switches ...................................................................................................... 9
Figure 2.3 T1, T2 Transformer Connections ................................................................................................... 9
Figure 3.1 Control Panel .................................................................................................................................. 11
Figure 3.2 Process Controller Input Connections ........................................................................................ 12
Figure 3.3 Remote Control with a Potentiometer ......................................................................................... 12
Figure 3.4 Auto/Man Control with Controller and Remote Potentiometer ................................................. 13
Figure 3.5 On/Off Control ................................................................................................................................ 14
Figure 3.6 Shutdown Control .......................................................................................................................... 14
Figure 3.7 Current Limit/Trip Board ............................................................................................................... 15
Figure 4.1 AC Switch and SCR On-time ......................................................................................................... 17
TABLES
Table 1.1 kVA vs. Leakage Impedance ............................................................................................................ 4
Table 1.2 RF3 Model Number Breakdown ....................................................................................................... 4
Table 1.3 General Specifications of RF3 Models ............................................................................................ 5
Table 2.1 Wire Size Information ........................................................................................................................ 7
Table 2.2 Transformer Voltage Wiring ........................................................................................................... 10
Table 5.1 Troubleshooting Chart (Symptoms and Solutions) ..................................................................... 21
Table 5.2 Torque Specifications ..................................................................................................................... 21
Table 6.1 RF3 Spare Parts List ....................................................................................................................... 24
Table 6.2 RF3 Drawing List ............................................................................................................................. 25

Table of Contents RF3 SCR Power Controller
iv Ametek HDR Power Systems Rev 3

RF3 SCR Power Controller Safety Instructions
Rev 3 Ametek HDR Power Systems 1
SAVE THESE INSTRUCTIONS
IMPORTANT SAFETY INSTRUCTIONS
WARNING
Observe all warnings and cautions in this manual. Failure to do so may result in serious injury or death.
Refer all service to properly trained and qualified service personnel. Never work alone.
Lethal voltages exist on exposed heat sinks even if the power controller is turned off. Remove power and lock
out power before attempting any service.
This manual contains important safety instructions that must be followed during the installation and
maintenance of the SCR Power controller. Read this manual thoroughly before attempting to operate this
Power controller.
An appropriate branch circuit fused disconnect or circuit breaker with this Power Controller is required to
ensure the safety of operating personnel.
CAUTION
HAZARDOUS VOLTAGES exist at the Power Controller Heat Sinks and at the Load, AT ALL TIMES, when
input voltage is connected. This condition exists even when the Power Controller is set to deliver zero output.
Printed circuit boards contain sensitive components that can be damaged by electrostatic discharge (ESD).
Observe precautions for handling electrostatic sensitive devices. Reference Maintenance and Troubleshooting
(Chapter 5) of this manual for details
In case of fire, use a dry chemical fire extinguisher to put out the fire. Using a liquid fire extinguisher may
cause electric shock.
The SCR Power Controller makes use of components dangerous for the environment (electronic printed circuit
boards, electronic components). The components removed must be taken to specialized collection and
disposal centers.

Safety Instructions RF3 SCR Power Controller
2 Ametek HDR Power Systems Rev 3

RF3 SCR Power Controller Description
Rev 3 Ametek HDR Power Systems 3
CHAPTER 1 - Description
1.1 General Description
The RF3 is a Three-phase, phase-fired power controller, and can operate with a wide variety of input
signals and line voltages up to 575 Vac and currents ranging from 60 through 1200 amperes. The
RF3’s output voltage is proportional to its input signal. The RF3 features pulse-train firing which
provides high immunity to possible SCR firing disturbances, and phase-lock loop circuitry which
ensures line frequency synchronization. Other features are input isolation from ground, soft-start, and
automatic restart circuitry. Terminals are provided to permit connection of a variety of external control
methods. A more detailed description of the features mentioned above is provided in Chapter 6 of this
manual.
1.2 Application
Phase-Fired SCR Power Controllers provide infinitely variable firing angles for precise control of three-
phase power to resistive or inductive loads. This precise control is essential for transformer coupled
loads or loads with great resistance changes due to temperature or start-up. Phase-Fired units may
also be used on straight resistive loads as well, but the lower power factor and higher harmonics may
present a problem to other equipment mounted nearby. A zero fired model would be a better choice.
1.3 Operation
The RF3 accomplishes power control by the switching action of a pair of inverse-parallel power SCRs.
The switching, or gating, of the SCRs is controlled by a digital firing control circuit synchronized “in
phase” with line frequency (either 50 or 60 Hz). A soft-start (approximately a 12 cycle ramp) feature is
standard that allows the Power Controller to fire into the primary of a transformer or to control power to
heating elements which have a large resistance change during start-up. The output may be adjusted
by the on-board multi-turn potentiometers or by a voltage or current signal from a process controller.
ZERO and SPAN controls allow the user to calibrate the SCR unit's output to the process command
signal. Terminals are available for connection of a remote manual potentiometer.
The Three-Phase Overcurrent Trip is included and provides circuit protection from output current
overloads by serving as a fast-gate shutdown. (similar to an electronic fuse.) Trip point is adjustable
from 30% to 200% of the SCR Power Control’s current transformer rating. When the peak current
level exceeds the preset trip level, SCRs are gated off, and the load current is shut down within 1/2
cycle.
Another feature of the overcurrent trip is an automatic reset. This is included with the current limit and
current regulation. Open the unit and locate the auto reset switch and reset pushbutton. With this
switch in the On position, the unit will continue to reset until the fault clears. If in the Off position, the
unit will remain shut off until the reset PB is operated. The auto reset switch will always be in the off
position unless specified on the order.
The overcurrent trip includes a Form C relay output and provisions for a remote overcurrent reset push
button. The relay output terminals are 39 and 40 for the N.C. and 40 and 41 for the N.O. The remote
reset terminals are 37 and 38. Reference Figure 3.7.

Description RF3 SCR Power Controller
4 Ametek HDR Power Systems Rev 3
1.4 Selecting the Proper Rated Power Controller
Use the Table below to select the proper sized RF3. You will need the incoming line voltage and the
transformer leakage impedance. For voltages other than 480V, ratio the incoming voltage using the
480V chart provided below. For example, a 240V system the kVA would be half that on the chart for
any given kVA. The kVA is based upon the one cycle surge ratings of the SCRs installed in each of
the power controls.
Table 1.1 kVA vs. Impedance
Impedance
4% 6% 8% 10% 12%
Current Rating kVA
60 Amps 18 26 35 44 50
120 Amps 35 53 70 87 100
180 Amps 48 74 100 130 150
225 Amps 65 110 150 190 190
350 Amps 82 123 163 204 246
500 Amps 132 198 265 331 400
800 Amps 240 359 480 600 665
1200 Amps 499 747 998 998 998
1.5 Specification
Specifications for the RF3 SCR power controller are given in Tables 1.1 and 1.2.
Table 1.2 RF3 Model Number Breakdown
RF3 – 480 – 225 – NO – LG – 01
NOTE: N.O. Thermostat is included in current ratings above 60 A.
1.6 Option LG (Lug Kit)
Option LG will provide compression lugs for the 350-1200 A Power Controllers.
1.7 Additional Options
The options described above are the ones most commonly used. Additional options are available. For
more information, contact Ametek HDR Power Systems.
120 Vac - 120
240 Vac - 240
400 Vac - 400
480 Vac - 480
575 Vac -
575
30 A rms - 30
60 A rms - 60
90 A rms - 90
120 A rms - 120
180 A rms - 180
225 A rms - 225
350 A rms - 350
500 A rms - 500
650 A rms - 650
800 A rms - 800
1000 A rms - 1000
1200 A rms
-
1200
N.O. Thermostat - NO
N.C. Thermostat - NC
Extended Ramp - ER
Lug Kit (>225 A) - LG
Can have multiple selections
4-20 mA - 01
0-10 Vdc - 02
0-5 Vdc - 03
Auto/Man - 04
Manual Pot input - 05
Others
-
xx

RF3 SCR Power Controller Description
Rev 3 Ametek HDR Power Systems 5
Table 1.3 General Specifications of RF3 Models
Input line voltage: * 120, 240, 400, 480, or 575 Vac,
+10%, -15% , Three-phase
Line frequency: * 50 or 60 Hz
Current rating:
*
As indicated by model number (refer to Table 1.2)
Thermostat contact rating: 120 Vac, 5 A; resistive
Input Signal:
Non-isolated
Isolated
0 to 1.5 V (min); 0 to 10 V (max)
0 to 6 mA (min); 0 to 20 mA (max)
Control methods: 1. Potentiometer, 5 kΩ, 1/2 watt (Customer-supplied).
2. Dry contact closure (customer-supplied).
3. Temperature or process controller
*
*
Control signal input impedance:
Non-isolated input
Isolated input
1500 Ω
500 Ω
Control signal isolation:
From SCRs 2,500 Vac
From ac power input lines 2,500 Vac
From chassis 500 Vac
Power output:
Voltage regulation Voltage Squared
Power output linearity versus
control signals input
+2% (Non-isolated)
+5% (Isolated)
Power SCRs protection:
Current surge Subcycle I² T semiconductor fuse.
Transient voltage spikes (dv/dt) Metal Oxide Varistor (MOV) and R-C snubber across each SCR pair; all
SCRs have PIV rating of 1,400 V.
Miscellaneous:
Phase-firing timebase 0 º to 180 º conduction per SCR
Controls: ZERO and SPAN potentiometers; 10-turn, screwdriver-adjustable.
Fan
-
cooling power (as applicable):
For 90 A through 225 A units 0.42 amperes, 50 VA (50 Hz)
0.38 amperes, 46 VA (60 Hz)
For 350 A through 500 A units 0.63 amperes, 76 VA (50 Hz)
0.57 amperes, 69 VA (60 Hz)
For 650 A through 1200 A units 4.2 amperes, 504 VA (50 Hz)
3.6 amperes, 432 VA (60 Hz)
Ambient Temperature range:
Environment 32 ºF to 122 ºF ( 0 ºC to 50 ºC) surrounding air
Pollution degree 2, Overvoltage Category III
Storage 14 ºF to 158 ºF ( -10 ºC to 70 ºC)
Weight per unit: Current Rating
30 through 225 A
350, 500 A
650 A
800, 1000, 1200 A
lbs
47
60
126
231
kg
18.2
27.3
57.3
105
Outline and mounting: See appropriate drawing in Appendix
* Specify with order
** If you will be using temperature/process controller, specify its output; e.g., 4-20 mA, 0-10 Vdc, 2-10 Vdc,
etc. with your order.
NOTE: The RF3 should be tested or operated with an adequate load since an open output will have line
voltage at the load connection

Description RF3 SCR Power Controller
6 Ametek HDR Power Systems Rev 3

RF3 SCR Power Controller Installation
Rev 3 Ametek HDR Power Systems 7
CHAPTER 2 - Installation
2.1 Mounting the RF3
Determine the voltage and current ratings from the nameplate of the unit (refer to Table 1.2). Then
determine space and mounting hole requirements by referring to the outline drawing (at the Appendix)
that applies to your model’s current rating. Mount the unit so the line and load connections are at the
top and ensure that upward airflow over the heat sink fins is unrestricted. On high current models,
allow adequate clearance for routing the relatively large diameter input and output lines.
2.2 Input/Output Wiring
Using appropriately sized and insulated conductors for the voltage and current ratings of your model,
make connections as shown in Figure 2.3. (Refer to Table 2.1 for wire size information). Torque
specifications of bolted connections can be found in Table 5.2.
A ground wire is required for proper operation. Use a 10 AWG or larger wire.
NOTICE
Use copper conductors rated 75 ºC minimum for all model current ratings.
The RF3 is phase-rotation insensitive. That is, three-phase input power can be
connected in any sequence to terminals L1, L2, and L3, and will not cause an out-of-
phase condition.
On the “internal” side of the RF3, the wire from L2 should connect to the appropriate tap of transformer
T1 and T2, depending on the line voltage to be used. Check the T1 and T2 connection by opening the
RF3 cover; T1 and T2 terminal voltages are clearly marked. Reference Chapter 2.7.
Table 2.1 Wire Size Information
Model Size Wire/Cable
30 A 8 to 0 AWG
60 A 8 to 0 AWG
90 A 8 to 0 AWG
120 A 8 to 0 AWG
180 A 6 to 250 MCM
225 A 6 to 250 MCM
2.3 Fan Wiring (applicable to models rated 90 A and higher)
RF3 models rated 90 A and higher with cooling fans require 120 Vac power which must be supplied by
the customer. Fan power should be connected to terminals 21 and 22 as shown in Figure 2.1. Refer
to Table 1.3 for fan power requirements by model.
The RF3 terminals available for the 120 Vac fan connections are shown Figure 2.1 and in the
schematic in Appendix A. Optional 220 Vac fans are available.
WARNING
Branch circuit overcurrent protection required is to be provided in
accordance with the national and local codes of the inspecting authority.

Installation RF3 SCR Power Controller
8 Ametek HDR Power Systems Rev 3
2.4 Wiring Overtemperature Contacts
Normally-open (N.O.) heat sink thermostats are standard on all fan-cooled models (rated 90 A and
higher). These thermostats, which close on high heat sink temperature (200 ºF), may be used to
initiate an alarm, shunt trip, or other device for SCR protection. Thermostat connections are on
terminals 23 and 24 as shown in Figure 2.1.
If desired, normally-closed (N.C.) contacts may be substituted for the normally-open (standard). Heat
sink thermostats are optional on units with current ratings lower than 90 amperes and can be ordered
with either N.O. or N.C. contacts.
FAN POWER
120 Vac
(220 Vac
OPTIONAL)
OVER TEMP
N.O. STANDARD
(N.C. OPTIONAL)
21 22 23 24
Figure 2.1 Fan and Thermostat Connections
2.5 Command Signal Input
HDR’s Phase-Fired SCR Power Controllers have the capability of having either an isolated current or
non-isolated voltage Command Signal input. The standard input impedance is 500 ohms for isolated
and 1500 ohms for non-isolated.
All units are equipped with DIP switches, select “isolated” position for a 4-20 mA command signal and
“non-isolated” for a voltage input such as 0-10 V dc. See Figure 2.2.
The isolated input works best with an offset Command Signal such as 4-20 mA; however, it will work
with both offset and zero based Command Signals. Zero based Command Signals may have a small
amount of non-linearity (input to output) at the low end. This should not be a problem on closed loop
systems.
CAUTION
The application of fan power should precede, or coincide with, the turn-on of
the line voltage source that is to be controlled by the disconnect. How this is
accomplished and ensured is up to the customer.

RF3 SCR Power Controller Installation
Rev 3 Ametek HDR Power Systems 9
Current Input Voltage / Manual Pot Input
Figure 2.2 Isolated/Non-Isolated Switches
2.6 Determining Line Frequency
The RF3 is designed to operate on either 50 or 60 Hz. Usually the RF3 is shipped for 60 Hz operation,
unless otherwise ordered. The RF3 can be set for either ac line frequency by selecting 50 Hz or 60 Hz
on SW3 on the control board on the inside front door.
2.7 Voltage Changeover
On occasion, customers may wish to operate a RF3 SCR Power Controller on line voltages other than
what was specified when originally ordered. The RF3 may be changed to accept a wide range of line
voltages (120, 240, 400, 480, 575 Vac), so long as the load current does not exceed the RF3’s current
rating. This is accomplished by performing the procedure described below.
.
Using the system schematic (located in the Appendix) as reference, perform the voltage changeover
procedure as follows.
1. Open the SCR power controller, and locate transformer T1 and T2. The primary side of T1
transformer will contain two wires (one black, the other white and black), the primary side of T2 will
contain two wires (one red the other yellow). Refer to figure 2.3.
T2 T1
Figure 2.3 T1, T2 Transformer Connections
WARNING
Voltage changeover should be performed by qualified personnel only.
Always remove power and properly lock out power to the unit before
attempting any service.
----OPEN ----
12 3 4C1
C2
NON-ISOLATED-C2
SW2
ISOLATED-C1
SW1

Installation RF3 SCR Power Controller
10 Ametek HDR Power Systems Rev 3
2. Unsolder the Black/White wire on T1 from the voltage tap, and resolder it to the tap desired, as
shown in Table 2.2. Unsolder the Yellow wire on T2 from the voltage tap, and resolder it to the tap
desired, as shown in Table below. Route the wires so that they are physically located under the
transformer terminals.
Table 2.2 Transformer Voltage Wiring
Desired Voltage T1 White &
Black Wire to
T2 Yellow
Wire to
120 120 120
208, 220, 240 240 240
380, 400, 415 400 400
480 480 480
575 575 575
3. Close the unit, and apply line power. The unit is now ready for operation on the line voltage
selected. It is a good idea to identify the unit with a label or tag, noting that RF3 has been
modified for line voltage other than what it was specified for. This may prevent accidental use on
an incorrect line voltage in the future.

RF3 SCR Power Controller Operation
Rev 3 Ametek HDR Power Systems 11
CHAPTER 3 - Operation
3.1 General
This Chapter provides information necessary for proper setup and operation of various methods used
to control the RF3.
a. Front Panel indications
b. Command input control
c. Remote manual control with a potentiometer
d. Auto/manual control with a controller and potentiometer
e. On/off control
f. Shutdown
Figure 3.1 Control Panel
3.2 Front Panel Indicators
Control Power Indicator – A Red Light Emitting Diode (LED) located on the front cover of the unit
signals when the control power is present.
Command Signal Indicator - The Command Signal Indicator is a green Light Emitting Diode (LED)
located on the front cover of the unit. The brilliance of this LED will change with a current Command
Signal. The brilliance increases with an increased Command Signal and decreases with a decreased
Command Signal. The LED will not function with a voltage or manual input.
Blown Fuse Indicator - The Blown Fuse Indicators are yellow Light Emitting Diodes (LED) located on
the front cover of the unit. There is one LED for each phase. Switches on each fuse controls the LED.
3.3 Command Input Control
The RF3 is calibrated at the Factory for the specified input type and normally does NOT need
adjustment. However, should a setup be required use the following methods. Refer to chapter 2.5 for
the Command signal input configuration.
a. Set the ZERO and SPAN controls fully CCW (counterclockwise).

Operation RF3 SCR Power Controller
12 Ametek HDR Power Systems Rev 3
b. Connect a voltmeter across terminals X1 and X3 of the RF3. Set the voltmeter range to measure
full input voltage.
c. Close the fused disconnect or circuit breaker to apply power to the RF3. Turn the Process
controller on and set to demand zero power output.
Figure 3.2 Process Controller Input Connections
d. Adjust the ZERO control CW until the output just turns on, then turn the ZERO control CCW just to
the point where the output voltage reading is zero.
e. Set the Process controller to demand 100% output. Observing the voltmeter, adjust SPAN CW
just to the point where the reading is below the maximum output voltage. Then adjust SPAN CW
just to the point where the meter reading is at maximum.
f. Repeat steps 3.3d and 3.3ef as necessary, to ensure proper control adjustments have been made.
g. Turn off the line power to the RF3 and disconnect the test equipment. The RF3 is now ready for
automatic operation.
3.4 Remote Manual Control with a Potentiometer
Some applications only require a manual control input and not a closed loop input from a process
controller. This potentiometer may be located on a remote panel near other controls related to the
process being powered by the RF3. It may be calibrated to correspond to a percentage of rated power
output, process temperature, or some other parameter. The potentiometer may by 500 Ω to 5 kΩ, and
should be rated at 1/2 watt, minimum.
a. With the power to the RF3 turned off, connect the potentiometer as shown in Figure 3.3. The CW
position is the full power output position. Terminal TB1-5 is internally connected to a positive dc
voltage source.
Figure 3.3 Remote Control with a Potentiometer
WARNING - ELECTRIC SHOCK CAN KILL
HAZARDOUS VOLTAGES exist at the output terminals and at the load when
the input voltage is connected. This condition exists even when the Controller is
set to deliver zero output. Always remove power and properly lock out power to
the unit before attempting any service, including the load.

RF3 SCR Power Controller Operation
Rev 3 Ametek HDR Power Systems 13
b. Connect a voltmeter across terminals X1 and X3 of the RF3. Set the voltmeter range to measure
the full output voltage.
c. Set the SPAN control and remote potentiometer fully CCW.
d. Close the fused disconnect or circuit breaker to apply power to the RF3. The unit should be
energized, with no output.
e. Adjust the ZERO control CW until the output just turns on, then turn the ZERO control CCW just to
the point where the output voltage reading is zero.
f. Set the SPAN control and remote potentiometer fully CW. The output should be full-on.
g. Observe the voltmeter and slowly adjust the SPAN control CCW, just to the point where the output
voltage reading is at maximum.
h. If necessary, readjust ZERO with remote potentiometer fully CCW and SPAN control and remote
potentiometer fully CW.
i. Turn off the line power to the RF3 and disconnect the test equipment.
3.5 Auto/Manual Control with a Controller and Remote Potentiometer
On closed loop processes it may be desirable to be able to operate the unit manually. The SCR Power
Controller has this capability designed into it. Connect the Command Signal, a Remote Manual control
and an Auto/Manual switch in the Auto position. By switching to the Manual position, the Remote
Manual control operates and the auto signal is disconnected.
With the power to the RF3 turned off, connect the switch, potentiometer, and controller as shown in
Figure 3.4 and remove jumper from terminal TB1-7 and TB1-8. Install the AUTO/MAN switch in the
same general location as the remote manual potentiometer. Note that the full CW position of the
potentiometer is the full-power-output position.
Figure 3.4 Auto/Man Control with Controller and Remote Potentiometer
Place the AUTO/MAN switch to AUTO and calibrate the system as described in steps 3.3b through
3.3h.

Operation RF3 SCR Power Controller
14 Ametek HDR Power Systems Rev 3
3.6 On/Off Control
Some applications require that a simple ON/OFF type control be used. The unit can be used in these
simple applications. It can be connected for turn on by a contact closure.
With the RF3 configured for non-isolated inputs and the power to the RF3 turned off, connect the
system as shown in figure 3.5. A closed contact will turn on (enable) the RF3.
Figure 3.5 On/Off Control
Calibrate the system by performing the steps in 3.3. Note that zero power demand is accomplished by
opening the contacts with the controller, and maximum power demand is present when the contacts
are closed.
3.7 Shutdown
When it is necessary to shutdown or disable the output, it is a simple matter. Connect a dry contact
closure between terminals 3 and 4 of the firing circuit as shown in Figure 3.6. A closed contact will
disable the RF3 output.
Figure 3.6 Shutdown Control
(Output Disabled By Contact Closure)
WARNING
This method of control is not to be used with isolated inputs!