Accelerator Activity
Power Supplies Division - Power Supplies Activities 


Infrastructure and Facilities

High Voltage Laboratory

The reliability and safe operation of a high voltage system depends upon the integrity of its insulation. A high voltage test is essential to examine this integrity and to determine the ability of the insulation to meet its design specifications. In view of this a High Voltage Laboratory has been set up with following objectives:

  • To support the developmental activities of Accelerator Programme requiring high voltage dc and pulsed power supplies.
  • To promote the high voltage and dielectric research activities.
  • To generate systematic practical training among the people working in high voltage fields.

 To support its objectives the RRCAT High Voltage Laboratory is equipped with the following test and measuring equipments:

  • 100 KV, 5 KVA, 50 Hz, PD free testing transformer.
  • 400 KV, 7.5 mA DC voltage source.
  •  420 KV, 740 Joules impulse generator.
  • 500mm, motorized sphere gap assembly.
  • HAGNUK(German) make hand held partial discharge detector.
  • 500 MHZ, Digital Storage Oscilloscope with recorder.
  • 100 kVrms Transformer oil breakdown tester.

400 kV Multi Test Set (AC, DC, and Impulse Generator)

500 kV Sphere-gap Assembly
Conducted EMI measurement setup [ Go to Top ]

The high-frequency switching power conversion systems are known to be more efficient, light-weight and compact than their line frequency and linear counterparts. However, the former generates electromagnetic interference (EMI). The EMI, transmitted in two forms – radiated and conducted, may disturb the normal operation of the other equipments in the vicinity. With increasing use of high-frequency switching power converters for accelerator and laser systems, it becomes important to limit the electromagnetic pollution to facilitate system integration and commissioning. There are various CISPR, IEC, VDE, FCC and Military standards that specify the maximum limit on conducted as well as radiated EMI. A set-up for the measurement of conducted EMI has been established in the Power Supplies and Industrial Accelerator Division.

The equipment under test (EUT), (Indus-2 quadrupole magnet type – 3 power supply in the photograph) is placed on a 12 * 8 feet, 1.6 mm thick ground plane fabricated with aluminum sheets on wooden insulating supports of height 10 cm. For testing of table-top equipments, a wooden table is provided to keep the EUT 0.8 m above the ground plane as specified in the standard. The conducted noise is measured in terms of mains disturbance voltage across a 50 Ω termination impedance of an artificial mains network (AMN) or line impedance stabilization network (LISN) through which the AC mains power to EUT is provided. The LISN defines the line impedance to 50 Ω as seen by the EUT for measurement frequency range of 150 kHz to 30 MHz. A 50 micro-henry / 50 ohm, three-phase, four-wire LISN is installed at the setup for testing of EUTs powered from three-phase as well and single-phase AC mains. An attenuator inbuilt to LISN and additional transient pulse limiter are used for safe measurements on the spectrum analyzer. The interconnections of EUT to mains through LISN and to the load are made as recommended in the standards.

The test setup can also be used for initial functional tests of the power supplies for which a three-phase 100 A auto-transformer, a 12 kVA isolation transformer is provided for reducing the mains voltage and electrical isolation. A low resistance (less than 1 ohm) high current (up to 200 A) load is also installed at the test site. Low conductivity water (LCW) is available for cooling of EUT and load.

The conducted EMI test set-up
The conducted EMI test set-up

In addition to the existing set up for measuring conducted EMI generated by power supplies being fed by three phase input, a set up has also been established for measuring and analyzing the EMI generated by power supplies which are fed by single phase. This setup consists of a Line Impedance Stabilizing Network (LISN) through which the AC mains power to equipment under test (EUT) is provided. The LISN defines the line impedance to 50 ohm as seen by the EUT for measurement frequency range of 9 kHz to 30 MHz. It also consists of an EMI analyzer having measurement frequency range of 9 kHz to 300 MHz. This analyzer separates the conducted noise into two parts: common mode noise and differential noise which can be separately selected and displayed in a spectrum analyzer, thereby facilitating respective filter design. Total EMI noise can also be seen directly by connecting spectrum analyzer to LISN.

Photograph of LISN (bottom), EMI analyzer (middle) and spectrum analyzer (top).
Photograph of LISN (bottom), EMI analyzer (middle) and spectrum analyzer (top).

In order to qualify the immunity of power converters against the electrical fast transients (EFT), a test setup called transient immunity test setup consisting of a EFT generator, coupling - decoupling network and a capacitive coupling clamp has been installed, as shown in the following figure.

Photograph of of the transient immunity test setup.
Photograph of of the transient immunity test setup.
Transformer Facility [ Go to Top ]

Power supplies Division requires special types of transformers viz high current water cooled rectifier transformers, Compact dry type transformers, high frequency transformers, pulse transformers, multiphase transformers, high frequency chokes, etc which are not locally available. To cater these needs of the division and to obviate the delay in procurement of the non-standard and special types of transformers, an in-house transformer facility has been started initially at RRCAT with little infrastructure. Gradually, after taking the factors like quality, economy and special requirement into consideration, the aforementioned facility has been expanded by adding machinery like programmable winding machine [for winding round conductors of size [for 48 to 18 swg], winding machines for winding flat conductors, Transformer oil filtering machine [600 LPH capacity], 100 kV Motorised oil test set, vacuum impregnation system for varnishing coils, baking ovens, etc.

Activities of this transformer facility inter-alia include design, production, repair and development of transformers using different core materials, construction methods, winding techniques, cooling methods and insulating materials and production range encompasses multiphase line frequency transformers (up to 12 phases), current transformers, oil-cooled transformers, high frequency high voltage ferrite core transformers, isolation transformers, chokes, etc. Specifications of some of the transformers and inductors fabricated include 1- Φ 2 kVA 50 Hz 230V/20 KV Transformer, 1 Φ 40 kHz 30 kVA 400V/44kV Oil cooled transformer, 1 Φ 40kHz 60kV/30V 15A Transformer, 93mH 3Amp 60 kV 40.7 kHz inductor for DCA P/s, etc


1-Φ 15 kVA, 40 kHz, 400V/22kV
ferrite-cored  oil-cooled transforme
r

1-Φ 2kVA, 50 Hz, 230V/20kV transformer
Test and Measurement Instruments [ Go to Top ]
The Power Supplies Division is well equipped with latest equipments and software used for power supply development. To list a few:

  •  Software support for PCB artwork designing 
  • Circuit simulation and analysis software such as PSpice, PSIM, Proxy etc.
  • DCCTs of 100A, 300A and 1000A range for precise sensing and calibration of current
  • High-bandwidth current probes
  • Digital storage oscilloscopes, PC scopes with and without isolated channels with bandwidth as high as 500 MHz
  • Spectrum analyzer 300 Hz - 3 GHz  
  • 6.5 digit multi meters
High-voltage and High-Current Pulse Test Unit [ Go to Top ]

A 27kV, 5kA pulse test unit is developed. The purpose of this unit is to provide a high voltage test setup for testing of spares being indented. It will also serve as a platform for testing of sub-systems for further development. Table shows the parameters of the test facility. The photograph shows the unit being used to test and measure the effect of metallic coating on ceramic chambers for kickers. Here the load is the Indus-2 kicker magnet and the peak current for charging voltage 27kV, is 12 kA.

Parameters of high-voltage and high-current pulse test unit

Parameters

Values

Max. test voltage

27kV

Total bank Capacitance

0.3uF

Dummy Load

R-L series

Pulse shape

Damped half sine wave

Pulse rise time

1-1.2 uS

Peak Current

5 kA

HV charger

Pulse charger

LV charger

Fly-back

Photograph of high-voltage and high-current pulse test unit
Mechanical Fabrication Workshop [ Go to Top ]

Required for mechanical assembly of power supplies being developed in Power Supplies Division, mechanical fabrication workshop is well equipped with following major machines:

1) High speed  precision centre lathe machine with following specifications:

  • Centre distance - 1000 mm
  • Centre height - 200 mm
  • Swing over bed - 400 mm
  • Swing over gap - 560 mm
  • Main spindle bore - 42 mm
  • Main motor power in Kw - 4 Kw.

2)  Power Shearing machine with 2.1 m  length and cutting thickness capability of 1270 mm x 2 mm for MS
3)  Bench drilling machine  12 mm drilling capacity  
4)  Manually operated shearing machine for cutting of CRGO cores.

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