|Title of Invention||
"AN INTRINSICALLY SAFE UNINTERRUPTED POWER SUPPLY FOR USE IN HAZARDOUS AREAS"
|Abstract||The present invention relates to an intrinsically safe uninterrupted power supply for use in hazardous areas. The power supply of the present invention is specifically suitable for providing DC powers at different ratings such as +5V 500mA, ±12V 100mA and ±15V 100mA torn various electronic gadgets/ instruments/ sensors installed in hazardous environments such as underground coal mines, oil industries, fertilizer and steel plants, where there are chances of explosion.|
|Full Text||The present invention relates to an uninturrupted power supply,for uno inThe power supply of the present invention is specifically suitable for providing DC powers at different ratings such as +5V 500mA, ±12V 100mA and ±15V 100mA to various electronic gadgets/ instruments/ sensors installed in hazardous environments, such as underground coal mines, oil industries, fertilizer and steel plants, where there are the chances of explosion.
Intrinsically safe uninterrupted power supply is required for running electronic equipment, process equipment, sensors, signal conditioners, transmitters (both digital data and voice communication and sensors signal system) display and audio-visual alarm systems working in highly inflammable as well as hazardous areas falling in category of group I, IIA, IIB and IIC of BIS 5780, 2148, 1309, which are very sensitive to gas/air mixture explosion.
Application of instrumentation in a complex or in a widely distributed system of large industry is difficult, specially in hazardous category of industry under group I, group IIA, group IIB and group IIC, (BIS 5780/2148) where chances of gas mixture explosion always remains. A number of hand held instruments, which are intrinsically safe are
available for measurement of various industrial parameters. Subsequently, these measurements are adopted for better productivity and safety in industry. In such instruments, some form of replaceable or rechargeable batteries are employed. Further, this power source is to be converted in the form which comply with intrinsic safety standards, otherwise it is not permissible to be used in above mentioned categories of industries.
But when we intended to develop or employ an electronic equipment, in distributed network for a complex or large integrated industry, we find virtually there is no standard power source for instrumentation in highly hazardous and explosion prone inflammable areas. Even for simple electronic instrumentation, which are supposed to be operated on continuous basis, no proper power source is available for them. Even if available, they are mostly of dedicated in nature, which cannot be used as a power source for other system in general. In battery power supply, which are normally used in hazardous areas it has been found that no body bothers about health condition of battery employed in the power pack and it gets quickly damaged, thus resulting in a major draw back of non availability
of power supply at the required time.
Prior art of the uninterrupted power supply:
Presently, almost all the hand held instruments employ dry cells for powering its electronic circuitry. These instruments are operated as and when required. For instruments/equipment, which operates on continuous basis mostly have dedicated power sources, this can not be used as a power source for other systems in general. Moreover, these dedicated power supplies do not feed uninterrupted power.
In most of the cases we have found, whenever, there is any need of power for instrumentation or communication, the designer have made provision to tape 110V/230V/550V using approved FLP enclosure having power supply circuitry, designed as per need in industry, they do not have any integrated type of universal uninterrupted power pack as per standard BIS 2148/5780.
Thus main drawback is that they feed power as long as there is mains supply, but during power failure the system is inoperative. On the other hand, the available intrinsically safe battery based power supply, it has been found that, the batteries get quickly damaged due to negligence in monitoring of battery's voltage condition, thus resulting in a major draw back of non
availability of power supply at the time of actual need.
However, when we intend to employ an electronic equipment in distributed network for a large or complex industry on continuous basis, we find that virtually there is no standard power supply, which can feed uninterrupted power at different ratings to different electronic gadget simultaneously.
The main object of the present invention is to provide an Intrinsically Safe (I.S.) Uninterrupted Power Supply (UPS) for use in hazardous areas which obviates the draw backs of the hitherto known power supplies.
Another object of the present invention is to provide an intrinsically safe and uninterrupted power supply capable of supplying DC powers at various ratings such as +5V 500mA, ±12V 100mA and ±15V 100mA.
Yet another object of the present invention is to provide an I.S. and U.P.S capable of working on AC power source of 110V AC or 550V AC with rechargeable battery backup.
The power supply of the present invention is an universal type of uninterrupted DC power supply, which can feed any type of intrinsically safe DC power
required to run electronic gadgets in hazardous areas. Whereas what is commonly available, each instruments, has its own dedicated power unit, one is not suitable for other type of instrumentation.
The power supply of the present invention incorporates an intelligent battery monitoring system, which keeps monitoring the condition of rechargeable battery. The moment battery voltage reaches a pre-determined cut-off voltage, it stops delivery of power and undergoes fast charging. Whenever battery is over charged fast charging is changed to trickle mode of charging.
The power supply of the present invention consists of:
i. Flameproof enclosure
ii. Intelligent charger for rapid charging a rechargeable battery and intrinsically safe power supply units.
The details of the present invention are as follows:
The flameproof enclosure, has been designed with a view to get minimum dimension and weight. This can withstand internal pressure generated by gas mixture explosion. It has minimum flame path, so that explosion
inside is incapable of igniting external explosive gas mixture. It complies with all necessary specifications laid down in IS 2148 for flameproof enclosure.
The enclosure is made up of mild steel sheet having minimum thickness of 6 mm after final machining. It has four separate compartments for housing isolation switch, isolation transformer} maintenance free rechargeable battery and intelligent charger with intrinsically safe DC power supply output box.
In addition it has a cable gland fastening arrangements, inlet for cable sealing material, cable gland box, hanger clamp and flame paths for quenching of flames.
The 110V AC or 550V AC voltage is supplied through cable sealing box for group I industry like coal mines. In addition to this cable sealing box. With little modifications, this developed enclosure can be used for group IIA, IIB, IIC inflammable industries. It has another chamber, where all intrinsically safe DC power supply are available and can be taken through cable for necessary intrinsically safe power to electronic instrumentation.
The power supply of the present invention consists of AC-DC Converter to supply DC-Power for
battery charging as well as DC-DC Converters, which provides an intrinsically safe power supply.
In fig. 1 of the drawing accompanying this specification the block diagram of power supply of the present invention is shown. This consists of (1) input line filter section, (2) line rectifier and filter section, (3) switching circuit with pulse width modulation section, (4) rectifier and filter section, (5) constant current battery charger section, (6) DC-DC conversion section and (7) rechargeable battery section.
Accordingly the present invention provides an uninterrupted power supply which comprises a conventional flameproof cable connector for connecting AC power line of 110V AC or 550V AC to an input line filter circuit (1) through an isolator switch and an isolation transformer, the output of the said input line filter circuit (1) being connected to the input of a line rectifier and filter circuit (2) the filtered DC outputCharaterized in that
of the said line rectifier and filter circuit (2)1 being connected to input of a switching circuit (3) having pulse width modulation, the output of switching circuit (3) being connected to the input of a rectifier and filter circuit (4), the DC output of the said rectifier
and filter circuit (4) being connected to the input of a costant current battery charger circuit (5), the said constant current battery charger circuit (5) being provided with two outputs, one of the said output being connected to a dry rechargeable battery (7) and the second output being connected to a DC-DC conversion circuit (6), capable of providing intrinsically safe DC power output the output of the said battery (7) being also connected to input of the said DC-DC conversion circuit (6)j the said DC-DC conversion circuit (6)
being provided with a devider network, the output of which being connected in a feedback loop to switching circuit (3), the above said individual components and circuits being housed in a flameproof enclosure.
AC input of 110V AC or 550V AC voltage is applied to input line filetter (1) through fuse for inside protection.
This AC voltage is rectified and filtered (2) which is then connected across switching MOSPET. MOSFET is switched by pulse width modulation (3) controlled 1C. When MOSFET is ON, voltage is applied to the primary of the power transformer of the switching circuit. Due to flyback action of is induced in the secondary of the power transformer during MOSFET's OFF
period. This secondary voltage is then rectified and filtered (4).
The output of the AC/DC converter (1,2,3,4) is then passed through switched mode intelligent fast charger controller of constant current battery charger circuit (5) to charge a dry rechargeable battery such as 12V Ni-Cd battery. The said controller senses the negative doubt slope of the battery voltage after full charge and after detecting it, charger goes to 'Trickle Charge Mode'. In this mode the battery charges at trickle charge current.
The DC output through battery charger then passes through battery under voltage cut-off circuit and battery reconnect voltage circuitry and after that it is fed to DC-DC converter (6). The under voltage cut¬off circuitry protects the battery from discharging below a certain set voltage level.
Pulse width of the switching MOSFET can be varied according to the feedback received from the output through the divider network mentioned above.
The DC-DC converter works on flyback topology. It consists of several intrinsically safe DC power outputs.
All the above outputs are Bade to co»ply with the
intrinsic safe standards laid down in IS 5780. These
outputs can be used to power any digital or electronic circuits located in inflammable, hazardous or explosion
The following examples are given by the way of
illustrations and should not be contrued to limit the
scope of the present invention.
The power supply of the present invention was tested at nominal input voltages of 110V AC (±15V) and the test result were found satisfactory. The test observations are shown in the tables
given below: Table – I
Table – II
Table - III
Input Voltage (AC)125V AC
Example II (A) Consideration for Intrinsical, safety;
Mains transformer of the power supply has been isolated by providing earth metal screen between primary and secondary. The core of this supply transformer has been earthed. Both the 110V and 550V AC input lines have been provided with 0.2A and 0.05A fuse respectively. The 110V AC secondary has been provided with 0.2A fuse in both line.
Input and output windings of mains transformer could withstand a test voltage of 1000V AC for 1 minute. Input winding and core could withstand a test voltage of 1000V AC for 1 minute. Other transformers used in the power supply could withstand a test voltage of 1500V AC for 1 minute between primary and secondary windings.
All the component of power supply are housed inside a Flameproof (FLP) enclosure, which has been developed and tested separately as per BIS 2148 for the present development. The output leads which come out of the FLP are as follows:
1. ±15V lines with 63mA fuse, zenor diode and 75 ohms/10 Watt current limiting resistors (CLR)
2. +.12V lines in each time with 63mA fuse, zener
diode and 60 ohms/ 10 Watt current limiting resistor in each line.
3. +5V line with 100mA fuse zener diode and 50 ohms/
4. +5V line with 250mA fuse, zener diode and 15 ohm/
10 Watt CLR.
5. +5V line with 250mA fuse zener diode and 15 ohm/
10 Watt CLR. All the above supply lines have common ground.
B. SPARK TEST
All the above five output supplies coming from the enclosure where tested separately one by one in spark test apparatus with Group IIA Gas (Hydrogen) mixture. There was no ignition of the above gas mixture in any case. The +15V and -15V supply terminals (i.e. 30V) were also tested with above gas mixture. There was no ignition. With + 12V and -12V (i.e. 24V) supply terminals, there was no ignition in spark test apparatus.
All the current limiting resistors (CLR), zener diodes used for current and voltage limitation respectively are found to be adequately rated to meet
the compliance criteria of I.S.5780.
Hence all the above five output supply lines coining out of the FLP enclosure are considered to be intrinsically safe for Group I Gas, vide test certificate no. CMRI/TC/H840, dated July 22, 1996.
The uniterrupted I.S. power supply was installed at Jitpur Colliery for field performance study.
The output supply lines were connected to various electronic gadgets of CMRI-ECOM for feeding power.
Electronic gadgets of CMRI-ECOM consists of (a) CPU Board, (b) Mux 64 Board, (c) Terminal Card I & II, (d) RSS 422, (e) Optical isolator, (f) 64 Channel LED Matrix Board, LCD display Module and Audio Alarm.
The performance of the uninterrupted IS power supply was found to be very satisfactory. All the gadgets connected to this power supply are performing satisfactorily since one and half year till date continuously at the actual working site at Jitpur Colliery of IISCO, at the highest level noise, dust and vibration.
The main advantages of the present invention are: 1. It is an universal intrinsically safe
uninterrupted DC power supply for underground
mine and other hazardous industries consisting both FLP enclosure and intelligent battery charger.
2. Intelligent current sensor for current limit and
short circuit protection.
3. All outputs of UPP is intrinsically safe.
4. Flameproof enclosure of UPS having 30mm flame
path and 0.001mm clearance to make the system
light weight, even after stringent standards.
5. Separate flameproof chambers for each individual
components like, isolation switch, isolation
transformer, battery and electronic gadgets.
6. Light weight and compact in size comparison to
existing FLP enclosure.
7. It is a versatile and universal instrinsically
safe uninterrupted DC power supply which can be
used to power any low power electronic or digital
gadgets available in the world like,
microprocessor or micro controller based gadgets,
which operates continuously in any inflammable
areas. It is used to operate gadgets which
transmit data from unsafe to safe area, which can
annunciate alarm in case of any emergency.
1. An uninterrupted power supply for use in hazardous areas which
comprises a conventional flameproof cable connector for connecting
AC power line of 110V AC or 550V AC to an input line filter circuit (1)
through an isolator switch and an isolation transformer, the output of
the said input line filter circuit (1) being connected to the input of a
line rectifier and filter circuit (2), the filtered DC output of the said
line rectifier and filter circuit (2) characterized in that it being
connected to input of a switching circuit (3) having pulse width
modulation, the output of switching circuit (3) being connected to the
input of a rectifier and filter circuit (4), the DC output of the said
rectifier and filter circuit (4) being connected to the input of a constant
current battery charger circuit (5), the said constant current battery
charger circuit (5), being provided with two outputs, one of the said
output being connected to a dry rechargeable battery (7) and the
second output being connected to a DC-DC conversion circuit (6)
capable of providing intrinsically safe DC power output, the output of
the said battery (7) being also connected to input of the said DC-DC
conversion circuit (6), the said DC-DC conversion circuit (6) being
provided with a divider network, the output of which being connected
in a feedback loop to switching circuit (3), the above said individual
components and circuits being housed in a flameproof enclosure.
2. An intrinsically safe uninterrupted power supply for use in hazardous
areas substantially as herein described with reference to examples
and drawing accompanying this specification.
|Indian Patent Application Number||2154/DEL/1998|
|PG Journal Number||10/2008|
|Date of Filing||24-Jul-1998|
|Name of Patentee||COUNCIL OF SCIENTIFIC AND INDUSTRIAL RESEARCH|
|Applicant Address||RAFI MARG, NEW DELHI - 100 001, INDIA|
|PCT International Classification Number||H02M 3/00|
|PCT International Application Number||N/A|
|PCT International Filing date|