| 25KVA 3 Phase Inverter
for AC Coaches |
|
This is an inhouse developed 25 KVA
IGBT based Inverter for Railway Air Conditioned coach application. This supplies 3-phase
power to the Air Conditioner mounted on the coach. This is mounted below the coach.
Traditionally onboard inverters were being used in Indian Railways. They have switched
over to under slung version, to save space in the coach. MIN253U is a rugged and reliable
inverter having customised to typical Railway environment. |
| The inverter accepts
110V DC supply from the combination of battery bank and self-generator mounted under the
coach. The 110V DC is first stepped-up to higher level DC using IGBT based High Power
Boost Chopper, which will maintain a constant DC link voltage suitable to derive 3-phase
415V/50 Hz supply. This high voltage DC is fed to a 3-phase PWM sine-wave Inverter to get
3-phase output. The 3-phase output is passed through harmonics filter. A micro controller
is used to control the entire system. System operating parameters are monitored
continuously on pulse-by-pulse mode. In the eventuality of any malfunction in the system,
it will shut down the converter and an audiovisual alarm is initiated indicating the
nature of fault. All the faults are logged into a non-volatile memory for lateral
retrieval and corrective action by the maintenance staff. The system is designed to
withstand over load and short circuit. |
| The Inverter is a high
tech product. It is engineered and assembled in rugged and IP65 Level sealed cubicle.
Special care has been taken for thermal management so that even with completely closed
cubicle, heat generated in the system is efficiently driven out keeping internal ambient
relatively cool. It is virtually maintenance free. The converter can withstand harsh
railway environment of sub zero temperature to an ambient of 55°C. It can function
normally even if it is submerged partially in muddy water. The Inverter is designed to
operate continuously for days together. |
| 180 KVA
Static Converter for Electric Locomotives |
|
This is an Auxiliary converter for
Electric Locomotive. Auxiliary power is the most critical for the operation of locomotive.
This power will run air compressors, main transformer cooling pump motors, Traction motor
blowers, etc. |
| Medha has developed
180KVA Auxiliary Converter with Technical Collaboration with Powernetics Ltd, UK, a
leading supplier of Power Converters for European Railway systems. Broadly this system
consists of IGBT based Unity power factor input rectifier, DC to 3 phase Sine wave PWM
Inverter. The unit is protected against overloads and short circuits. The system is forced
air cooled and designed to perform in harsh railway environment. It is highly
sophisticated as well as rugged. |
| Intergrated Power Supply System |
|
Railway safety depends on reliable signaling
system. The basic requirement for any signaling system is a reliable power supply. But
considering power cuts and fluctuations encountered in the incoming power, achieving a
reliable and continuous signaling system is a difficult task. To overcome this problem
railways are looking for a reliable and multiple output power supply scheme with redundant
modules for each output. |
| Medha has worked on this
task and developed an Integrated Power Supply system Type MIP 100. It is a complex,
multiple power output scheme, which eliminates various battery chargers and independent
power supplies, being used traditionally for different signal installations within a
station. This hi-tech power supply will provide power for different loads of a complex
railway station, for its signaling network and protection systems. This highly reliable
power supply with various SMPS based Float cum Boost chargers, DC-DC converters and
inverters, with supervisory control, ensures continuous power supply for all connected
loads, irrespective of power fluctuations and power failures. Proper current sharing
between the modules and inbuilt redundancy will ensure that even if a module fails, its
redundant module continues to operate and provide required power to meet the requirements
of highly demanding railway signalling systems. |
| This equipment is
completely developed indigenously. This power supply will be a great boost for Indian
railway safety system. |
| Audio Frequency Track Circuit |
|
A Track Circuit basically detects
the occupancy of a railway track section, which is an essential part of any modern
signaling system in Railways. Traditionally DC track circuits are being used by Railways,
which are the simplest form of a track circuit. Various other types of Track Circuits like
AC Track Circuit, Pulsed High Voltage Track Circuit, High Frequency Track Circuit, Axle
Counters, etc. have come into use, but each one of them has its own limitations and hence
not widely used. |
| With continual
improvement in Railway technology, rails are being welded to maximise passenger comfort
and safety. But the welding of rails is not suitable for existing DC Track Circuits, where
breaks in rails are must to achieve electrical discontinuity (for isolation). This
contradictory requirement has a solution with the latest technology. The latest
technology, better understanding and manipulation of electrical signals led to Audio
Frequency Track Circuit (AFTC). This circuit works on Audio Frequency signal propagation
and impedance variation principle. This system can reliably work with continuous rails,
with very high reliability. This enables comfortable and safe commutation for railway
passengers. |
| Some of the major
suppliers of AFTC are Alstom, Germany, Bombardier Transportation, Switzerland, Seimens,
Germany, and Union Switch & Signal, Australia. Medha is now poised to enter this
select group in the world, with its in-house developed AFTC type MTC120. |
| Plasma
Systems |
| The concept of an
ionised plasma field dates back to 1856. Plasma is a gaseous environment in which there
are enough ions and electrons, which enable appreciable electrical conductivity. Mostly
plasma is produced in vacuum environment where the gas pressure is less than the ambient. |
 |
Plasma environment is highly
efficient and most appropriate for various types of surface modifications. Some of the
major applications of plasma-based process are: |
- Physical Vapour Deposition (PVD): In which the metal component
of the coating is produced from solid, in a high vacuum environment.
- Plasma Enhanced Chemical Vapour Deposition (PECVD): In which
the components of the coating (ex. titanium and nitrogen) are supplied in gaseous form,
and the thermos chemical reaction to form the coating is produced on the surface of the
tool.
- Sputtering: In which ionised argon bombards the deposition
metal target and extracts the atoms required for coating forming reaction.
- Plasma-based ion implantation: Which is a technique developed
in the late 1980s. The principle of operation is that the object to be ion-implanted is
immersed in plasma and biased with a high-voltage power supply.
|
|
A sheath forms around the object
and ions are accelerated across the sheath into the surface of the immersed object. With
the help of above processes :· |
- Medha can achieve plasma ion-nitriding of industrial
components, which will enhance their wear resistance, and long useful life.
- Medha can deposit single layer, multi layer cuttings on
cutting tools, drill bits, etc. to increase their useful life by 3 to 5 times.
- Medha can deposit decorative and wear resistance hard
coatings, on watchstraps, door hardware, plumbing fixtures, fashion items, and other such
applications.
|
|
Knowing the potential requirement
of plasma systems Medha has indigenously developed plasma generating power supplies, for
various types of plasma processing systems. |
| Solid State
Resonant Inverters for Induction Heat Treatment/Brazing/Melting |
| Induction heating is a
most efficient and versatile technique for inducing heat into a job. It is being used by
industry from age-old spark gap generated RF systems. Then came Rotary Medium Frequency
generators, Valve Oscillators and Thyristorised inverters. But all of them have lower
efficiencies and each of them is suited for only a particular application. The development
of Insulated Gate Bipolar Transistors (IGBT) and their popularisation in the last decade
was major boost in the field of high frequency power conversion at higher power levels. |
|
Medha has developed wide range of
custom-made voltage source and current source Induction heating systems with IGBT/MOSFET
based Resonant Inverters for various induction heating applications. IGBT based inverters with power levels up to 100 KW and output frequencies up
to 450 KHz are made. |
| These inverters have
very high conversion efficiencies of about 95%. Resonance inverters offer short circuit
proof output characteristics enabling very high reliability. Phase locked loop control
scheme ensures unity power factor load matching for maximum power coupling during entire
temperature cycle. Output power can be varied from 10% to 100%. PLC controller along with
Scanner interface is provided for automatic heat treatment cycle. |
| Advantages
of Solid State Induction Heating |
- Maximum repeatability
- Faster cycle time
- High Reliability
- Economical
- Less Cooling Water Requirement
- Low Voltage Operation
|
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