CHAPTER 1

INTRODUCTION

Telecom power systems secure telecommunication services in case of grid power interruptions

and fluctuations. Delta’s power systems are designed for wireless broadband access and fixed-

line applications, as well as for Internet backbone and data centers. We provide a broad range

of power systems and global services to telecom operators, network manufacturers and

integrators. The essential parts of a system are rectifiers, batteries and a power system

controller. In direct current (DC) power systems, a rectifier converts alternating current (AC) to

DC and provides the power necessary to charge batteries. In AC power systems, an inverter

converts DC into uninterruptible AC. A power system controller monitors and controls the

entire system and site power infrastructure, maximizes battery life, supports energy and cost

savings, and informs the operator of maintenance needs. The power system can be expanded

with renewable energy sources, which creates major energy and operating cost savings. In

regions with highly unstable AC mains conditions, additional AC line conditioning elements

can be integrated into the system for optimal operation. Delta’s InD, OutD and HelpD series

are designed to complement each other. InD stands for indoor power systems, while OutD

solutions are designed for demanding outdoor use. HelpD is our global service concept. Our

CellD and CabD series are designed to fulfil all your power requirements

1.1Rectifier: A rectifier converts alternating current (AC) to direct current (DC) and

provides the power necessary to charge batteries. With a focus on continuously improving the

total cost of ownership, Delta’s rectifiers, combined with advanced control and monitoring

features, help reduce both capital and operational expenditure. Our rectifiers boast an industry-

leading power density while fulfilling space and weight requirements. They leave plenty of

room for other equipment and create savings in packaging and transportation costs. In addition,

their high efficiency lowers total energy consumption and reduces the environmental footprint.

Delta’s rectifiers are easy to install, as their connectors are located at the rear and are hot-

pluggable. Fan cooling with speed control renders operating almost silent. In general the

rectifiers include a wide AC input voltage range, protection against AC overvoltage and

optional protection against loss of neutral, which make this solution very reliable even in the

regions with AC utility network problems.

Fig.1.1: DPR 2700W and DPR 4000W

1.2 Control and Monitoring: ORION controller is the solution for any system, from small to very large, thanks to easy expandability with CAN bus communication and a range of front-end modules. Enhanced functions, such as efficiency mode and genset fuel saving, enable operating cost reductions. Battery management with capacity test and life time prediction and enhanced rectifier functions including redundancy supervision make it easy to monitor system availability and plan site visits in cost effective manner. Remote monitoring and alarming, and consequent cost savings, are ensured with potential-free relay contacts and modem or LAN/Ethernet, SMS, SNMP or Modbus. An integrated web server offers a user-friendly interface with a standard browser both for local and remote communication.

Fig1.2: Orion Controller

CSU502 Suitable for Delta’s CellD shelf and OutD outdoor systems. A USB port provides a user-

friendly interface for local communications together with Delta’s RMS software. Monitoring system

availability is made easy by advanced battery management including a capacity test feature and flexible

supervision of system components.

Fig1.3: CSU 502 Controller

Delta’s InD systems are either DC or AC power systems. Our InD systems fall into three

categories according to size. The flexible CellD and CabD standard platforms meet most needs.

However, should you need a custom solution with a unique architecture, we will come up with

one – to your exact specifications. InD power systems are installed in indoor environments or

in shelters. OutD systems are based on CellD shelf power solutions.

Fig 1.4: InD System

CellD systems are small, just like cells. They can be embedded in the telecom infrastructure

and are often used in OutD outdoor solutions. The products in this series are light and designed

especially for installations with limited space. The CellD platforms are based on two concepts.

One is the complete power system embedded in a single rack, and the other consists of two

racks: a standard rectifier shelf and a distribution unit. The smallest platforms are single-rack

units. The power range of the CellD series is typically from a few watts up to 10 kW in DC

systems. In AC systems, the power range is typically up to 3 kVA.

MidD systems are medium-range power systems that are easy to transport and install even in

locations with difficult access. The compact size of MidD systems provides a logistics

advantage. Flexible installation options are multiplied by the possibility of separating the

battery cabinet from the rest of the system. Delta’s MidD DC series provides typically 5–20

kW of premium-quality electricity; AC series typically up to 6 kVA.

Delta’s CabD DC power series can secure up to hundreds of kilowatts of premium-quality

electricity. The stand-alone cabinets offer an integrated approach to power system architecture.

The modularity and scalability of these easy-to-use systems enable rapid roll-out and easy

expansion. CabD offers the option of parallel installation for maximum capacity, while a single

unit can control the entire system. CabD AC series can secure typically up to several dozen

kVA of premium-quality electricity per cabinet

Delta Site Monitoring and Control System (SMCS) is designed to condition low-quality AC

utility, enhance the availability of AC, and protect equipment from voltage variations and

fluctuations. The SMCS acts as an interface between the AC mains, diesel generator and power

plant to maximize the utilization of AC mains and battery power, and to reduce the running

costs of the diesel generator. Attaching renewable power sources to the system can further

optimize this. A cabinet-type SMCS suits various applications requiring high power and is ideal

for small BTS/BSC installations. The power range is typically 5–25 kVA. SMCS is part of

SolutionE concept.

Following are the products of DELTA in field of Telephone Power Supply

• DPR-48/27000 NSCSU SYSTEM: It provides a max power of 21.6KW constant

power for telecommunication equipment. Upto 4 rectifiers shelves can be in one 19”.A

maximum of 4 shelves can be accommodated in system.Active power correction is >.

99PF.It has got a high power efficiency of >92%.There is a special scheme for

temperature compensation and float voltage for VRLA batteries ,It has got a front

access for ease of access and maintainance.it has got a high power DC distribution. The

system can be equipped with a voltage,current,energy meter which depends on the

customer’s choice.

Fig 1.5: DPR 2700 NSCSU System

Fig 1.6: Internal View

Fig1.7: Alarm PFC terminal of the system

• INDUS48V-4000W-PSC3 SYSTEMIt is equipped with telecom business leading controller

which has got the capability to control site equipment ie : DG/Aircon/Battery/Shelter. It

is user friendly local monitoring with integrated display and keypad.it is equipped with

integrated web server for system monitoring, control and configuration. It is highly

flexible for site expansion. Its is equipped with different access levels with password

protection. Site can remotely be accessed and monitored and Software download. It has

got enhanced battery management and battery test functions .Its has got PLC

functionalities and is equipped with event and data log. Energy saving mode with

rectifier cycling and efficiency mode.it is equipped with CAN bus and has advanced

rectifier functions.

Fig1.8: PSC3 Controller

Fig1.9: Outlook og DPR 4000w System

Fig1.10: Inner view of the system

• INDUSIntegratedPowerManagementSystem(IIPMS):It acts as an interface between

the AC mains power, diesel generator and the power plant in order to maximize the use

of AC mains and battery power and to minimize the operations of diesel generator.it

ensures optimal energy efficiency. It is a complete solution for infrastructure sharing. Its

is designed to condition low quality AC power to improve the availability of AC and

protect equipment from voltage variations and fluctuations. For maximized AC

availability it is equipped with Healthy Phase Selector (HPS) and Static Voltage

Regulator (SVR). It has the ability to maximize energy efficiency so as to manage

genset and control the power of AC when quality of power Is low .It has got fuel

supervision to check schedule refilling. It protects the system for N-Loss by generating

its own neutral when it is not available. It monitors neutral current and maintains it to

neutral current ‘set value’. It has the ability to protect system from Smoke and

lightening failures. There is a mechanical interlock between DG and Mains MCB. It is

site configurable For single and three phase. Dynamic SVR loading feature provides

increased grid condition usage. This system is Tamper proof.

Fig1.11: IIPMS System

CHAPTER 2

SMPS

2.1 Introduction: Power supply is a broad term but this lesson is restricted to discussion of

circuits that generate a fixed or controllable magnitude dc voltage from the available form

of input voltage. Integrated- circuit (IC) chips used in the electronic circuits need standard

dc voltage of fixed magnitude. Many of these circuits need well-regulated dc supply for

their proper operation. In majority of the cases the required voltages are of magnitudes

varying between -18 to +18 volts. Some equipment may need multiple output power

supplies. For example, in a Personal Computer one may need 3.3 volt, ±5 volt and ±12 volt

power supplies. The digital ICs may need 3.3volt supply and the hard disk driver or the

floppy driver may need ±5 and ±12 volts supplies. The individual output voltages from the

multiple output power supply may have different current ratings and different voltage

regulation requirements. Almost invariably these outputs are isolated dc voltages where the

dc output is ohmically isolated from the input supply. In case of multiple output supplies

ohmic isolation between two or more outputs may be desired. The input connection to these

power supplies is often taken from the standard utility power plug point (ac voltage of

115V / 60Hz or 230V / 50Hz). It may not be unusual, though, to have a power supply

working from any other voltage level which could be of either ac or dc type. There are

two broad categories of power supplies: Linear regulated power supply and switched

mode power supply (SMPS). In some cases one may use a combination of switched mode

and linear power supplies to gain some desired advantages of both the types.

2.2 Linear Regulated Power Supply: The basic block for a linear power supply

operating from an unregulated dc input. This kind of unregulated dc voltage is most

often derived from the utility ac source. The utility ac voltage is first stepped down

using a utility frequency transformer, then it is rectified using diode rectifier and filtered

by placing a capacitor across the rectifier output. The voltage across the capacitor is still

fairly unregulated and is load dependent. The ripple in the capacitor voltage is not only

dependent on the capacitance magnitude but also depends on load and supply voltage

variations. The unregulated capacitor voltage becomes the input to the linear type power

supply circuit. The filter capacitor size is chosen to optimize the overall cost and

volume. However, unless the capacitor is sufficiently large the capacitor voltage may

have unacceptably large ripple. The representative rectifier and capacitor voltage

waveforms, where a 100 volts (peak), 50 Hz ac voltage is rectified and filtered using a

capacitor of 1000 micro-farad and fed to a load of 100 ohms. For proper operation of the

voltage regulator, the instantaneous value of unregulated input voltage must always be

few volts more than the desired regulated voltage at the output. Thus the ripple across

the capacitor voltage (difference between the maximum and minimum instantaneous

magnitudes) must not be large or else the minimum voltage level may fall below the

required level for output voltage regulation. The magnitude of voltage-ripple across the

input capacitor increases with increase in load connected at the output. The step down

transformer talked above should be chosen such that the peak value of rectified voltage

is always larger than the sum of bare minimum voltage required at the input of the

regulator and the worst-case ripple in the capacitor voltage. Thus the transformer turns

ratio is chosen on the basis of minimum specified supply voltage magnitude. The end

user of the power supply will like to have a regulated output voltage (with voltage ripple

within some specified range) while the load and supply voltage fluctuations remain

within the allowable limit. To achieve this the unregulated dc voltage is fed to a

voltage regulator circuit. The circuit in Fig.21.1 shows, schematically, a linear

regulator circuit where a transistor is placed in between and the load (here the control

power dissipated in the base drive circuit of the transistor is assumed to be relatively

small and is neglected). The worst-case series voltage drop across the transistor may be

quite large if the allowed variation in supply magnitude is large. Worst-case power

dissipation in the transistor will correspond to maximum supply voltage and

maximum load condition (load voltage is assumed to be well regulated). Efficiency of

linear voltage regulator circuits will be quite low when supply voltage is on the higher

side of the nominal voltagethe unregulated dc voltage and the desired regulated dc

output. Difference between the instantaneous input voltage and the regulated output

voltage is blocked across the collector - emitter terminals of the transistor. As discussed

previously, in such circuits the lowest instantaneous magnitude of the unregulated dc

voltage must be slightly greater than the desired output voltage (to allow some voltage

for transistor biasing circuit). The power dissipation in the transistor and the useful

output power will be in the ratio of voltage drops across the transistor. An 18V (rms),

50 Hz supply is rectified using a full bridge diode rectifier and is followed by a capacitor

filter. The load connected across the capacitor is a simple resistor of 30 ohm. What

should be the value of filter capacitor to get only 5 volts peak to peak ripple across the

load voltage? Neglect voltage drop across conducting diode.

2.3 Switch Mode Power Supply: Like a linear power supply, the switched mode power

supply too converts the available unregulated ac or dc input voltage to a regulated dc

output voltage. However in case of SMPS with input supply drawn from the ac mains, the

input voltage is first rectified and filtered using a capacitor at the rectifier output. The

unregulated dc voltage across the capacitor is then fed to a high frequency dc-to-dc

converter. Most of the dc-to-dc converters used in SMPS circuits have an intermediate

high frequency ac conversion stage to facilitate the use of a high frequency transformer for

voltage scaling and isolation. In contrast, in linear power supplies with input voltage

drawn from ac mains, the mains voltage is first stepped down (and isolated) to the

desired magnitude using a mains frequency transformer, followed by rectification and

filtering. The high frequency transformer used in a SMPS circuit is much smaller in size

and weight compared to the low frequency transformer of the linear power supply circuit.

The ‘Switched Mode Power Supply’ owes its name to the dc-to-dc switching converter for

conversion from unregulated dc input voltage to regulated dc output voltage. The switch

employed is turned ‘ON’ and ‘OFF’ (referred as switching) at a high frequency. During

‘ON’ mode the switch is in saturation mode with negligible voltage drop across the

collector and emitter terminals of the switch where as in ‘OFF’ mode the switch is in cut-

off mode with negligible current through the collector and emitter terminals. On the

contrary the voltage- regulating switch, in a linear regulator circuit, always remains in the

active region. Details of some popular SMPS circuits, with provisions for incorporating

high frequency transformer for voltage scaling and isolation, have been discussed in next

few lessons. In this lesson a simplified schematic switching arrangement is described that

omits the transformer action. In fact there are several other switched mode dc-to-dc

converter circuits that do not use a high frequency transformer. In such SMPS circuits the

unregulated input dc voltage is fed to a high frequency voltage chopping circuit such that

when the chopping circuit (often called dc to dc chopper) is in ON state, the unregulated

voltage is applied to the output circuit that includes the load and some filtering circuit.

When the chopper is in OFF state, zero magnitude of voltage is applied to the output side.

The ON and OFF durations are suitably controlled such that the average dc voltage applied

to the output circuit equals the desired magnitude of output voltage. The ratio of ON time

to cycle time (ON + OFF time) is known as duty ratio of the chopper circuit. A high

switching frequency (of the order of 100 KHz) and a fast control over the duty ratio results

in application of the desired mean voltage along with ripple voltage of a very high

frequency to the output side, consisting of a low pass filter circuit followed by the load.

The high frequency ripple in voltage is effectively filtered using small values of filter

capacitors and inductors. A schematic chopper circuit along with the output filter. Some

other switched mode power supply circuits work in a slightly different manner than the dc-

to-dc chopper circuit.

2.4 SMPS Vs Linear Power Supply: In a linear regulator circuit the excess voltage

from the unregulated dc input supply drops across a series element (and hence there is

power loss in proportion to this voltage drop) whereas in switched mode circuit the

unregulated portion of the voltage is removed by modulating the switch duty ratio. The

switching losses in modern switches (like: MOSFETs) are much less compared to the loss

in the linear element. In most of the switched mode power supplies it is possible to insert a

high frequency transformer to isolate the output and to scale the output voltage magnitude.

In linear power supply the isolation and voltage-scaling transformer can be put only across

the low frequency utility supply. The low frequency transformer is very heavy and bulky

in comparison to the high frequency transformer of similar VA rating. Similarly the output

voltage filtering circuit, in case of low frequency ripples is much bulkier than if the ripple

is of high frequency. The switched mode circuit produces ripple of high frequency that can

be filtered easily using smaller volume of filtering elements. Linear power supply though

more bulky and less efficient has some advantages too when compared with the switched

mode power supply. Generally the control of the linear power supply circuit is much

simpler than that of SMPS circuit. Since there is no high frequency switching, the

switching related electro-magnetic interference (EMI) is practically absent in linear

power supplies but is of some concern in SMPS circuits. Also, as far as output voltage

regulation is concerned the linear power supplies are superior to SMPS. One can more

easily meet tighter specifications on output voltage ripples by using linear power supplies.

2.5 Hybrid Power Supply: A comparison of linear and switched mode power supplies

tells about the advantages and disadvantages of the two. Linear power supply is highly

inefficient if it has to work over large variations in input voltage, is more bulky because of

the use of low frequency transformer and filter elements (inductors and capacitors). On the

other hand linear power supplies give better output voltage regulation. It may sometimes

be required to have output voltage regulation similar to the one provided by linear supplies

and compactness and better efficiency of a switched mode supply. For this, the linear

power supply may be put in tandem with a switched mode supply. Let us consider a case

where one needs an isolated and well-regulated 5 volts output while input power is drawn

from utility supply that has large voltage fluctuation. In such a situation one may generate

an isolated 7.5 volts from an SMPS and follow it by a 5 volts linear power supply set to

work with 7.5 volts input. The input to linear power supply must be few volts more than

the required output (for proper biasing of the switches) and hence SMPS tries to maintain

around 7.5 volts input. It can be seen that the linear power supply now does not have large

input voltage variation in spite of large variations in the utility rms voltage. The SMPS

portion of the power supply efficiently performs the job of voltage isolation and

conversion from widely varying utility voltage to fairly regulated 7.5 volts dc. Under

the given condition it may not be difficult to see that the overall efficiency of this hybrid

power supply will lie between that of a SMPS and a linear supply. The overall cost may

or may not increase even though two supplies in tandem are used. It is to be kept in

mind that to achieve the same output voltage specification by an SMPS circuit alone,

the control and filtering circuit may become more costly and complex (than the one used

in the hybrid power supply unit). Similarly if the linear supply has to be designed for

larger fluctuation in input voltage the component ratings, including heat-sink ratings, will

be higher and may cost as much as the hybrid unit.

2.6 Multiple Output SMPS: A single power supply unit may need to output several

different voltages. The individual output voltages may have different ratings in terms of

output current, voltage regulation and ripple voltages. These outputs may need isolation

between them. Generally a common high frequency transformer links the input and output

windings and in spite of output voltage feedback all the outputs cannot have same

regulation because of different loads connected to different outputs and hence different

ohmic (resistive) drops in the output windings (loads are generally variable and user

dependent). Also the coupling between the different secondary windings and the

primary winding may not be same causing different voltage drops across the respective

leakage inductances. Barring this mismatch in the voltage drops across the resistances and

leakage inductances of the secondary windings their output voltages are in proportional to

their turns ratios. The turns ratios are properly chosen to give fairly regulated individual

output voltages (even if only one output voltage feedback is used for SMPS switch

control). The output that needs to have tighter voltage regulation may be used for output

voltage feedback. In case another output needs to have similarly tight regulation then that

particular output may be passed through an additional linear regulator circuit as in the case

of hybrid power supply circuit discussed in the previous section.

2.7 Resonant Mode Power Supply: Resonant mode power supplies are a variation

over SMPS circuits where the switching losses are significantly reduced by adapting zero-

voltage or zero-current switching techniques. In non- resonant mode SMPS circuits the

switches are subjected to hard switching (during hard- switching, both the voltage and

current in the switch are of considerable magnitude resulting in large instantaneous

switching power loss). Efficiency of resonant mode power supplies is generally higher

than non-resonant mode supplies.

2.8 Power Supply Specification: Power supplies may have several specifications to be

met, including their voltage and current ratings. There may be short time ratings of higher

magnitudes of current and continuous ratings of somewhat lower magnitudes. One needs

to specify the tolerable limits on the ripple voltages, short-circuit protection level of

current (if any) and the nature of output volt-current curve during over-current or short

circuit (the output voltage magnitude should reduce or fold back towards zero, gradually,

depending on the severity of over-current). The fuse requirement (if any) on the input and

the output side may need to be specified. One needs to specify the type of input supply

(whether ac or dc) or whether the power supply can work both from ac or dc input

voltages. Acceptable range of variation in input voltage magnitude, supply frequency (in

case of ac input) is also to be specified. Efficiency, weight and volume are some other

important specifications. Some applications require the electro-magnetic compatibility

standards to be met. By electromagnetic compatibility it is meant that the level of EMI

generation by power supply should be within tolerable limits and at the same time the

power supply should have the ability to work satisfactorily in a limited noisy environment.

It is quite common to have output voltage isolation and it is specified in terms of isolation

breakdown voltage. In case of multiple power supplies it needs to be specified whether

all the outputs need to be isolated or not and what should be the acceptable ripple

voltage range for each In majority of the cases the available source of input power is the

alternating type utility voltage of 50 or 60 Hz. The voltage levels commonly used are 115V

(common in countries like, USA) and 230 volts (common in India and many of the

European countries). Most utility (mains) power supplies are expected to have ± 10%

voltage regulation but for additional precaution the SMPS circuits must work even if

input voltages have ± 20% variation. Now-a-days universal power supplies that work

satisfactorily and efficiently both on 115 V and 230 V input are quite popular. These

power supplies are very convenient for international travelers who can simply plug-on

their equipments, like laptop computer and shaving machine, without having to pay

much attention on the exact voltage and frequency levels of the utility supply. In contrast

some of the other power supplies have a selector switch and the user is required to adjust

the switch position to match the utility voltage. In case user forgets to keep the selector

switch at correct position, the equipment attached may get damaged.

2.9 Some Common Type of SMPS Circuit: There are several different topologies

for the switched mode power supply circuits. Some popular ones are: fly-back,

forward, push pull, C’uk, Sepic, half bridge and H-bridge circuits. Some of these

configurations will be discussed in the coming lessons. A particular topology may be

more suitable than others on the basis of one or more performance criterions like

cost, efficiency, overall weight and size, output power, output regulation, voltage ripple

etc. All the topologies listed above are capable of providing isolated voltages by

incorporating a high frequency transformer in the circuit. There are many commercially

available power supply controller ICs that can readily be used to control the duty ratio of

the SMPS switches so that the final output is well regulated. Most of these ICs are

capable of driving MOSFET type of switches. They also provide features like under

voltage lock-out, output over-current protection etc.

CHAPTER 3

UPS An UPS cum Inverter is an electrical device that converts direct current (DC) to alternating

current (AC). The converted AC can be at any required voltage and frequency with the use of

appropriate transformers, switching, and control circuits. It can be used for both domestic

appliances like fan, tube light, bulb, TV etc as well as for computer. Solid-state UPS cum

Inverters have no moving parts and are used in a wide range of applications, from small

switching power supplies in computers, to large electric utility high-voltage direct current

applications that transport bulk power. UPS cum Inverters are commonly used to supply AC

power from DC sources such as solar panels or batteries. It performs the opposite function of a

rectifier.

3.1 UPS PRINCIPLE: The principle of operating of UPS cum Inverter involves switching

of input voltage at the transformer terminals. Thus DC at the input of transformer becomes

variable. Hence variable flux induces, which produces variable output voltage. The

magnitude of the output depends upon the turn ratio of the transformer. This switching of

input voltage can be generated be generated with the help of transistor and the signal is

amplified to power the transformer. ObviouslythemainuseofanUPScumInverterisonly

for powering common electrical appliances like lights and fans during a power failure

withoutinterruption.AsthenamesuggeststhebasicfunctionofanUPScumInverteristo

invertaninputdirectvoltage(12VDC)intoamuchlargermagnitudeofalternatingvoltage

(generally 110VACor 220VAC). Before learning how to build anUPS cum Inverter, let’s

first understand the following fundamental elements of an UPS cum Inverter and its

operatingprinciple:

• Oscillator: An oscillator converts the input DC (Direct Current) from a lead

acid battery into an oscillating current or a square wave which is fed to the

secondary winding of a power transformer. In the present circuit, IC 4049 has

been used for the oscillator section. • Transformer: Here the applied oscillating voltage is stepped up as per the ratio

of the windings of the transformer and an AC much higher than the input DC

source becomes available at the primary winding or the output of the UPS cum

Inverter.

3.2 TypesofUPS:The range of UPS modules currently available is vast, beginning with ultra

compact desktop units to modules of several hundred kVA. Furthermore, some

manufacturers design UPS modules which can be configured as parallel-controlled multi-

module systems, increasing the total system rating to several thousand kVA – e.g. 2 or

3MVA systems are possible• Micro System: Modules in this power range are typically designed to supply

a single personal computer (PC) workstation and are normally housed in a mini-

tower case about half the size of a typical personal computer system unit. The

UPS is connected to a standard utility mains supply outlet such as a three-pin

13A socket (UK) and due to their small weight and dimensions can be

considered as being portable. Modules at this power level include on-line, off-

line and line interactive designs and provide a single point solution to a

particular power need. Load equipment is usually connected to a standard mains

connector (IEC) on the back of the UPS which is usually protected by a circuit

breaker or fuse. At this power level the batteries are usually integral to the UPS

cabinet, and extended battery cabinets are unlikely to be offered as an optional

extra. Because these modules are designed to be placed adjacent to the load

equipment user it is not generally necessary to provide any remote alarm

facilities to warn the operator of the module’s operational status. However,

current practice might include installing an automatic control interface between

the UPS and computer e.g. SMNP (Simple Network Management Protocol) or

automatic shutdown software• Mini System: Modules in this power range are in many ways similar to the

‘micro’ UPS systems described above in that they are designed for office use

and can be considered to be portable. However, the increased rating makes these

modules suitable to supply a fileserver or a complete workstation comprising a

PC and its peripheral equipment, such as printer (but not a laser printer), scanner

etc. These modules are again connected to a standard utility mains supply outlet

such as a three-pin 13A socket (UK) and can include on-line, off-line and line

interactive designs. The load equipment is usually connected to standard mains

connectors (IEC) on the back of the UPS which are usually protected by a circuit

breaker or fuse, but it is likely that several supply outlets are provided to

facilitate the connection of several small items of load equipment. At this power

level the batteries are usually integral to the UPS cabinet, but some modules

might have provision to connect to additional batteries contained in a purpose

built extended battery cabinet to increase the total battery back-up (autonomy)

time. Where this is the case the battery charger within the module is usually

sufficiently rated to provide the additional battery charging current. However, in

extreme circumstances the extended battery cabinet must include a dedicated

charger system to cater for the additional batteries and will therefore also require

connecting to the mains supply. As with the ‘micro’ UPS systems, it is not

generally necessary to provide any remote alarm facilities for this size of UPS

due to the close proximity of the system to the load operator. However, as with

‘micro’ systems, SNMP or automatic shutdown software may well be a

requirement depending upon the criticality of the load.

3.3 Block Diagram of UPS:

Fig. 3.1: Block Diagram of UPS

• Offline Illustration: With this design the critical load is powered from the

bypass line (i.e. raw mains) and transferred to the inverter if the bypass supply

fails or its voltage goes outside preset acceptable limits. During normal

operation the load is subjected to any mains disturbances that fall within the

acceptable bypass voltage ange although most modules of this type include a

degree of spike suppression and rf (radio frequency) filtering in their bypass

circuit. Under normal conditions the battery charger operates continuously to

keep the battery fully charged. n some models the inverter may be turned off to

improve the overall system efficiency, although its control electronics are fully

operational in order to provide a very fast inverter start when called for. If the

bypass voltage falls below a minimum value the inverter is immediately started

(if not already running) and the load transferred to the inverter supply by the

static switch (or output transfer relay). Due to the fact that the bypass supply is

already failing when the transfer sequence is initiated there is an inevitable load

supply break while the transfer takes place, albeit brief and typically in the range

2 to 10ms. Most loads should, however, ride through this period satisfactorily

without adverse affects. The load is re-transferred to the bypass line once the

bypass supply is restored. Due to the inevitable load break during transfer some

purists argue that this type of system is really a form of stand-by power supply

rather than a true UPS. When the load is transferred to inverter in this type of

module the inverter immediately operates from battery power and can sustain

the load only until the battery voltage falls to its end-of-discharge level,

whereupon the UPS output supply will fail if the bypass supply is not restored.

• Line-Interactive System: This type of UPS covers a range of hybrid

devices that attempt to offer a higher level of performance than conventional

off-line designs by adding voltage regulation features in the bypass line. The

two most popular types of system in this category employ either a buck/boost

transformer or a ferroresonant transformer. Like off-line models, line-interactive

UPS normally supply the critical load through the bypass line and transfer it to

the inverter in the event of a bypass supply failure. The battery, charger and

inverter power blocks are utilized in the same manner as in an off-line system

but due to the added ‘regulation’ circuits in the bypass line the load is

transferred to the battery-fed inverter supply less often, making this type of

system slightly more efficient in terms of running costs and battery ‘wear’

compared with an off-line system.

3.4 Circuit Diagram:

Fig.3.2 Circuit Diagram UPS

• Working: This power UPS cum Inverter circuit will provide a very stable

“Square Wave” Output Voltage. Frequency of operation is determined by a pot

and is normally set to 60 Hz. various “off the shelf” transformers can be used.

Or Custom winds your own for best results. Additional MosFets can be

paralleled for higher power. It is recommended to Have a “Fuse” in the Power

Line and to always have a “Load connected”, while power is being applied. The

Fuse should be rated at 32 volts and should be approximately 10 Amps per 100

watts of output. The Power leads must be heavy enough wire to handle this High

Current Draw! appropriate Heat Sinks Should be used on the RFP50N06 Fets.

These Fets are rated at 50 Amps and 60 Volts. Other types of Mosfets can be

substituted if you wish.

3.5 Advantages:

• Quick, steady and accurate providing voltage

• Approximate constant output voltage.

• No noise like generator.

• Instant auto ON and Off operation

• Approximately 80% efficiency

• Customization possible.

3.6 Applications:

• Computers

• Photocopier

• Domestic light

• Testing Laboratory Equipment

• As an emergency light in operation theatre

• Machinery

• Medical Equipment

• Elevators

• Communication Equipment Center