Samlex America SEC-4825BRM User Manual

N + 1
DC Power
System

Owner's
Manual

Please read this
manual BEFORE
installing the
unit

SEC-4825BRM

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OWNER'S MANUAL | Index

SECTION 1

Safety Instructions ................................................................. 3

SECTION 2

Layout, Dimensions & Input/Output Connections ................ 5

SECTION 3

Design & Principle of Operation ........................................... 7

SECTION 4

Protections ........................................................................ 19

SECTION 5

Installation ........................................................................ 21

SECTION 6

Operation ........................................................................ 23

SECTION 7

Limiting Electro-Magnetic Interference (EMI) ...................... 25

SECTION 8

Troubleshooting Guide ....................................................... 28

SECTION 9

Speci cations ..................................................................... 31

SECTION 10

Warranty ........................................................................ 33

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SECTION 1 | Safety Instructions

IMPORTANT SAFETY INSTRUCTIONS

SAVE THESE INSTRUCTIONS

This manual contains important Safety and Operating Instructions. Please read
before using this unit .

The following safety symbols will be used in this manual to highlight safety
and information:

Please read these instructions before installing or operating the unit to prevent
personal injury or damage to the unit.

1. DO NOT OPEN TO REDUCE RISK OF FIRE OR ELECTRIC SHOCK. THERE ARE NO USER

2. The unit should be grounded to reduce the risk of electric shock. It comes with

3. It is recommended that you return your power supply to a qualied dealer for any

4. To reduce the risk of electric shock, unplug the power supply from the outlet before

5. To reduce risk of damage to electric plug and cord, pull by plug rather than cord

6. An extension cord should not be used unless absolutely necessary. If an extension

WARNING!

!

Indicates possibility of physical harm to the user in case of non-compliance.

!

CAUTION!

Indicates possibility of damage to the equipment in case of non-compliance.

!

WARNINGS!

SERVICEABLE PARTS INSIDE—REFER TO QUALIFIED SERVICE PERSONNEL.

attached power cord that has a 3 prong, grounded 30A, NEMA L5-30P plug. The
grounding prong of the plug is internally connected to the chassis of the unit. When
the power cord is plugged into the corresponding NEMA L5-30R outlet, the chassis
of the unit is automatically connected to the Earth Ground through the Equipment
Grounding Conductor that is connected to the grounding slot of the outlet. The pow­er cord must be plugged into a corresponding NEMA L5-30R outlet that is properly
installed and grounded in accordance with all local codes and ordinances. Never alter
the power cord that has been provided. If the plug of the cord will not t the outlet,
have a proper outlet installed by a qualied electrician. Improper connection can
result in risk of electric shock.

service or repair. Incorrect assembly may result in electric shock or re.

attempting any maintenance or cleaning. Turning off controls will not reduce this risk.

when disconnecting the unit.

cord is used, make sure that it has 3-prong, grounded male plug (NEMA L5-30P) and

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SECTION 1 | Safety Instructions

3-prong, grounded female receptacle (NEMA L5-30R). The size of the current carrying
conductors should be at least AWG#10 for NEMA L5-30.

7. Place the unit in an area that will allow air to  ow freely around the unit. DO NOT
block or obstruct vent openings on the sides and at the back or install the unit in an
enclosed compartment.

8. Keep the unit away from moisture and water.

9. NEVER OPERATE TWO OR MORE UNITS IN PARALLEL.

10. Precautions when working with batteries.

- Batteries contain very corrosive diluted Sulphuric Acid as electrolyte. Precautions should be
taken to prevent contact with skin, eyes or clothing.

- Batteries generate Hydrogen and Oxygen during charging resulting in evolution of explo­sive gas mixture. Care should be taken to ventilate the battery area and follow the battery
manufacturer’s recommendations.

- NEVER smoke or allow a spark or  ame near the batteries.

- Use caution to reduce the risk of dropping a metal tool on the battery. It could spark or
short circuit the battery or other electrical parts and could cause an explosion.

- Remove metal items like rings, bracelets and watches when working with batteries. The
batteries can produce a short circuit current high enough to weld a ring or the like to metal
and thus cause a severe burn.

- If you need to remove a battery, always remove the Negative Ground Terminal from the
battery  rst. Make sure that all the accessories are off so that you do not cause a spark.

CAUTIONS!

!

1. Please ensure that the battery is connected with correct polarity - Positive of the bat­tery to the “Battery +” terminal and the Negative of the battery to the “Battery -”
terminal. Reversal of polarity will blow external Fuse F1. DAMAGE DUE TO REVERSE

POLARITY IS NOT COVERED UNDER WARRANTY.

2. Protect the unit against AC line input transients. Use Transient Suppressor in line with
the AC input.

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SECTION 2 | Layout, Dimensions &

Fig. 2.1 FRONT VIEW

1

1B

Input/Output Connections

1 2 5 346

F2

F1

48V Battery

12 9 98A8B107A7B 11A

Fig. 2.1 BACK VIEW

11B

Fig. 2.1 Layout and Input/Output Connections

Legend - Fig 2.1

FRONT VIEW

1

AC Power ON/OFF Switch Illuminates RED when ON

2

AC Input Breaker 25A.

3

DC Volt Meter / Ammeter Voltage / current on Load Terminals

4

Voltmeter / Ammeter Selector Switch Switches display on Voltmeter / Ammeter (3)

Green LED for Power Supply Modules (PSM)

5

1 to 5

Red LED for fan failure or over temperature

6

of heat sink on the PSM

BACK VIEW

7A Positive (+) Load Terminal

7B Negative (−) Load Terminal

8A Positive (+) Battery Terminal

8B Negative (−) Negative Terminal

9 Cooling Fan 2 x 48V fans. Run continuously

10 Grounding Lug Connect to Earth Ground / System Ground

11A Attached AC Input Power Cord 3 Conductors - each AWG #12

11B AC Input Power Cord Plug 30A, NEMA L5-30P

12 DB-25, D-Sub Connector For remote signaling (Pin Out - Fig 3.2)

F1 External Battery Side Fuse

F2 External Load Side Fuse

STEADY ON: PSM is operating normally
BLINKING: No output. PSM is not synchronizing
OFF: No output. Defective

STEADY ON: Fan failure or PSM over temperature

TUBULAR HOLE: 5/16” Diameter

SET SCREW: 5/16” X 3/8” Long x 24 TPI

25A, 80V (Not supplied)

- ATO Style, FKS Series by Littelfuse

- Part No. 166.7000.525

48V Load

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SECTION 2 | Layout, Output Connection

& Dimensions

1. Dimensions Overall
(including protrusions)
Wide(W): 482.6 mm / 19.00”

Depth (D) : 407.6 mm / 16.05”

407.6

407.6

Height (H): 87.7 mm / 3.45”

2. Dimensions (Mounting Holes)
Width (W): 466.73 mm / 18.38”

Height (H): 76.2 mm / 3.00”

407.6

407.6

482.6

466.73

76.2

482.6

Fig. 2.2 Dimensions

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7.94

87.7

87.7

SECTION 3 | Design & Principle of Operation

DESCRIPTION

SEC-4825BRM is a Switch Mode Power Supply (SMPS), which converts 120 VAC, 50/60 Hz
to 48VDC Nominal (actually 54.8VDC at no load to 54.2V at 25A). It has additional provi­sion for 48V battery backup with 2A charging in conjunction with external 48V Lead
Acid Battery (not supplied).

FEATURES

• 19”,2U(3.5”)heightRackMountdesign

• AdvancedSwitchModeTechnology

• N+1Redundancy:5x5APowerSupplyModulesoperateinparallelunder

forced current share control

• RemotemonitoringthroughOptoIsolated,OpenCollector/OpenEmitter
output signals

• Reliable,48VDCUninterruptiblePowerSource(DCUPS)inconjunction
with external 48V Lead Acid backup Battery (not supplied)

• Highefciencyandcompact

• Protectedagainstshortcircuit,overload,overvoltageandovertemperature

PRINCIPLE OF OPERATION

The unit consists of 2 Sections - Switch Mode Power Supply (SMPS) Section and Battery
Backup and Charging Section.

The SMPS Section is designed using advanced switch-mode technology and active load
share circuitry for high reliability, high efciency and minimum size and weight. It is
modular in construction consisting of 5 x 5A Power Supply Modules (PSM) that are
connected in parallel and operate under forced current share control to deliver a total
of 25A. Each PSM is a stand-alone, 55V Power Supply, which delivers up to a maximum
of 5A continuous. By equalizing the output currents, uniform thermal stress of the
individual PSMs is ensured which has utmost importance for long-term reliability of elec­tronic components. The operating principle of current share mechanism is to measure
the output current of each PSM and to modify the output voltages of the 5 PSMs until
all the 5 PSMs deliver equal output current. Typically, the output currents of the 5 paral­leled PSMs will be within 10% of each other at full output current. The module with
the highest voltage at switching ON automatically assumes the role of a Master and the
others operate as Slaves. Each PSM is required to be interconnected with one another to
a common “SHARE BUS” through a pair of parallel pins marked “JUMP 1” and jumper
wires (Fig. 3.5).

For proper operation of Current Share Control Circuitry / Master - Slave operation, a mini­mum load current is required to ow through each PSM to produce adequate feed back
signal. This minimum pre-load current is provided by the sum of the currents drawn by
the 2 cooling fans and by an internal static load resistor connected across the load output
terminals. This internal pre-load current* is kept to the minimum to reduce dissipation.

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SECTION 3 | Design & Principle of Operation

* NOTE: It is likely that due to drift in the pre-set values of components, the minimum

internal preload current may not be suf cient to provide adequate feedback signal
strength resulting in shut down of one or more modules when no external load is
present (The associated PSM Status LED will  ash and also, the associated signal for
remote indication will oscillate between High and Low). As soon as external load is
applied to the unit, the feed back signal strength will increase and the PSM(s) that
were shut down will also operate normally.

The output is delivered through an isolating Schottky diode to enable connection of
external 48V battery (not supplied) for un-interrupted DC power output. The external
backup battery is kept charged by “Taper Type of Float Voltage Charging” through a
current limiting series resistor that limits the maximum charging current to 2A when the
battery is completely discharged.

The SMPS Section along with the Battery Backup and Charging Section work as a DC
Uninterruptible Power Source (DC UPS) in conjunction with an external 48V, Lead Acid
backup battery (battery is not supplied). As long as 120VAC input power is available,
the unit will put out 54.8VDC to 54.2VDC at the Load Terminals (7A, 7B - Fig 2.1). At
the same time, charging current of up to a maximum of 2A (when battery is completely
discharged to Standing Voltage of 42.8V) will be fed through the Battery Terminals (8A,
8B - Fig 2.1) to charge the external battery. The voltage at the Battery Terminals (8A, 8B

- Fig 2.1) will always be clamped to the actual voltage of the battery corresponding to its

State of Charge. If AC input power fails, the DC load will be instantaneously transferred
to the external 48V backup battery and the battery will start discharging. When AC
input power is restored, the DC load will once again be transferred instantaneously to
the Power Supply Section and the external backup battery will be recharged and kept in
charged condition all the time at  oat Voltage of 54V to 54.6V (when fully charged). If
battery backup function is not used (external 48V backup battery is not connected), the
unit will work as a normal 48V nominal Power Supply.

N+1 Redundancy

5 Power Supply Modules operating in parallel with equal current sharing provides
redundancy. Chance of failure of all the 5 modules is reduced tremendously. If say one
module fails, the remaining 4 modules will share the load current equally. Such re­dundancy is also called N+1 redundancy i.e. if “N” number of paralleled modules are
required to service a certain load, the unit should have 1 additional module (total “N+1”
modules) to provide redundancy. For example, if the rated load drawn from this unit is
20A, 4x5A modules will be required. Using 1 additional 5A module (total 25A) will have
the capacity to service the full load of 20A even if 1 module fails.

OPERATION OF BATTERY BACK-UP AND CHARGING SECTION

Please refer to the schematic at Fig 3.1 (page 9).
Regulated output voltage of 55VDC from the modules (measured at screw terminals
S5 and S6 (Fig. 3.4) is fed to the Positive and Negative DC bus bars and from there to
the output terminals LOAD (+) and LOAD (−) through the isolating Schottky Diode D1.
Although the output voltage at the module terminals S5 and S6 (Fig.3.4) or at the

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SECTION 3 | Design & Principle of Operation

R

BATTERY

BATTERY

LOAD

+

LOAD

POSITIVE BUS BAR

55V
from
PSM

NEGATIVE BUS BAR

+

R1

D3

R2

D2D1

LEGEND

D1, D2 Schottky Diode, 40CPQ060 by International Rectier
D3 10A, 600V Diode “10A6” for reverse polarity protection
R1, R2 Power Resistor 12 Ohm, 35W
R Static Load Resistor, 1K, 5W

Fig 3.1 Schematic - Battery Backup

common DC bus bar (before the Schottky Diode D1) is tightly regulated at the preset
value of 55VDC, the voltage at the output terminals Load (+) and Load (−) will vary
slightly due to the forward voltage drop “Vf” of the isolating Schottky Diode D1 and
the drop along the DC bus bar and wiring. The voltage at the output terminals LOAD

(+) and LOAD (−) will be as follows:

• Atnoexternalload Approximately54.8VDC

• At25Aload  Approximately54.2VDC

+

When there is a requirement of un-interrupted DC power to the load, an external 48V
battery should be connected at the terminals Battery (+) and Battery (−). When input
AC power is available, the load current is supplied by the Power Supply Section through
Isolating Schottky Diode D1. At the same time, the battery is charged to Float Voltage
Level by “Taper Type of Charging” through 2 x 12 Ohm resistors R1 & R2 in parallel with
an effective series resistance of 6 Ohm. This effective series resistance of 6 Ohm will limit
the maximum charging current to 2A. The charging current will be determined by the
following equation (Battery’s internal impedance and battery cable resistance have been
disregarded as their values are negligible as compared to the 6 Ohm effective series
resistance):

Charging Current = (Load Terminal Voltage – Battery’s Intrinsic

Maximum Charging Current (At completely
discharged voltage of 42.8V)

Charging current when fully charged to maxi­mum Float Voltage of 54.6V

State of Charge Voltage) ÷ 6 Ohm

= (54.8V – 42.8V) ÷ 6 Ohm = 2A

25 mA (0.1% of Ah capacity of the battery to
compensate for self-discharge. Battery with
25Ah capacity has been considered)

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SECTION 3 | Design & Principle of Operation

From the above equation, it will be seen that the battery will be charged at a maximum
charging current of around 2A when the battery is completely discharged to Stand­ing Voltage of 42.8V and the charging current will taper to a very low value of around
25mA when the battery is charged to Float Voltage Level of 54.6V.

If input A.C. power is interrupted, the external battery feeds the load instantaneously
through the Schottky Diode D2 (D2 will be forward biased and will by-pass resistors R1
& R2). Voltage available to the load will be approximately 0.2V lower than the battery
voltage due to forward voltage drop across D2. Availability of AC power is signaled for
remote monitoring through opto-isolated signal through D-Sub Connector (Pins 2 and
16 of D-Sub Connector, Fig 3.2. Also see below under “Remote Monitoring of Opera­tional Status”). This signal may also be used to indicate that the load is being powered
by battery (In case external battery is used for battery back-up). When AC input power
returns, load current will be supplied by the Power Supply Section, Diode D2 will be re­verse biased and the discharged battery will be taper charged through 6 Ohm effective
resistance of R1& R2.

* NOTE: The value of charge limiting resistors R1 and R2 is based on a typical 48V,

25Ah deep cycle marine battery. If a different type of battery is used, the value of
the resistor should be adjusted to meet associated charging requirements.

REMOTE MONITORING OF OPERATIONAL STATUS

A provision has been made for remote monitoring of the following operational
conditions and parameters:

a) Operational status of the 5 Power Supply Modules (PSM)

b) Failure condition of the cooling fan(s)

c) Availability of AC input power (Through 120VAC to 5VAC transformer)

d) Output voltage measurement (Across Load Terminals)

e) Output current measurement (Voltage across an internal shunt with Shunt Ratio of

25 mV / 50A or 0.5 mV per Amp)

Signals for remote monitoring of operating conditions at Srls (a), (b) and (c) above are
transmitted to the remote receiving device through open Collector and open Emitter
pins of phototransistor of internal Opto-Isolator (Figs 3.2 & 3.3A).

Outputs for voltage and current measurements at Serials (d) and (e) above are direct
analogue voltages.

The Pin Out of the 25 Pin D-Sub Connector (12, Fig 2.1) providing the above signals for
user interface is given at Fig 3.2.

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SECTION 3 | Design & Principle of Operation

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

21

22

23

24

25

Item Pin No.

1

2

3

4

5

6

7

8

9

2

16

12
19

7

20

8

21

9

22

10
23

11
24

25
13

18

6

Color Code

of Wire

Black

White

Orange

Green

Gray

Violet

Violet

Blue

Blue

Greeb

Green

Yellow

Yellow

Orange

Red

Black

Gray
Blue

Output Pins of

Opto Isolator

Collector

Emitter

Collector

Emitter

Collector

Emitter

Collector

Emitter

Collector

Emitter

Collector

Emitter

Collector

Emitter

- Voltmeter +

- *Ammeter +

Notes:

† For operational conditions at Items 1 to 7, the Transistor Switch inside the

Opto Isolator is in “Saturation” condition (near short circuit between
Collector and Emitter terminals)

* Shunt Ratio 25mV/50A or 0.5mV/Amp.

Fig. 3.2 Pin Out of 25 Pin D-Sub Connector (12, Fig 2.1) for Remote Monitoring

†Operational

Condition or

Parameter (High)

AC input is
available

Fan failure

PSM 1 Normal

PSM 2 Normal

PSM 3 Normal

PSM 5 Normal

PSM 5 Normal

Voltmeter -

*Ammeter -

OPTO-ISOLATED TRANSFER OF SIGNALS FOR REMOTE MONITORING

In this power supply, signals for remote indication of operating conditions at Serials (a),
(b) and (c) on page 10 are transmitted to the remote receiving device through open
Collector and open Emitter pins of NPN phototransistor of internal Opto-Isolator (Fig 3.2
above and Fig 3.3A on page 12). The NPN phototransistor can provide a maximum of
50 mA with a Collector to Emitter voltage of up to 35V. Use of opto-isolated signal
transfer ensures the following at the receiving location:

• Isolatesnoise,groundloops,and/orhighvoltagesfromthepowersupply
from being fed to the external remote monitoring device.

• The+Vccvoltagethatisconnectedtothepull-upresistor(s)/alarmsandrelaysfor

generating alarm signals at the receiving monitoring device (Figs 3.3 B to D, page 12)
comes from an external voltage source and hence, maximum isolation is provided

• AbilitytogenerateTTLlogicsignalswithVccof3.3V/5V(Fig3.3Bfor5VVcc)

• Driverelays/LEDswithVcc of up to 35VDC (e.g. 5V / 12V / 24V) and drive current of

up to 50 mA (Figs 3.3C and 3.3D)

• Abilitytocombinethesignals(OR’d)toformasinglesignalsharingcommon
Logic Ground

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SAMLEX AMERICA INC. | 11