Ametek ZF2 SCR Series Operation and maintenance manual

SCR POWER CONTROLLER
Instruction, Operation and
Maintenance Manual
Number: 9100040
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 rpow e r. c o m
ZF2/ZF3 SCR Series
60-1200 Amperes
Two/Three-phase
Zero-fired

This manual applies to all Model ZF2/ZF3 SCR Power Controls. Former ZF2/ZF3 manual – 9100029 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 September 2014 Initial Release
Revision 2 July 2015 Revised Address
Revision 3 August 2022 General Revision
 2015 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.

ZF2/ZF3 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 Specification 3
CHAPTER 2 - OPTIONS ...................................................................................................................................... 6
2.1 Option UB (Unbalance Alarm) 6
2.2 Option SF (Shorted SCR Failure Alarm) 6
2.3 Option LG (Lug Kit) 6
2.4 Additional Options 6
CHAPTER 3 - INSTALLATION ............................................................................................................................ 7
3.1 Mounting the ZF2/ZF3 7
3.2 Input/Output Wiring 7
3.3 Fan Wiring (applicable to models rated 90 A and higher) 7
3.4 Wiring Overtemperature Contacts 8
3.5 Command Signal Input 8
3.6 Determining Line Frequency 9
3.7 Voltage Changeover 9
3.8 Options 10
CHAPTER 4 - OPERATION ............................................................................................................................... 11
4.1 General 11
4.2 Front Panel Indicators 11
4.3 Command Input Control 11
4.4 Remote Manual Control with a Potentiometer 12
4.5 Auto/Manual Control with a Controller and Remote Potentiometer 13
4.6 On/Off Control 14
4.7 Shutdown 14
4.8 Unbalance Alarm 15
4.9 Shorted SCR Alarm 16
CHAPTER 5 – OPTIONS SETUP ...................................................................................................................... 19
5.1 Option UB (Unbalance Alarm) 19
CHAPTER 6 - THEORY...................................................................................................................................... 21
6.1 Functional Description 21
6.2 Digital Firing Control Circuit 21
6.3 Variable-Time Base 21
6.4 Pulse-Train Firing 22
6.5 Phase-Lock Loop 22
6.6 SPAN and ZERO Controls 22
6.7 Voltage-Squared Feedback 22
6.8 Shut-down 22
CHAPTER 7 – TROUBLESHOOTING ............................................................................................................... 23
7.1 Customer-Service Program 23
7.2 Troubleshooting Typical Symptoms 23
7.3 Static Precautions when Servicing 23
7.4 Environmental Problems 24

Table of Contents ZF2/ZF3 SCR Power Controller
ii Ametek HDR Power Systems Rev 3
7.5 Input Power and Load Connections 24
7.6 Correcting Troubles in the ZF2/ZF3 Itself 25
CHAPTER 8 - SERVICE ..................................................................................................................................... 27
8.1 Communication Procedures 27
8.2 Spare Parts Orders – Routine or Emergency 27
8.3 Spare Parts List 28
8.4 Drawing List 31
CHAPTER 9 – WARRANTY POLICY ................................................................................................................ 32
9.1 Warranty 32
9.2 In-house Repair Services 32
APPENDIX .......................................................................................................................................................... 34
Appendix A – ZF2 System Schematic 34
Appendix B – ZF3 System Schematic 35
Appendix C – ZF2 60-225 A Outline 36
Appendix D – ZF2 350-500 A Outline 37
Appendix E – ZF2 650 A Outline 38
Appendix F – ZF2 800-1200 A Outline 39
Appendix G – ZF3 60-225 A Outline 40
Appendix H – ZF3 350-500 A Outline 41
Appendix I – ZF3 650 A Outline 42
Appendix J – ZF3 800-1200 A Outline 43
Appendix K – Declaration of Conformity 44

ZF2/ZF3 SCR Power Controller Table of Contents
Rev 3 Ametek HDR Power Systems iii
TABLE OF CONTENTS
Par. Title Page
ILLUSTRATIONS
Figure 3.1 Fan and Thermostat Connections .................................................................................................. 8
Figure 3.2 Isolated/Non-Isolated Switches ...................................................................................................... 9
Figure 3.3 T1 Transformer Connections .......................................................................................................... 9
Figure 3.4 Typical ZF2/ZF3 Line and Load Connections ............................................................................. 10
Figure 4.1 Control Panel .................................................................................................................................. 11
Figure 4.2 Process Controller Input Connections ........................................................................................ 12
Figure 4.3 Remote Control with a Potentiometer ......................................................................................... 13
Figure 4.4 Auto/Man Control with Controller and Remote Potentiometer ................................................. 13
Figure 4.5 On/Off Control ................................................................................................................................ 14
Figure 4.6 Shutdown Control .......................................................................................................................... 14
Figure 4.7 Unbalance Alarm Board ................................................................................................................ 16
Figure 4.8 Shorted SCR Alarm Board ............................................................................................................ 16
Figure 4.9 Unbalance Block Diagram ............................................................................................................. 17
Figure 6.1 AC Switch ....................................................................................................................................... 21
TABLES
Table 1.1 ZF2 and ZF3 Model Number Breakdown ......................................................................................... 3
Table 1.2 General Specifications of ZF2/ZF3 Models ..................................................................................... 4
Table 3.1 Wire Size Information ........................................................................................................................ 7
Table 3.2 Transformer Voltage Wiring ........................................................................................................... 10
Table 5.1 Unbalance DIP Switch Settings...................................................................................................... 19
Table 6.1 Variable-Time-Base Relationship (Example) ................................................................................ 21
Table 7.1 Troubleshooting Chart (Symptoms and Solutions) ..................................................................... 25
Table 7.2 Torque Specifications ..................................................................................................................... 25
Table 8.1 ZF2 Spare Parts List ........................................................................................................................ 28
Table 8.2 ZF3 Spare Parts List ........................................................................................................................ 29
Table 8.3 ZF2/ZF3 Drawing List ...................................................................................................................... 31

Table of Contents ZF2/ZF3 SCR Power Controller
iv Ametek HDR Power Systems Rev 3

ZF2/ZF3 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 7) 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.
E151547
100kA SCCR
IEC 947-5-1

Safety Instructions ZF2/ZF3 SCR Power Controller
2 Ametek HDR Power Systems Rev 3

ZF2/ZF3 SCR Power Controller Description
Rev 3 Ametek HDR Power Systems 3
CHAPTER 1 - Description
1.1 General Description
The ZF2 is three-phase 2-leg/4 zero-fired SCR control and the ZF3 is a three-phase, 3-leg/6 zero-fired
SCR Power Controller. Each of these 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 ZF2/ZF3’s output
voltage is proportional to its input signal. HDR’s zero-fired SCR Power Controls utilize a variable-time-
base that helps maintain constant power to the load. This variable-time-base also helps minimize
temperature overshoot, temperature fluctuations and helps extend the load element’s life due to
reduced thermal shock. The ZF2/ZF3 also 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.
1.2 Application
Zero-Fired SCR Power Controls provide control of three-phase power by the switching action of two
SCRs connected back to back in each controlled phase. By switching at the zero crossing point, RFI
(Radio Frequency Interference) is virtually eliminated. Zero-Fired controllers are versatile enough to
be used in place of mechanical contactors and mercury relays on dryers, kilns, ovens, environmental
chambers, extruders, and most other applications where resistive heating elements are used. Normal
Zero-Fired SCR Power Controllers should never be used on inductive loads.
1.3 Operation
The ZF2/ZF3 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). 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.
1.4 Specification
Specifications for the ZF2/ZF3 SCR power controller are given in Tables 1.1 and 1.2.
Table 1.1 ZF2 and ZF3 Model Number Breakdown
ZF2 (or ZF3) – 480 – 225 – CR – UB – 01
NOTE: N.O. Thermostat is included in current ratings above 60 A.
120 Vac - 120
240 Vac - 240
400 Vac - 400
480 Vac - 480
575 Vac -
575
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
Unbalance Alarm - UB
Shorted SCR Alarm - SF
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

Description ZF2/ZF3 SCR Power Controller
4 Ametek HDR Power Systems Rev 3
Table 1.2 General Specifications of ZF2/ZF3 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 1.1)
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:
Power output linearity versus
control signals input
+3%
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.
Three-phase voltage
imbalance
5% maximum from leg to leg
SCCR Rating 100kA
Miscellaneous:
Zero-firing timebase Variable see 6.3
Controls: ZERO and SPAN potentiometers; 10-turn, screwdriver-adjustable.
Approvals UL/cUL (E151547), CE
Fan
-
cooling power (as applicable):
ZF2
ZF3
For 90 A through 225 A units 0.21 amperes, 50 VA (50 Hz)
0.19 amperes, 46 VA (60 Hz)
0.42 amperes, 50 VA (50 Hz)
0.38 amperes, 46 VA (60 Hz)
For 350 A through 500 A units 0.42 amperes, 76 VA (50 Hz)
0.46 amperes, 69 VA (60 Hz)
0.63 amperes, 76 VA (50 Hz)
0.57 amperes, 69 VA (60 Hz)
For 650 A through 1200 A units 2.8 amperes, 504 VA (50 Hz)
2.4 amperes, 432 VA (60 Hz)
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
ZF2
ZF3
60 through 225 A
350, 500 A
650 A
800, 1000, 1200 A
31 lbs
41 lbs
87 lbs
180 lbs
14.1 kg
18.6kg
39.6 kg
47.6 kg
40 lbs
60 lbs
126 lbs
231 lbs
18.2 kg
27.3kg
57.3 kg
104.8 kg
Outline and mounting: See appropriate drawing in Appendix
* Specify with order

ZF2/ZF3 SCR Power Controller Description
Rev 3 Ametek HDR Power Systems 5
** 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 ZF2/ZF3 should be tested or operated with an adequate load since an open output will have line
voltage at the load connections.

Options ZF2/ZF3 SCR Power Controller
6 Ametek HDR Power Systems Rev 3
CHAPTER 2 - Options
2.1 Option UB (Unbalance Alarm)
This option provides a Form C relay output for monitoring the balance of the 3 phase currents. This
options require current transformers (CTs). If the load currents become unbalanced by more than the
preset percentage, a Form C relay is actuated. Diagnostic indicators are also provided to indicate
operating conditions.
The load unbalance required to trigger an alarm is switch selectable and may be quickly reconfigured
in the field. Typical usage requires no field calibration, although precision trimming adjustments are
included to enhance the circuit’s sensitivity if small current unbalances are to be detected under
controlled conditions. Five light emitting diodes (LEDs) are provided to give a visual indication of the
board’s operation.
On models rated from 60 through 225 amperes the CTs are mounted in the controller and on models
rated from 350 amperes and higher, the CTs are shipped separately.
2.2 Option SF (Shorted SCR Failure Alarm)
This optional circuit monitors each SCR pair’s voltage drop and detects when an SCR is shorted.
Three green LEDs are lit when the SCRs are not shorted. If an SCR shorts, the respective green LED
will go out and the red alarm LED will light and the Form C relay will energize. Relay output and
terminals for connection are provided.
If the Unbalance alarm is provided Shorted SCR Alarm is a “piggy-back” board that mounts on the
Unbalance Alarm.
2.3 Option LG (Lug Kit)
Option LG will provide compression lugs for the 350-1200 A Power Controllers.
2.4 Additional Options
The options described above are the ones most commonly used. Additional options are available. For
more information, contact Ametek HDR Power Systems.

ZF2/ZF3 SCR Power Controller Installation
Rev 3 Ametek HDR Power Systems 7
CHAPTER 3 - Installation
3.1 Mounting the ZF2/ZF3
Determine the voltage and current ratings from the nameplate of the unit (refer to Table 1.1). 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.
3.2 Input/Output Wiring
Using appropriately sized and insulated conductors for the voltage and current ratings of your model,
make connections as shown in Figure 3.4. (Refer to Table 3.1 for wire size information). Torque
specifications of bolted connections can be found in Table 7.2.
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 ZF2/ZF3 is not phase-rotation sensitive. 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.
The fuses included are NOT meant for over current protection, separate branch circuit protection is
required.
On the “internal” side of the ZF2/ZF3, the wire from L2 should connect to the appropriate tap of
transformer T1, depending on the line voltage to be used. Check the T1 connection by opening the
ZF2/ZF3 cover; T1 terminal voltages are clearly marked. Reference Chapter 3.7.
Table 3.1 Wire Size Information
Model Size Wire/Cable
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
3.3 Fan Wiring (applicable to models rated 90 A and higher)
ZF2/ZF3 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
3.1. Refer to Table 1.2 for fan power requirements by model.
The ZF2/ZF3 terminals available for the 120 Vac fan connections are shown Figure 3.1 and in the
schematic at the rear of this manual. 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 ZF2/ZF3 SCR Power Controller
8 Ametek HDR Power Systems Rev 3
3.4 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 3.1.
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 3.1 Fan and Thermostat Connections
3.5 Command Signal Input
HDR’s Zero-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 Vdc. See Figure 3.2.
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.

ZF2/ZF3 SCR Power Controller Installation
Rev 3 Ametek HDR Power Systems 9
----OPEN ----
1
2
3
4
C2
C1
NON-ISOLATED-C2
ISOLATED-C1
----OPEN ----
1
2
3
4
C2
C1
NON-ISOLATED-C2
ISOLATED-C1
Current Input Voltage / Manual Pot Input
Figure 3.2 Isolated/Non-Isolated Switches
(switches may be in different locations on the PC board)
3.6 Determining Line Frequency
The PF2/PF3 is designed to operate on either 50 or 60 Hz. Usually the PF2/PF3 is shipped for 60 Hz
operation, unless otherwise ordered. The PF2/PF3 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.
3.7 Voltage Changeover
On occasion, customers may wish to operate a ZF2/ZF3 SCR Power Controller on line voltages other
than what was specified when originally ordered. The ZF2/ZF3 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
ZF2/ZF3’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. The primary side of T1 transformer
will contain two wires (one black, the other white and black). Refer to Figure 3.3.
Figure 3.3 T1 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.

Installation ZF2/ZF3 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 3.2. Route the wires so that they are physically located under the transformer
terminals.
Table 3.2 Transformer Voltage Wiring
Desired Voltage T1 White &
Black Wire to
120 120
208 240
220 240
240 240
380 400
400 400
415 400
480 480
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 ZF2/ZF3 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.
3.8 Options
UB Option, if ordered by the customer, has been installed and set up at the factory. However, if the
current transformers (CTs) are shipped loose, they should be placed on the load lines when the load
lines are connected (first step in Chapter 3.2), and wired as indicated on the schematic (located in
Appendix A).
Phase 1 CT connects to terminals 51 and 52; Phase 2 CT connects to terminals 53 and 54, and Phase
3 CT connects to terminals 55 and 56.
L3
L2
L1
X3
AC
INPUT
LINE X2
X1
LOAD
GROUND
CONTROL
Note: Unit shown with optional CT’s
Figure 3.4 Typical ZF2/ZF3 Line and Load Connections

ZF2/ZF3 SCR Power Controller Operation
Rev 3 Ametek HDR Power Systems 11
CHAPTER 4 - Operation
4.1 General
This Chapter provides information necessary for proper setup and operation of various methods used
to control the ZF2/ZF3.
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 4.1 Control Panel
4.2 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.
4.3 Command Input Control
The ZF2/ZF3 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 3.5 for
the Command signal input configuration.

Operation ZF2/ZF3 SCR Power Controller
12 Ametek HDR Power Systems Rev 3
a. Set the ZERO and SPAN controls fully CCW (counterclockwise).
b. Connect a voltmeter across terminals X1 and X3 of the ZF2/ZF3. Set the voltmeter range to
measure full input voltage.
c. Close the fused disconnect or circuit breaker to apply power to the ZF2/ZF3. Turn the Process
controller on and set to demand zero power output.
Figure 4.2 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.
Note: The output voltage measurement on Zero Fired Power Controllers with a digital voltmeter
will be erratic except at full output. This is due to the variable pulses to regulate the output.
f. Repeat steps 4.3d and 4.3e as necessary, to ensure proper control adjustments have been made.
g. Turn off the line power to the ZF2/ZF3 and disconnect the test equipment. The ZF2/ZF3 is now
ready for automatic operation.
4.4 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 ZF2/ZF3. 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 ZF2/ZF3 turned off, connect the potentiometer as shown in Figure 4.3. The
CW position is the full power output position. Terminal TB1-5 is internally connected to a positive
dc voltage source.
b. Connect a voltmeter across terminals X1 and X3 of the ZF2/ZF3. 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 ZF2/ZF3. The unit should be
energized, with no output.
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.

ZF2/ZF3 SCR Power Controller Operation
Rev 3 Ametek HDR Power Systems 13
Figure 4.3 Remote Control with a Potentiometer
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 ZF2/ZF3 and disconnect the test equipment.
4.5 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 PF1 turned off, connect the switch, potentiometer, and controller as shown in
Figure 4.4 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 4.4 Auto/Man Control with Controller and Remote Potentiometer

Operation ZF2/ZF3 SCR Power Controller
14 Ametek HDR Power Systems Rev 3
Place the AUTO/MAN switch to AUTO and calibrate the system as described in steps 4.3b through
4.3h.
4.6 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 ZF2/ZF3 configured for non-isolated inputs and the power to the ZF2/ZF3 turned off, connect
the system as shown in figure 4.5. A closed contact will turn on (enable) the ZF2/ZF3.
Figure 4.5 On/Off Control
Calibrate the system by performing the steps in 4.3. 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.
4.7 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 4.6. A closed contact will
disable the ZF2/ZF3 output.
Figure 4.6 Shutdown Control
(Output Disabled By Contact Closure)
WARNING
This method of control is not to be used with isolated inputs!