Why Dc Power

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  • Batteries are awesome sources of direct current power that can be used in conjunction with generators or easily transported for mobile appliances. It is important to have battery checks done on occasion though when larger stationary batteries are used for purposes such as helping to power a generator. You may enjoy the following site for more information, http://www.affordablebatteryspecialist.ca
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Why Dc Power

  1. 1. Why do we need ELTEK Power Supply? - And why do we need Batteries? ? Why Power & Batteries
  2. 2. <ul><li>PROVIDE A RELIABLE DC-POWER SUPPLY TO TELECOM EQUIPMENT. </li></ul><ul><li>CHARGE THE BATTERIES MONITOR AND CONTROL THE SYSTEM TO ACHIEVE A LONG LIFETIME AND MTBF ( MEANTIME BEFORE FAILURE) OF THE COMPLETE SUPPLY- AND BACK-UP SYSTEM. </li></ul>Why Power & Batteries
  3. 3. Why DC and not AC Power Supply? <ul><li>A filter for all the noise (EMC, surges etc) present on the AC power lines. </li></ul><ul><li>All telecom equipment (PABX, Base Stations, Main Switches) have to operate when the AC supply (mains) is absent. The telecom equipment have to be supplied by stored energy while the AC supply (mains) is absent. Batteries are today the cheapest and most efficient way to store electrical energy, and can only be charged by DC. </li></ul>
  4. 4. Why DC and not AC Power Supply ? <ul><li>A DC Power Supply System converts the AC power to DC Voltage, to charge the batteries and to supply the Telecom equipment (load) when mains is present. </li></ul><ul><li>When the AC supply (mains) fails, the batteries will supply the Telecom equipment (load) until the mains supply returns. The rectifier system will then recharge the batteries. </li></ul><ul><li>The DC power supply will monitor and control the system and provide alarms in case of failure. </li></ul>
  5. 5. TYPICAL POWER PLANT <ul><ul><li>Overview / Components </li></ul></ul><ul><ul><li>Current flow </li></ul></ul><ul><ul><li>Voltage sequence Discharge - Recharge </li></ul></ul>
  6. 6. Overview/Components in a Power System NONE PRIORITY LOAD LOAD (pc’s or different voltage) UPS AC/DC - DC/AC ALARM MODULE Rectifier #1 Rectifier #2 Rectifier #n G OVP MAINS FUSES LVBD BATTERY DISTRIBUTION BATTERY BANK DC-DC or DC/AC REDUNDANT RECTIFIER SYSTEM AC/DC DIESEL GENERATOR Rectifier #n LVLD Battery & Load Distribution PRIORITY LOAD BATTERY BANK
  7. 7. Current Flow in a System <ul><li>MAINS INPUT OK </li></ul><ul><li>LOAD SUPPLIED BY THE RECTIFIER SYSTEM </li></ul><ul><li>BATTERIES ON FLOAT CHARGE. </li></ul>RECTIFIER SYSTEM TELECOM EQUIPMENT BATTERY BANK AC INPUT
  8. 8. Current Flow in a System RECTIFIER SYSTEM TELECOM EQUIPMENT BATTERY BANK AC INPUT <ul><li>MAINS INPUT FAILED (ABSENT) </li></ul><ul><li>LOAD SUPPLIED BY THE BATTERIES </li></ul><ul><li>BATTERIES ARE DISCHARGING </li></ul>
  9. 9. Current Flow in a System RECTIFIER SYSTEM TELECOM EQUIPMENT BATTERY BANK AC INPUT <ul><li>MAINS INPUT OK </li></ul><ul><li>LOAD SUPPLIED BY THE RECTIFIER SYSTEM </li></ul><ul><li>BATTERIES ARE RECHARGING </li></ul>
  10. 10. Voltage Sequence in a DC Power System Float charge Battery discharge Battery recharge Mains failure t U 53.5 43.2 -w/current limitation Disconnect Voltage (43,2 / 24=1,8v) Mains resume Charge Current Limitation Normal charge current
  11. 11. BATTERIES <ul><li>Operating principle of the Recombination Technology </li></ul><ul><li>Open Circuit Voltage in relation to the state of charge of the cell </li></ul><ul><li>Float Voltage versus temperature </li></ul>
  12. 12. Operating principle of the Recombination Technology <ul><li>For conventional lead acid cells water is lost during cycling, due to electrolysis. The result of this is regular battery checks and periodic topping-up operations. </li></ul><ul><li>Sealed, valve regulated lead acid battery design eliminates/reduce these problems through continuous recombination of the oxygen during overcharge. During overcharge the following reactions occur: 1. Oxygen is evolved at the positive plate by the reaction; H 2 O -> 1/2 O 2 + 2H + + 2e - and diffuses through the unfilled pores of the seperator to the surface of the negative plate 2. At the negative plate oxigen combines with Pb and sulphuric acid; Pb + H 2 SO 4 + 1/2 O 2 -> Pb SO 4 + H 2 O 3. The charging process electrochemically regenerates the lead in the negative plate, compl. the cycle; Pb SO 4 + 2H + + 2e - -> Pb + H 2 SO 4 As a result, the recombination process with an efficiency higher than 98% completes and reverses the water oxidation. At the end of the process, teh recombination has replaced the water, the electrolyte and the lead in the negative plates without having modified the state of charge of the plates. </li></ul>
  13. 13. Open Circuit Voltage in relation to state of charge of the cell. State of charge (%) V DC 1.90 Open Circuit Voltage (per cell)l 1.95 2.00 2.05 2.10 2.15 25 50 75 100 0 Charge Voltage Open Circuit Voltage
  14. 14. Float Voltage versus temperature (Example from Exide) END OF SESSION....

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