ByPyramid Electronics


Inverter changeover control box RCF Drawing AW72411 Alt “e”.
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Ceiling fans 30W BLDC Ceiling fans
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 Distribution Transformer rating 3KVA EL / EOG / 4 – 74 with CS-1

DC-DC converters are electronic devices used whenever we want to change DC electrical power efficiently from one voltage level to another. They’re needed because unlike AC, DC can’t simply be stepped up or down using a transformer. In many ways, a DC-DC converter is the DC equivalent of a transformer.

Typical applications of DC-DC converters are where 24V DC from a truck battery must be stepped down to 12V DC to operate a car radio, CB transceiver or mobile phone; where 12V DC from a car battery must be stepped down to 3V DC, to run a personal CD player; where 5V DC on a personal computer motherboard must be stepped down to 3V, 2V or less for one of the latest CPU chips; where the 340V DC obtained by rectifying 240V AC power must be stepped down to 5V, 12V and other DC voltages as part of a PC power supply; where 1.5V from a single cell must be stepped up to 5V or more, to operate electronic circuitry; where 6V or 9V DC must be stepped up to 500V DC or more, to provide an insulation testing voltage; where 12V DC must be stepped up to +/-40V or so, to run a car hifi amplifier’s circuitry; or where 12V DC must be stepped up to 650V DC or so, as part of a DC-AC sinewave inverter.

In all of these applications, we want to change the DC energy from one voltage level to another, while wasting as little as possible in the process. In other words, we want to perform the conversion with the highest possible efficiency.
An important point to remember about all DC-DC converters is that like a transformer, they essentially just change the input energy into a different impedance level. So whatever the output voltage level, the output power all comes from the input; there’s no energy manufactured inside the converter. Quite the contrary, in fact — some is inevitably used up by the converter circuitry and components, in doing their job.
We can therefore represent the basic power flow in a converter with this equation:

Pin= pout+ Plosses
where Pin is the power fed into the converter, Pout is theoutput power and Plosses is the power wasted inside the converter.


Of course if we had a ‘perfect’ converter, it would behave in the same way as a perfect transformer. There would be no losses, and Pout would be exactly the same as Pin. We could then say that:
Vin x Iin = Vout x Iout

or by re-arranging, we get:
Vout/Vin = In/Iout
In other words, if we step up the voltage we step down the current, and vice-versa.

Of course there’s no such thing as a perfect DC-DC converter, just as there are no perfect transformers. So we need the concept of efficiency, where:


Nowadays some types of converter achieve an efficiency of over 90%, using the latest components and circuit techniques. Most others achieve at least 80-85%, which as you can see compares very well with the efficiency of most standard AC transformers.
Many different types
There are many different types of DC-DC converter, each of which tends to be more suitable for some types of application than for others. For convenience they can be classified into various groups, however. For example some converters are only suitable for stepping down the voltage, while others are only suitable for stepping it up; a third group can be used for either.


Another important distinction is between converters which offer full dielectric isolation between their input and output circuits, and those which don’t. Needless to say this can be very important for some applications, although it may not be important in many others.


In this data sheet we’re going to look briefly at each of the main types of DC-DC converter in current use, to give you a good overview. We’ll start first with those which don’t offer input-output isolation, and then progress to those which do.


Non-isolating converters

The non-isolating type of converter is generally used where the voltage needs to be stepped up or down by a relatively small ratio (say less than 4:1), and there is no problem with the the output and input having no dielectric isolation. Examples are 24V/12V voltage reducers, 5V/3V reducers and 1.5V/5V step-up converters.
There are five main types of converter in this non-isolating group, usually called the buck,boost,busk-boost, cuk and charge-pump converters. The buck converter is used for voltage step-down/reduction, while the boost converter is used for voltage step-up. The buck-boost and Cuk converters can be used for either step-down or step-up, but are essentially voltage polarity reversers or ‘inverters’ as well. (The Cuk converter is named after its originator, Slobodan Cuk of Cal Tech university in California.)
The charge-pump converter is used for either voltage step-up or voltage inversion, but only in relatively low power applications.
Buck converter
The basic circuit configuration used in the buck converter is shown in Fig.1. As you can see there are only four main components: switching power MOSFET Q1, flywheel diode D1, inductor L and output filter capacitor C1. A control circuit (often a single IC) monitors the output voltage, and maintains it at the desired level by switching Q1 on and off at a fixed rate (the converter’s operating frequency), but with a varying duty cycle (the proportion of each switching period that Q1 is

ByPyramid Electronics


Jumper Cable RCF Drawing LW75206 alt C.
Cable Harness for Coaches EDTS 208, Rev-D
Cable Harness for Coaches EDTS 181 Rev-F
Cable Harness for Coaches EDTS 252 Rev-H.
Cable Harness for Coaches EDTS 255 Rev-H
Cable Harness for Coaches EDTS 320 Rev-H
Cable Harness for Coaches EDTS 260 Rev-D
Cable Harness for Coaches EDTS 356
Cable Harness for Coaches EDTS176, Rev-B
Cable Harness for Coaches EDTS216,REV-A
 Cable Harness for Coaches EDTS 251, REV-A
Cable Harness for Coaches EDTS 253, REV-I
Cable Harness for Coaches EDTS 254, REV-I
Cable Harness for Coaches EDTS256, REV-I
Cable Harness for Coaches EDTS257, REV-I
Cable Harness for Coaches EDTS259, REV-D
 Cable Harness for Coaches EDTS263, REV-C
Cable Harness for Coaches EDTS264, REV-C
Cable Harness for Coaches EDTS271, AM-2
Cable Harness for Coaches EDTS316, REV-B
Cable Harness for Coaches EDTS319, REV-B
Cable Harness for Coaches EDTS323
Cable Harness for Coaches EDTS357
Cable Harness for Coaches EDTS138
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24V DC Battery Charger

24V Starter Battery Charger for 500kVA DG set as per RCF

specification number

EDTS-106 [REV.-O] or latest

Typical Specification for 24Vdc Battery Charger
 Power rating 4, 6 and 8 kW 150 amp, 220 amp and 300
Optional power rating 12 and 18 kW
 Part No. #ac supply-hBc8000-24-#kWs
 Supply voltage 380 / 415 / 480 volts 3-phase 30 to 70 hz. Battery charger will accept 320 to 525 Vac3-phase or 376 to 700 Vdc
 Design structure  IGBT phase shifted full bridge
Power factor >0.92 for >50% output load
Phase rotation Insensitive to phase rotation
Inrush current <20 amps peak at 400 Vac input
Output current ramp up
 10 seconds to maximum current
Nominal battery voltage 24 Vdc
Charging battery voltage 27.6 Vdc. (Voltage range 24 to 32 Vdc)
Battery over voltage
36 Vdc
 Charging Algorithm constant current; constant voltage; Trickle
 Equalising voltage 24 to 32 Vdc
Battery charging current Separate current control up to 60 amps in constant current mode, switching to constant voltage mode, switching to trickle charge. remainder of current available for the standing load
Static Output Voltage
0.30 Vdc ±0.05 Vdc from 0 to full load.
Battery temperature
charging current reduced as temperature of  batteries increase above

40ºc. current reduces proportionally to zero as battery temperature approaches 65 ºc

 0 to -50 mV/ ºc
Temperature probe inputs 2 X PT100 inputs (2 or 4 wire)
2 X lM335/aD592 probes
Ripple voltage maximum < 0.5 volts peak to peak at 6 khz
Output Dc filter will be provided
Efficiency 92% Peak current mode detection used to prevent saturation in isolation transformer
Ambient temperature -25 to 60 º c
Active circuit No connection to earth
Overload 100% and current limited
Signal outputs at control
4-20 ma proportional to charging voltage
4-20 ma proportional to charging current
N/O fault contacts available
RS485 serial port Two wire isolated supporting Modbus protocol
Optional access for modifying charging
Optional access to status and fault log
LCD display Optional backlit lcD display visible through front window. lcD to display: charging voltage, charging current, State of charging, constant
current, constant voltage, float charge, Battery temperature, fault status
Mounting location Within vestibule or optional under frame
Protection IP21 internally forced ventilated Or IP65 totally
Weight forced ventilated battery chargers 35 kg Underframe IP65 battery chargers 61 kg
External connections Three military style plugs including mating
cable plugs.
• 3-phase supply input
• 24 VDc output and Data control
• control connections
Voltage surges; lightning Differential mode 2.6 kVp common mode 1.3 kVp for 100 µsec Waveform 1.2/50 µsec

Protective Features

  • I x t overload protection
  • Instantaneous over-current protection 150%
  • Output short circuit protection
  • Earth Fault
  • Under voltage
  • Battery charger over temperature
  • Battery over temperature
ByPyramid Electronics

2.5 KVA

2.5kVA Inverter 110V DC-230V AC Natural cooled under slung inverter RDSO-PE-SPEC-TL-0132-2009-Rev-0 or EDTS 032 Rev-C
2.5kVA Inverter 110V DC-110V AC Bulk for Non-AC passenger coaches RDSO-PE-SPEC-TL-0131-2009-Rev-0

General Description

The 2.5kVA Bulk Inverter is designed and manufactured for use in Indian Railways coaches. The inverter uses MOSFET and IGBT technology to convert a DC nominal 110V supply into an AC single phase 230Vrms 50 Hz power supply for the distributed loads that are installed in the Indian Railways coaches. The inverter operates by boosting the DC input voltage to establish an isolated intermediate dc link voltage, and then pulse-width-modulating this link voltage with a single-phase IGBT bridge to produce a single-phase AC output voltage. The inverter output is internally filtered to produce a pure sinusoidal output waveform.

The Bulk Inverter comprises:

  • Boost Converter Board, containing the Boost Power Stage, the DSP Controller, and the on-card Switch Mode Power Supply (SMPS).
  • Boost Power Stage Series Inductor and Transformer, mounted on a separate heatsink.
  • Output Inverter Board, containing the single-phase Inverter Power Stage, LC-LC filter, and output voltage and current measurement circuitry.
  • EMI Board, containing common-mode chokes and suppression capacitors for mitigation of electromagnetic interference, and the Common- mode Earth Leakage Detection current transformer.

These subassemblies are permanently installed in a specially designed cubicle suitable for installation and operation by Indian Railway. All power switching semiconductors are mounted on potential free naturally cooled heatsinks within the cubicle.

Technical Features
• MOSFET based step-up boost power stage
• IGBT based output inverter power stage
• Input under-voltage & over-voltage protected
• Input over-current protected
• Input current limited
• Sinusoidal Output Waveform
• Output short-circuit protected
• Output over-voltage protected
• Output over-current protected
• Fused Input
• Over temperature protected for both input and output stages
• Earth fault protected
• Controlled DC link voltage
• Low loss/high efficiency operation
• Dust proof cubicle
• Modular design, hence easy maintenance
 • Auto-restart on fault clearance (dependent on fault type and frequency of


• RS232 port provided for parameter updating using a PC

Technical Specifications  
 Input Side
 Rated Input Voltage 230V AC ± 5%, 1 Phase
Minimum Input Voltage 90V DC
Maximum Input Voltage 140V DC + 15% ripple
Output Side
Rated Output Voltage 230V AC ± 1%, 50 ± 0.5Hz
Rated Output Frequency  50Hz. ±0.5%
Rated Output Power 2.5kVA at 0.8pf
Output Waveform Sinusoidal
General Data
 Efficiency  More than 92%
Operating Temp. Range  -5°C to 55°C
Cooling Medium  Natural air cooling
Construction Modular
Protection IP 265 for US Cubicle
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Power panel for SG type AC coaches  Power panel for SG type AC coaches as per RCF Specn. No. EDTS-006, Rev-H, Correction – 1
Fuse Cum Rotary Switch Panel Fuse Cum Rotary Switch Panel Complete With Housing CC72025, Alt-B
Fuse Cum Rotary Switch Panel Fuse Cum Rotary Switch Panel Complete With Housing LB72001, Alt-F
Fuse Cum Rotary Switch Panel Fuse Cum Rotary Switch Panel Complete With Housing EDTS 262 Rev-A, AM-2
Fuse Cum Rotary Switch Panel Fuse Cum Rotary Switch Panel Complete With Housing EDTS209, Rev-C
Fuse Cum Rotary Switch Panel Fuse Cum Rotary Switch Panel Complete With Housing EDTS278
Fuse Cum Rotary Switch Panel Fuse Cum Rotary Switch Panel Complete With Housing EDTS280
Fuse Cum Rotary Switch Panel Fuse Cum Rotary Switch Panel Complete With Housing  EDTS242, Rev-1
Fuse Cum Rotary Switch Panel Fuse Cum Rotary Switch Panel Complete With Housing EDTS322, Rev-1
Fuse Cum Rotary Switch Panel Fuse Cum Rotary Switch Panel Complete With Housing ML 72001, Alt-A
Fuse Cum Rotary Switch Panel Fuse Cum Rotary Switch Panel Complete With Housing MS 72010, Alt-B
Switch Board Cabinet  

EDTS 073, Rev.D


EDTS 103, Rev.D
EDTS 104
EDTS 134
EDTS 355
Wheel Set Earthing Equipment EDTS 101, Rev.C AM-1
Feeder Junction Box EDTS 328, Rev.C AM1
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1 KVA to 60KVA RDSO/PE/SPEC/TL/0023-2001 Rev.0 Amendment No.1

General Description

The 1kVA UPS is designed to provide a conditioned power supply with battery backup for trackside ticketing machines within Indian Railways. The UPS uses MOSFET and IGBT technology to produce a regulated 230V, 50Hz output from a variable input supply. In the event of an input supply failure the UPS sources the output power from 48V DC batteries.

The system provides seamless changeover between mains and battery ‘stand-by’ supply and contains an active bypass, which activates during sustained overload and fault conditions, and a manual bypass for servicing purposes.

A battery charger supplies power to charge the batteries as well as to provide auxiliary power to the system controller.

The UPS contains a power factor correction (PFC) front-end rectifier to maintain a near unity power factor. The PFC stage establishes an intermediate dc link voltage which is pulse width modulated through a single-phase IGBT bridge and output filter to produce a regulated 230V, 50Hz single phase output.

The battery supply is boosted through a current fed push-pull (CFPP) converter and connects to the intermediate dc link voltage in parallel with the PFC output. This enables the CFPP to seamlessly take over supply of the power to the output inverter when the input AC supply is unavailable.

The UPS has an LCD and keypad for set point configuration, dynamic operating condition display and fault checking as well as indicator LEDs that show the current state of operation. In addition a USB port is provided on the front of the UPS for downloading of Fault Status data to a USB Memory stick.

Technical Features
• IGBT Based inverter section
• Filtered AC Output with 1kVA capacity
• Input current limiting capability
• Input and Output Over Current protection
• Over temperature protection
• Output short-circuit protection (and lockout)
• Input Under Voltage & Over Voltage Protection
• DC link voltage monitoring
• Low losses & hence high efficiency operation
• Fused Input
• Modular design, hence easy maintenance
• Provision of fault memory recording for diagnosis & subsequent analysis
of faults
• Provision of USB port for USB Memory Stick data downloading
• Auto-restart on fault elimination (dependent on fault type and frequency of
Technical Specifications  
 Input Side
 Maximum Voltage 300V AC
Voltage Operating Range 140V – 280V AC 1 phase, 50 ± 3Hz
Output Side
Rated Output VoltageI : 230V AC ± 1%, 50 ± 0.5Hz
Output Current : 4.5A
Output Power  : 1kVA @ 0.8pf
Overload maximum 125% load for 10 minutes
150% load for 1 minute
General Data
 Efficiency  More than 90%
Operating Temp. Range  -5°C to 55°C
Cooling Medium  Fan forced air cooling
Construction Modular
Dimension in mm
US Cubicle
468(L) x 200(D) x 275(H)
Protection IP 20 for US Cubicle


The 1kVA UPS unit has the following major functional elements:

  • Input Fuses
  • Power Board
  • Battery Charger Board
  • Front Panel Display/Keypad Board
  • EMI Board
  • DSP Controller Board (permanently attached to the Power Board)
  • Series Resistor
  • Batteries
  • Bypass Switches