1.INTRODUCTION2.FEATURES OF POWER SYSTEM3.SMPS4.WORKING PRINCIPLE 5.SPECIFICATION OF SMPS POWER PLANT6.SPECIFICATION FOR MODULE7.FUNCTIONAL DESCRIPTION OF POWER SYSTEM8.AC DISTRIBUTION PANEL9.DC DISTRIBUTION PANEL10.POWER SYSTEM CONTROLLER11.FUNCTIONAL DESCRIPTION OF RECTIFIER12.FUNCTIONAL DESCRITION OF POWER SYSTEM

CONTROLLER

The power system is intended primarily to provide uninterrupted DC power Telecom equipments and current for charging the batteries in the presence of AC Mains.

The system works from commercial AC mains which is rectified and regulated to –48V DC and is fed to the equipment (exchange). The system has provision to connect three sets of VRLA

(a)Multi-rack configuration.

(b) Facility to parallel a maximum of 21 nos. (or 22 nos.) of 100A (5600W) rectifier modules operation from three phases, 400V, 50Hz AC input.

(c) Termination for three sets of VRLA batteries and exchange.

(d) System input : Three phase, 4-wire, 50 Hz supply.

SMPS means Switch Mode Power Supply. This is used for D.C-to-D.C conversion. This works on the principle of switching regulation.

The SMPS system is highly reliable, efficient, noiseless and compact because the switching is done at very high rate in the order of several KHz to MHz.

1. Principle of Switching Regulator

2. Principle of Regulation-

Regulation is achieved by modifying the Duty cycle. Duty cycle depends on onetime of transistor, which in turn depends on the width of the pulse applied to the base of the transistor, which is controlled by ‘Pulse width modulation’ by regulator circuit.

1. Principle of Switching Regulator-

2. Principle of Regulation-For maximum efficiency the duty cycle should be less than 0.5.

Switching regulators are more efficient than conventional regulators as the power loss in the switching element is reduced to minimum as it conducts only for a fraction of a cycle.

Specification of SMPS Power Plant

1) Input Voltage 320 V to 480 VFrequency 45 Hz TO 65 Hz

2) Output Voltagein Float Mode -54.0 ± 0.5 V. adj range -48 V to -56Vin charge mode : -55.2 V ± 0.5V

3) Input power factor >0.95 Lag with 25% to 100% load at nominal input.

Specification For Module(1) Input Voltage:(a) 320V to 480V r m s three phase (Nominal Voltage – 400V).(b) Frequency: 45 Hz. 65 Hz.

(2) Output Voltage:Float mode:Nominal voltage: -54.0 + 0.5V,Adjustment range: -48.0 to –56.0 VCharge mode Voltage: -55.2 + 0.5 V

(3) Rated current: 100 Amps

(4) Efficiency :Greater than 90% at full Load and nominal input.

(5) Protection:(a) Short circuit protection.(b) Input over/under voltage protection.(c) Output over voltage protection.

Functional Description Of Power System

This Power System is of multi rack type and consists of the following:(a) Eight racks – One main, one auxiliary and six extension racks.(b) AC Distribution module in each rack.(c) Rectifier modules (A maximum of three modules in extension rack and two each in main rack and auxiliary rack).(d) DC distribution module in each rack.(e) Metering in each rack.(f) Power system controller in main rack.

AC Distribution Panel:

The AC input to the rack is terminated at the bottom of the rack on screw type terminals. Individual AC circuit breakers are provided for each module.

A small signal transformer is mounted on the PSC panel to provide AC input to power system controller card.

DC Distribution Panel

This panel is mounted at the top of the cabinet. The panel incorporates the following :(1) Input from individual rectifier modules terminated on cabinet.(2) DC shunts to monitor current in various paths.(3) Termination of battery 1, 2 and 3.(4) Termination of equipment positive and negative.(5) Fuses for battery 1, 2 and 3.

Power System Controller:

The Power system controller card consists of an electronic circuit which monitors the state of each rectifier module and display their status. It also controls the operation of the module so as to make it work in auto float or auto charge mode.

The various alarms as per following details are displayed on theFront panel with audible alarm.

(1) Mains out of range: Red(2) Load voltage high (above 57V) : Red(3) Load Voltage low (below 42V) : Red(4) Mains fail: Red(5) System overload: Red

Functional Description of Rectifier

The SMPS 50V-5600W rectifier is a state-of-the-art switch-mode power conversion equipment. The boost converter has the inherent advantage of continuous input current waveform, which relaxes the input filter requirements.

Functional Description of Power System Controller

Power system controller is designed to control the modes of operation of rectifiers, acknowledge and displays the status of rectifiers and system and controls parameters of rectifiers. The controller accepts signal from individual rectifiers through 8-pin telephone jack and controls the operation of each individual rectifiers. The total battery current can be suitably programmed to limit the current supplied from the modules through current programming pin in modules.