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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