Nov’07

DC Power Principles

Why DC Power

DC Power System – Overview

DC Output Current flow

Terminology

Provisioning considerations

DC Power System Principles

Types of Power Systems

DC OUTPUT

DC/DC CONVERTER

AC INPUT

POWER SUPPLY OR RECTIFIER

BATTERY CHARGER

Battery

UPS

INVERTER

~ =DC OUTPUTDC INPUT = =

AC OUTPUTDC INPUT = ~DC

OUTPUT

AC INPUT ~ =

AC OUTPUT

Battery

DCAC INPUT ~ = = ~

Provide reliable DC Power for Telecom Equip.No.

1

2

3

4

5

No.

1

2

3

4

5

Battery

DC OUTPUTAC INPUT ~ =

• Most telecom equipment is designed to operate with DC input voltage.

Why choose DC Power ?

Provide equipment power when AC is absentNo.

1

2

3

4

5

No.

1

2

3

4

5

• When the AC supply (mains) is absent, DC supply must come from a stored energy source.

• Currently, DC batteries are the cheapest and most efficient way to store electrical energy.

Battery

DC OUTPUTAC INPUT ~ =

Why choose DC Power ?

Charge the BatteriesNo.

1

2

3

4

5

No.

1

2

3

4

5

• When the AC supply (mains) is restored, the batteries must be recharged.

• Currently, DC batteries can only be charged by DC Power.

Battery

DC OUTPUTAC INPUT ~ =

Why choose DC Power ?

Filter out noise and protect from surgesNo.

1

2

3

4

5

No.

1

2

3

4

5

• A DC supply will act as a line filter thus shielding the telecom equipment from AC system and phase noise.

• A DC supply can also be configured with Over Voltage Protection to prevent high voltage surges from damaging the telecom equipment

Battery

DC OUTPUTAC INPUT ~ =

Why choose DC Power ?

~~~

Monitor and Control the powerNo.

1

2

3

4

5

No.

1

2

3

4

5

Battery

DC OUTPUTAC INPUT ~ =

• Equipment operators can configure and control what power is being supplied to the various telecom equipment.

• Alarming is also provided to monitor the power system’s operation

Why choose DC Power ?

In summary

The reasons for a DC Power System are :

1. Convert AC power to DC for telecom equipment

2. Provide power when AC is absent.

3. Charge the batteries when mains is restored.

4. Provide filtering and surge protection.

5. Provide monitoring and control of power.

DC Power System Principles

Why DC Power

DC Power System – Overview

DC Output Current flow

Terminology

Provisioning considerations

G

DIESELGENERATOR

AC input

Typically AC Mains between 110 – 480V, however other sources of supply can include generators, UPS etc.

AC input

Typically AC Mains between 110 – 480V, however other sources of supply can include generators, UPS etc.

AC Input

DC Power System - Components

G

OVP

MAINS FUSES

DIESELGENERATOR

Input protection

Can be provided by either; in-line fuses, Over Voltage Protection or other such devices.

Input protection

Can be provided by either; in-line fuses, Over Voltage Protection or other such devices.

AC Input

DC Power System - Components

Rectifier#1

Rectifier #2

Rectifier #n

G

OVP

MAINS FUSES

REDUNDANT RECTIFIER

SYSTEMAC/DC

DIESELGENERATOR

Rectifier #n

Rectifier

A Power supply which converts Alternating Current to Direct Current; typical output below 60V.

Rectifier

A Power supply which converts Alternating Current to Direct Current; typical output below 60V.

AC Input

DC Power System - Components

ALARM ALARM MODULEMODULE

Rectifier#1

Rectifier #2

Rectifier #n

G

OVP

MAINS FUSES

REDUNDANT RECTIFIER

SYSTEMAC/DC

DIESELGENERATOR

Rectifier #n

Monitor & Control Unit (Alarm module)

Monitors the system and generates alarms if an event occurs outside of normal operation.

Monitor & Control Unit (Alarm module)

Monitors the system and generates alarms if an event occurs outside of normal operation.

AC Input

DC Power System - Components

ALARM ALARM MODULEMODULE

Rectifier#1

Rectifier #2

Rectifier #n

G

OVP

MAINS FUSES

BATTERY BANK

REDUNDANT RECTIFIER

SYSTEMAC/DC

DIESELGENERATOR

Rectifier #n

BATTERY BANK

Battery Bank / StringA battery bank is 1 or more battery strings.A battery string is a number of batteries connected in series to provide the required operating voltage

Battery Bank / StringA battery bank is 1 or more battery strings.A battery string is a number of batteries connected in series to provide the required operating voltage

AC Input

DC Power System - Components

ALARM ALARM MODULEMODULE

Rectifier#1

Rectifier #2

Rectifier #n

G

OVP

MAINS FUSES

LVBD

BATTERY BANK

REDUNDANT RECTIFIER

SYSTEMAC/DC

DIESELGENERATOR

Rectifier #n

BATTERY BANK

Low Voltage Battery DisconnectTo prevent deep discharging of the batteries.Operated by the MCU when a user-configured low battery voltage point is reached.

Low Voltage Battery DisconnectTo prevent deep discharging of the batteries.Operated by the MCU when a user-configured low battery voltage point is reached.

AC Input

DC Power System - Components

ALARM ALARM MODULEMODULE

Rectifier#1

Rectifier #2

Rectifier #n

G

OVP

MAINS FUSES

LVBD

BATTERY BANK

REDUNDANT RECTIFIER

SYSTEMAC/DC

DIESELGENERATOR

Rectifier #n

LV

LD

BATTERY BANK

Low Voltage Load DisconnectReduces the drain on the batteries by non-priority loads.Operated by the MCU when a user-configured low battery voltage point is reached.

Low Voltage Load DisconnectReduces the drain on the batteries by non-priority loads.Operated by the MCU when a user-configured low battery voltage point is reached.

AC Input

DC Power System - Components

ALARM ALARM MODULEMODULE

Rectifier#1

Rectifier #2

Rectifier #n

G

OVP

MAINS FUSES

BATTERY DISTRIBUTION

BATTERY BANK

REDUNDANT RECTIFIER

SYSTEMAC/DC

DIESELGENERATOR

Rectifier #n

LV

LD

BATTERY BANK

Distribution

System hardware for distributing the DC power to the load. Hardware can include; battery breakers, MCB or blade fuses.

Distribution

System hardware for distributing the DC power to the load. Hardware can include; battery breakers, MCB or blade fuses.

AC Input

DC Power System - Components

LVBD

NONE PRIORITY

LOAD

LOAD(pc’s or different voltage)

ALARM ALARM MODULEMODULE

Rectifier#1

Rectifier #2

Rectifier #n

G

OVP

MAINS FUSES

BATTERY DISTRIBUTION

BATTERY BANK

DC-DC orDC/AC

REDUNDANT RECTIFIER

SYSTEMAC/DC

DIESELGENERATOR

Rectifier #n

LV

LD

PRIORITYLOAD

BATTERY BANK

Load

Any equipment connected to the distribution of the DC system.

Load

Any equipment connected to the distribution of the DC system.

AC Input

DC Power System - Components

LVBD

Load

Any equipment connected to the output of the DC system.

Load

Any equipment connected to the output of the DC system.

NONE PRIORITY

LOAD

LOAD(pc’s or different voltage)

ALARM ALARM MODULEMODULE

Rectifier#1

Rectifier #2

Rectifier #n

G

OVP

MAINS FUSES

LVBD

BATTERY DISTRIBUTION

BATTERY BANK

DC-DC orDC/AC

REDUNDANT RECTIFIER

SYSTEMAC/DC

DIESELGENERATOR

Rectifier #n

LV

LD

PRIORITYLOAD

BATTERY BANK

BATTERY CHARGER

Battery

DC

OUTPUT

AC INPUT ~=

AC Input

DC Power System - Overview

Why DC Power

DC Power System – Overview

DC Output Current flow

Terminology

Provisioning considerations

DC Power System Principles

Eltek Power System

Battery Bank

DC OUTPUTAC INPUT

DC Power System – Current Flow

AC Input OK

AC Input Outage

AC Input restored• Load supplied by DC Power System

• Voltage is at Float Voltage to maintain the charge on the batteries.

Eltek Power System

Battery Bank

DC OUTPUTAC INPUT

DC Power System – Current Flow

AC Input OK

AC Input Outage

AC Input restored• Load supplied by Battery Bank

• Small amount of current to System for alarm and monitoring devices.

Eltek Power System

Battery Bank

DC OUTPUTAC INPUT

DC Power System – Current Flow

AC Input OK

AC Input Outage

AC Input restored• Load supplied by DC Power System

• Batteies recharged by DC Power System. Initially maximum allowable/available current supplied, then reduces as battery charge level increases.

Why DC Power

DC Power System – Overview

DC Output Current flow

Terminology

Provisioning considerations

DC Power System Principles

•W = I x V

•I = W / V

•V = W / I

Terminology – Power Triangle

Current(I)

Power(W)

Voltage(V)

Terminology – Output Characteristics

Constant Power : if the voltage is varied, the current value will

be conversely adjusted to maintain a constant power output.

Constant Current : If the voltage is varied, the power output

will be corresponding adjusted to maintain a constant current

output.

Constant Voltage: If the current is varied, the power output will

be corresponding adjusted to maintain a constant voltage output.

Terminology - Abbreviations

PR : Power Rack; a shelf where rectifiers are inserted.

MCB : Miniature Circuit Breaker

BB : Battery Breaker

MTBF : Mean Time Before Failure; Calculated value of the

probability of failure rates

Why DC Power

DC Power System – Overview

DC Output Current flow

Terminology

Provisioning considerations

DC Power System Principles

NONE PRIORITY

LOADRectifier

#1

Rectifier #2

Rectifier #n

LVBD

BATTERY BANK

Rectifier #n

PRIORITYLOAD

BATTERY BANK

ALARM ALARM MODULEMODULE

MAINS FUSES

BATTERY DISTRIBUTION

LV

LD

3. No. of Outputs ?

AC Input

Provisioning : 6 Key Questions

1. System Voltage ? (+24/-48/-60/other)

NONE PRIORITY

LOAD

PRIORITYLOAD

2. Max Load ?

BATTERY BANK

BATTERY BANK5. Back-up Time ?

Rectifier#1

Rectifier #2

Rectifier #n

Rectifier #n

Rectifier#1

Rectifier #2

Rectifier #n

Rectifier #n

4. Rectifier Recharge time / Redundancy ?

LVBD

6. End Voltage ?

System in normal operation

Provisioning - Redundancy

100A

Battery Charging

Capacity approx 150A, thus “N + 1”

Load

100A

System has no redundancy

Increased recharge time

Provisioning - Redundancy

Load

100A

Can the batteries charge ?

100A

Capacity approx 120A

?

System has no redundancy and reduced standby time

Provisioning - Redundancy

10A

Load

100A

Discharging the batteries

100A

Capacity approx 90A

Provisioning – Battery Breakers

800AhBattery bank

Capacity approx 150A

Load

100A

LVBD

What is the most suitable rating of the BB ?

Too small and it will trip during normal operation; but too big and you waste money

? Charging :150A – 100A = 50 A max

Discharging:100A load max

Thus 150A will suit, though 125A is possible if nec.

Provisioning – Earthing Types

Clean Earth

CABINET

Exchange Link

CABINET

End of Presentation

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