FAX Power Supplies

Section 1-2
Power Supply AC to DC

In this section of the class we will review the power supply section of the FAX
transmitter. We will start with AC and continue on with DC to the PA modules as well
as DC of the control circuitry.

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 FAX Power Supplies
Power Supply
AC - DC of the
transmitter is
“Brown”
blocks
covered in
this section

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Phase to N(gnd) voltage must Phase rotation does not matter. All power
not exceed 300 VAC which is supplies internal to the FAX are single phase.
max AC for power supplies

If the AC line voltage is 190 – 264 VAC Wye, the

transmitter will be connected as Delta and will not have
There will be a slight phase imbalance
a Neutral Bar

WYE Config
Phase-Neu Volt=ph-phV÷√3

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 FAX Power Supplies

See ECM sheets in manual

Section 1 for circuit breaker and
wire sizing for each model.

AC Mains connections in power blocks

Entry points at the top and above
Delta Strapping Shown

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 FAX Power Supplies
Exciters can be ran off
UPS by plugging into
outlet strip connected to
UPS

UPS Connections Panel Optional for FAX5/10

remove wires 20 & 21 on Standard for FAX20/30/40
both ends. UPS can be
120 or 240 VAC 1-Phase
only

Same connections for FAX30/40 by adding

breakers

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 FAX Power Supplies

UPS Connections on TB2

Wires 20 & 21 must be
removed Completely!
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Power Supply Interface
AC In 1 (PH A/B)
Power Supply 1 PA1 V out
AC IN PA DC Out
AC Mains PS ON/OFF +5V Out
Monitor 1 DC Control Fault Outs PA2 V out
PH A-B
PA3 V out DC Out to
Power Supply 2 PA Modules
AC Low Voltage AC IN PA DC Out PA4 V out
Monitor PS ON/OFF +5V Out 7
44 – 52 VDC
Trip point
DC Control Fault Outs
PA5 V out ≈52 A/supply
190 VAC=2.38 VDC
Power Supply 3 PA6 V out
AC IN PA DC Out
PS ON/OFF +5V Out PA7 V out
DC Control Fault Outs

+5V 1A System Bus +5V out

AC In 2 (PH B/C)
+5V Bus 2A Control +5V Out 5 VDC Out
Power Supply 4
AC Mains AC IN PA DC Out 0.75 Amps/PS
PS ON/OFF +5V Out Blower +5V out
Monitor 2 DC Control Fault Outs
PH B-C 2A Ext +5V out
Active Diode
Gating Restrike
Power Supply 5 AC Mains
PA DC Out Restrike
AC IN Fan Fan DC Voltage
PS ON/OFF +5V Out Bussed Fan
DC Control Fault Outs 15A Temp CTRL
50 VDC @4A
AC In 3 (PH A/C) IPA IPA Volts
Power Supply 6 Shared PA
15A
Bussed IPA
VOLTAGE
AC IN PA DC Out
AC Mains Diodes
Monitor 3
PS ON/OFF +5V Out 50 VDC
DC Control Fault Outs
PH A-C
PS Voltage
Scale &
Fault & Meter
PS Fault
Power Supply 7 Buffers (9) MUX
AC IN PA DC Out Each PS Fault (1-7)
x7 PS Voltages (1-8)
PS ON/OFF +5V Out
PS Faults (1-7) PS Voltage
DC Control Fault Outs Each PS Voltage
PA ON/OFF
Temp Temp Sample (1-7)+ Shared
Sensor Flow Sample Cooling Fault
System Cooling
PS DC Control
Flow Fault Fault
Flow Comparator/ Fan Fault Cooling Sample
x7
Latch Cabinet
Sensor MUX Enable
Temperature
MUX A/B
System Fault OFF
For Air Flow
Fan Fault
Interface System Fault
MUX column addresses (2) For Cooling
4
MUX Row Addresses (4) Demux PS Summary Fault
4
Mux A/B AC Mains Fault
4
Fan Fault Input Mod AC Modulator AC
FAX
1A Exciter
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 FAX Power Supplies

+5 VDC Distribution

+50 VDC Distribution

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•Main supply output DC controlled from the micro to the PS Margin Pin. In
Backup control or Lifesupport, and the transmitter is switched between Class C
and Class A/B modes, the System Interface Power Supply Control circuit sets the
PS CTRL (TP18) voltage that drives the Margin pin on the power supply. This is
≈0.6 VDC for Class C and ≈ 1.1 for Class A/B and corresponds to about a 2 Volt
increase when switching from Class C to Class A/B.
•IPA Voltage is bussed from all supplies via diodes. 15 Amp fuse.
•Must have 2 power supplies installed and operational for transmitter to stay on
air.
•Fans are 48 VDC variable speed. 15 Amp fuse. Some of the first model FAX
transmitters had constant speed fans and a slightly different fan control board.
•Fan control voltage is adjusted based on the temperature sensor U9 (Sheet 7)
on the power supply interface board. (0 – 5 VDC). The fans will ramp up to full
speed under certain fault conditions PA FAULT and Reject load power.

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 FAX Power Supplies
•Airflow monitor – Sensor on PS Interface Board. The latest board now has a switch that
provides the ability to set the fault threshold level (Dipswitch S1). See Schematic Page 6.
•5 volt supply is bussed from the main power supplies on the power supply interface and
distributed throughout the power block. 5 Amp fuses are on the power supply interface
board and are difficult to replace. Voltage output is +5 VDC -10 %, +5 % typically 4.75 VDC.
The summing diode drops this down to ≈4.6 VDC
•5 VDC is distributed between power blocks(FAX20/30/40), if AC is lost to 1 power block the
5 V will be fed to it from the other one in that cabinet.
•There are Low Line Voltage monitors on each phase. These fault when the AC line on the
phase drops below approximately 190 VAC. LED’s can be seen by opening the front door and
looking behind the System Interface Card. There are fuses (1 Amp Glass) on each line and
one on neutral.
•Low AC Line also trips PS Fault on system. This also creates a PS Fault. This will be on System
Interface Board in Power Block but will not show up on Multi-Unit Interface
Board(FAX20/30/40) since it is a power block fault.

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 FAX Power Supplies

AC Low Line Detector – PS Interface

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Control 5
VDC
Fuse (F5)

5 VDC Ext
Out
Fuse (F4)

IPA and Fan Fuses

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 FAX Power Supplies

GatesAir # Littlefuse # Size Description

3980488000 0218001.HXP 1 Amp Slo F1-F3,F6 AC Line fuses and Neutral fuse

3980642000 0297005.LXN 5 Amp 32 VDC F4-F5 5 VDC line

3980762001 0218015.MXP 15 Amp 250 V F9-F10 Fan and IPA fuses

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LED’s Match silkscreen, though not so easy to see here or in unit!

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 Universal input 90 – 300 VAC 50/60Hz
– Single Phase
– 2725 Watt DC output

 High-efficiency ~96 %
Picture of PS here
 Supply has on-board power factor correction(>0.98,
nominal)
 Low AC line harmonics
 Hot pluggable via front of transmitter
 One power supply per PA module for high reliability
 Power Supplies bussed via diodes to run IPA and Fans
 Main DC Output adjustable by FAX Controller from 44 to 52
VDC (PS actually allows voltage range of 42 to 58 VDC)
 Auxiliary +5 VDC Output operates control circuitry – All 5
volt outputs are bussed together and in FAX20/30/40 routed
to each power block via diodes

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Pin# In/Out Name on PS Name on PS Intrf BD Description
P1 IN Line 1 (Hot) Line 1 (Hot) AC Line
P2 IN Line 2 (Neu) Line 2 (Neu) AC line
P3 IN Earth (GND) Earth (GND) AC Gnd
P4 OUT V_OUT (-) (-) OUT 48 VDC for PA's (44 – 58 VDC)
P5 OUT V_OUT (+) (+) OUT 48 VDC for PA's (44 – 58 VDC)
P6 OUT V_OUT (+) (+) OUT 48 VDC for PA's (44 – 58 VDC)
P7 OUT V_OUT (-) (-) OUT 48 VDC for PA's (44 – 58 VDC)
A2 IN RS_485+ RS485+ Sets PS V from Micro Module The three
A3 IN LOGIC_GRD GND Ground faults from
A4 OUT PFW PSx FAULT Power Fail Warning PSx Fault x=which PS power
A5 OUT MOD_PRES MOD_PRESx PS Module is present x=which PS (gnd internal) supplies are
B1 Bi 8V_INT 8V_INT Tied Together on PS Interface tied together
B2 IN RS_485- RS485- Used for test on PS
B5 OUT OTW PSx FAULT Over-Temperature Warning Interface
C4 IN ENABLE PSx ON Turns PS on x=which PS Board A4,B5
C5 IN MARGIN PSx V ADJUST Voltage to adjust DC out of supply (0-3 VDC) and D5, this
D2 IN ON/OFF HOT PLUG Tied to GND on PS Intrf Break first;connect last creates one
D4 OUT 5VA PSx +5V OUTPUT Used for +5V bus (0.75 A max) generic PS
D5 OUT Fault PSx FAULT Rectifier Fault Fault in the
FAX

Pins Used on Power Supply

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Power Supply Faults

•There are three faults from the power supply, they are all open-drain outputs from PS. These faults are tied together
and pulled up to 5 VDC on PS Interface Board.
•Rectifier Fault (Fault) – Indicates an internal fault in the supply
•Power Fail Warning (PFW) – Indicates the DC out is <40 VDC, trips approximately 5 mS prior to the voltage
dropping below the 40 VDC threshold
•Over-Temperature Warning (OTW) – activates approximately 5°C before thermal shutdown of
supply(temperature internal to supply not transmitter)

•The Module Present is a ground internal to the supply, this is inverted and bussed with the PS fault.
•In a 5 kW system where all of the power supply slots are not populated there are switches to disable this alarm on
PS Interface Board
•In a 5 kW system the supplies are distributed across the three phases to maintain balance
•A PS fault on the FAX is displayed as a generic fault. The led’s on the PS itself are a better guide to which fault it is.
Refer to the power supply led’s and the table on the next page.

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AC OK DC OK Service
Condition Fault RED FAULT OTW PFW
GREEN GREEN AMBER
OK ON ON OFF OFF 1 1 1
Thermal Alarm ON ON ON OFF 1 0 1
THERMAL SHUTDOWN ON OFF ON ON 0 0 0
Defective Fan ON OFF OFF OFF 0 1 0
Blown AC Fuse ON OFF OFF ON 0 1 0
No AC <15 mS OFF ON OFF OFF 1 1 0
AC Present but OOL Blinks OFF OFF OFF 1 1 0
AC Not Present OFF OFF OFF OFF 1 1 0
Boost Stage Fail ON OFF OFF ON 0 1 0
OVR Volts Latched Shtdwn ON OFF OFF ON 0 1 0
Over Current ON Blinks OFF OFF 1 1 0
NON-Cat Internal Fail ON ON OFF ON 0 1 1
Standby (remote) ON OFF OFF OFF 1 1 0
Service Request (PMBus Mode) ON ON Blinks OFF 1 1 1
Comm Fault (RS485) ON ON OFF Blinks 1 1 1

All Fault outputs on PS are open drain; 1=logic HI pulled up to +5 VDC on PS

Interface Card in Transmitter (See Sheet 5 of Schematic)

Fault AC OK

Service DC OK

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 FAX Power Supplies
AC line power consumption AC line power consumption
of the transmitter for 3-Phase of the transmitter for 1-Phase
operation: operation:

kVA=E*I*√3 kVA= E * I
1000 1000 Transmitter Efficiency:

kW=E*I*√3*PF kW=E*I*PF Eff %=100 * Pout (kW)

1000 1000 Pin (kW)

PF=0.98 for FAX PF=0.98 for FAX

E=Line Voltage E=Line Voltage
I=Line Current I=Line Current

AC line power consumption of the

transmitter for 3-Phase operation: Transmitter Efficiency:

Eff %=100 * 20000 = 67.9 %

kVA=241*72*1.732 = 30.054 29453
1000

kW=241*72*1.732*0.98 = 29.453
1000

These numbers were taken from original

factory test data for training transmitter.
Line current (72 A)is average of the three
phases measured (62,78,76)

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