Switch Mode Power Converter Section (SMPCS)

Power Converters for Indus Complex

The source of electrons for the Indus Accelerator Complex is a microtron. The electrons are then transported via transport Lline-1 (TL-1) to booster synchrotron, where their energy is further increased. The high-energy electrons are then injected to Indus-1 storage ring via Transport Line-2 (TL-2) and to Indus-2 via Transport Line-3.

SMPCL is responsible for the design, development, installation, operation and maintenance of the following power converters in the Indus Accelerator Complex:

1. Power Converters for Microtron LH/RH Coils, TL-1 Quadrupole and Dipole Magnets
2. Development of Power Converters for Injector Linac
3. Power Converters for TL-1 Steering Coil Magnets
4. Power Converter for Energy Analyzer Magnet
5. Power Converters for TL-2 Dipole Magnets and Indus-1 Quadrupole Magnets
6. Power Converter for Indus-1 Sextupole Magnets
7. Power Converter for Indus-1 Steering Magnets
8. Storage Ring (SR) Quadrupole Magnet Power Converters

System	Magnet (Click on the magnet name for more information about the power converter.)	Output		Stability (ppm)	No.
		V	A
Microtron	LH/RH Coils	12	5	± 1000	2
	Steering coils	70	0.4	± 1000	2
Injector linac transport line	Dipole	18	10	± 100	1
	Quadrupole Type-1	18	10	± 100	4
	Quadrupole Type-2	6	10	± 100	2
	Combined Function	6	10	± 100	10
Transport line-1	Dipole	14	12	± 200	1
	Quadrupole	12	5	± 500	6
	Energy Analyzer	18	10	± 100	1
	Steering Coils	20	0.5	± 1000	8
Transport line-2	Dipole	80	300	± 100	2
	Quadrupole	20	80	± 500	8
Indus-1	Quadrupole	120	300	± 400	2
	Sextupole	26	250	± 1000	2
	Steering Coils	5	10	± 1000	8
Indus-2	Quadrupole Q1	82	170	± 50	8
	Quadrupole Q2	113	170	± 50	8
	Quadrupole Q3	92	170	± 50	8

Power Converters for Microtron LH/RH Coils, TL-1 Quadrupole and Dipole Magnets

The power converters for LH/RH coils of microtron (5 A, 10 V, 2 nos.), TL-1 quadrupole magnets (5 A, 12 V – 6 nos.) and TL-1 dipole magnet (12 A, 14 V, 1 no.) have been successfully developed, installed and commissioned. Topology used is the two switch forward converter operating at 100 kHz switching frequency. The power converter design has been standardized on 6U card, allowing easy interchangeability to reduce downtime of the system. Sufficient spare power converter cards are also provided on site. The power converters are more efficient, lighter and smaller than the previous power converters. Output current stability of all the power converters is better than ±100 ppm.

Photographs of installed TL-1 quadrupole and dipole power converters

Development of Power Converters for Injector Linac

It is proposed to install a 30 MeV injector linac as an alternative for the booster synchrotron. For this project, 17 nos. of power converters are required to energize various magnets like dipole, quadrupole and steering coils in transfer line from linac to booster. Therefore 20 nos. of power converters have been developed including three spares with industry support. These are dc current regulated power converters. Out of these twenty power converters, six nos. are rated for 10 A and 18 V output and fourteen nos. are rated for 10 A and 6 V output. The output current stability of these power converters is within ±100 ppm. The topology used in these power converters is two-switch forward converter operating with variable frequency PWM (VFPWM) control in the range from 20 kHz to 100 kHz. In order to achieve better stability, oven is used in the front end electronics. A polarity reversal scheme has been implemented in order to change the polarity of output voltage. These power converters have the capability to be operated in remote mode. To monitor various signals, a 9-pin D-connector is provided on the fascia plate. The power converters were designed, simulated and prototyped at SMPCL, PCD, RRCAT. After the successful development and evaluation of a prototype power converter, 20 nos. of such power converters have been developed at ECIL, Hyderabad, wherein production, assembly, testing and evaluation was carried out. Each power converter is standardized on a 6U card and five such power converters are housed in one 6U, 19-inch sub-rack as shown in Fig. Three sub-racks are mounted inside a 36 U cabinet.

Photograph of injector linac power converters

Power Converters for TL-1 Steering Coil Magnets

The power converters for TL-1 steering coil magnets are rated for 500 mA and 20 V maximum. A MOSFET-based linear regulator scheme has been selected for this power converter due to low power rating and to maintain simplicity. However, the architecture of the power converter has been designed keeping maintainability, interchangeability and availability of on-site spares in mind. Accordingly, each power converter has been designed on a single 3U size PCB, with full-function feedback control and local-remote operation interface electronics on the same card, for standard 19-inch rack assembly. A common multi-secondary step-down transformer is used to provide necessary ac input voltage to each power converter card, wherein it is rectified, filtered and fed to the MOSFET linear regulator.

Photograph of TL-1 steering coil power converter sub-rack installed and operational in Indus Accelerator Complex

Power Converter for Energy Analyzer Magnet

The power converter for energy analyzer magnet is rated for 10 A/ 18 V output with output current stability of ±100 ppm. The topology used is two-switch forward converter operating with variable frequency PWM (VFPWM) control in the range from 20 kHz to 100 kHz. In order to achieve better stability, oven is used in the front end electronics. This power converter has the capability to be operated in remote mode. To monitor various signals, a 9-pin D-connector is provided on the fascia plate.

Photograph of 10A/18V energy analyzer magnet power converter

Power Converters for TL-2 Quadrupole Magnets

There are 8 quadrupole magnets in TL-2 which are powered by 8 independent converters of rating (80 A, 25 V) which have been successfully installed and commissioned. Topology used in these converters is two switch forward converter operating at 50 kHz switching frequency. Each of the power converters is housed in one 4U rack and eight such power converters are housed in two 24 U cabinets. Each cabinet also has the provision for one spare power converter for easy replacement in case of problem to minimize the machine downtime.

Photograph of installed TL2 quadrupole magnet power converters

Power Converters for TL-2 Dipole Magnets and Indus-1 Quadrupole Magnets

These newly developed power converters s (300 A, 120 V maximum) have been successfully installed and commissioned. The new power converter is developed using a novel full-bridge zero-voltage-switching (ZVS) converter in which the IGBTs are operating at 25 kHz. The converter has a passive adaptive energy storage circuit. When the output current is set at the lower values resulting in low stored energy in the leakage inductance., the auxiliary circuit stores more energy. On the other hand, when the output current is set at the higher values resulting in sufficient stored energy in the leakage inductance to achieve ZVS, the auxiliary circuit stores less energy. Thus the ZVS over full range is achieved without increasing the conduction loss. Output current stability is measured to be better than ± 40 ppm, which is well within the specification of ± 400ppm.

Photograph of installed Indus-1 quadrupole magnet power converters

Power Converter for Indus-1 Sextupole Magnets

The power converters for the main winding of sextupole magnets in Indus-1 are rated for 25 V/200 A and are based on six-pulse thyristor rectifier topology.

Photograph of Indus-1 sextupole magnet power converter

Power Converter for Indus-1 Steering Magnets

These power converters for the steering coil are rated for 10 A and are based on linear regulator using transistor.

Power Converters for Indus-2 Quadrupole Magnets

Two topologies have been followed for the development of power converters for quadrupole magnets of Indus-2. At present, the power converter for Q1 and Q2 type quadrupole magnets are developed using transistor series pass scheme with twelve-pulse SCR rectifier as pre-regulator whereas the power converters for Q3 type quadrupole magnet are developed based on two-switch forward converter topology, in which two stages of two-switch forward converters (each rated for 60 V, 180 A) are connected in input-parallel and output-series configuration. This resulted in modular and smaller units, better thermal management, simpler configuration, smaller filtering requirements and better layout for easy maintenance.

Power Converters for Indus-2 Quadrupole Magnets

Photograph of installed power converters for Q1 type magnets in Indus-2

Photograph of installed power converters for Q2 type magnets in Indus-2

Photograph of installed power converters for Q3 type magnets in Indus-2