Tens kilowatts power Tens kilowatts power supply based on half-supply based on half-bridge inverter with bridge inverter with

zero current zero current commutationcommutation

A.V. Akimov, A.A. PachkovA.V. Akimov, A.A. Pachkov

For the pulse power supply of For the pulse power supply of the VEPP-5 injector klystrons the VEPP-5 injector klystrons the 40 kW, 50 kV modulators the 40 kW, 50 kV modulators

are usedare used TThe modulator’s pulse forming he modulator’s pulse forming

network (PFN) charge is provided network (PFN) charge is provided by the resonant charging schemeby the resonant charging scheme

the resonant charging scheme the resonant charging scheme comprises such bulky parts as the comprises such bulky parts as the

step-up mains transformer (25 kV), step-up mains transformer (25 kV), the filter capacitor (9 the filter capacitor (9 F, 25 kV), the F, 25 kV), the

charging inductor (20 H)charging inductor (20 H)

PFN charge voltage depends on PFN charge voltage depends on the repetition rate of the the repetition rate of the

modulator. At the repetition rate 1 modulator. At the repetition rate 1 Hz the voltage on PFN decreases Hz the voltage on PFN decreases

to the 70-80 % of the nominal to the 70-80 % of the nominal level, it occurs because of the level, it occurs because of the discharge through the leakage discharge through the leakage

resistors of the scheme elementsresistors of the scheme elements

Today the most developed and widespread system Today the most developed and widespread system providing the capacitive storage devices charge up providing the capacitive storage devices charge up to the voltages of dozen kilovolts at the power of to the voltages of dozen kilovolts at the power of

dozen kilowatts are the power supplies based on the dozen kilowatts are the power supplies based on the full-bridge serial resonant inverters. The full-bridge serial resonant inverters. The

manufacturers of such the power supplies estimate manufacturers of such the power supplies estimate they efficiency at the level 85-92% at the different they efficiency at the level 85-92% at the different

output poweroutput power

Full-bridge serial resonant Full-bridge serial resonant inverterinverter

The main features of the full-bridge The main features of the full-bridge serial resonant inverters are:serial resonant inverters are:

- partial charge of the capacitive - partial charge of the capacitive storage device with the little energy storage device with the little energy doses which are supplied at the doses which are supplied at the frequency of dozen kilohertz;frequency of dozen kilohertz;

- application of the step-up - application of the step-up transformer leakage inductance transformer leakage inductance together with the additional together with the additional capacitor as the elements of the capacitor as the elements of the serial resonant circuit;serial resonant circuit;

- use of the four IGBT switches for - use of the four IGBT switches for the full-bridge invertor;the full-bridge invertor;

- application of the IGBT’s embedded - application of the IGBT’s embedded free-wheel diodes as the essential free-wheel diodes as the essential inverter circuit elements;inverter circuit elements;

- zero current switch turning-on;- zero current switch turning-on; - nonzero current switch turning-off - nonzero current switch turning-off

at low switch voltage;at low switch voltage; - high precision charge stabilization - high precision charge stabilization

at wide voltage range.at wide voltage range.

Half-bridge inverterHalf-bridge inverter This topology allows to This topology allows to

achieve both the turning-on achieve both the turning-on and turning-off of the and turning-off of the switches at the zero current switches at the zero current condition. condition.

Half-bridge inverter seems to Half-bridge inverter seems to be preferable due to the only be preferable due to the only two switch equipment, it two switch equipment, it lowers both the inverter costs lowers both the inverter costs and the switching loses. and the switching loses.

Half-bridge inverter operation Half-bridge inverter operation in the proposed regime does in the proposed regime does not need the free-wheel not need the free-wheel diodes employment. diodes employment.

In other respects the half-In other respects the half-bridge inverter is similar to bridge inverter is similar to the full-bridge inverter.the full-bridge inverter.

PS for the 200 PS for the 200 keV VEPP-5 keV VEPP-5 electron gun electron gun

power supply was power supply was developed. developed.

It has provided It has provided 90% efficiency at 90% efficiency at the 300 W, 3 kV the 300 W, 3 kV

operationoperation

Next PS prototype test Next PS prototype test stand let us to achieve the 2 stand let us to achieve the 2 kW output power at the 20 kW output power at the 20

kV output voltagekV output voltage

10 kW, 40 kV step-up 10 kW, 40 kV step-up transformer was usedtransformer was used

Power modulePower module IGBT half-bridge IGBT half-bridge

module module SKM300GB125D SKM300GB125D (Semikron) (Semikron) designed for the designed for the 300 A (DC 300 A (DC current), 1200 V current), 1200 V operationoperation

Polypropylene Polypropylene capacitors K78-21capacitors K78-21

DriverDriver Driver is based on the Driver is based on the

Altera programmable Altera programmable logical integral circuitlogical integral circuit

Driving algorithm is Driving algorithm is performed with the IGBT performed with the IGBT current measurement by current measurement by the ferrite current the ferrite current transformers. The transformers. The developed algorithm developed algorithm provides the inverter’s provides the inverter’s IGBT turning-on/turning-IGBT turning-on/turning-off at the minimal off at the minimal current value (zero-current value (zero-current commutation)current commutation)

50 kV, 40 kW step-up 50 kV, 40 kW step-up transformertransformer

The transformer is done The transformer is done with the use of the cores with the use of the cores made from the 5BDSR made from the 5BDSR alloy (AMZ, Russia)alloy (AMZ, Russia)

The transformer is The transformer is equipped with the equipped with the rectifying circuit made rectifying circuit made with the BYX90G (Philips) with the BYX90G (Philips) diodes diodes

The transformer will be The transformer will be arranged in the oil tank arranged in the oil tank which has the following which has the following dimensions: diameter – dimensions: diameter – 480 mm, height – 230 mm480 mm, height – 230 mm

5BDSR alloy5BDSR alloy At the transformer At the transformer

rated duty the rated duty the amplitude magnetic amplitude magnetic inductance value is inductance value is expected to be 0.15 expected to be 0.15 T at the maximal T at the maximal voltage frequency voltage frequency 30 kHz.30 kHz.

Outer diameter of Outer diameter of the cores is 330 the cores is 330 mm, the inner is mm, the inner is 190 mm, the core 190 mm, the core width is 25 mm. width is 25 mm.

The transformer The transformer comprises two such comprises two such the coresthe cores

PowerPowerlosseslosses

Voltage frequencyVoltage frequency

MagneMagnetic tic inductiinductionon

20 kHz20 kHz 30 kHz30 kHz

0.15 T0.15 T 13.5 W/kg 13.5 W/kg (24 W/kg for (24 W/kg for 50NP)50NP)

0.2 T0.2 T 13.5 W/kg 13.5 W/kg (25 W/kg for (25 W/kg for 50NP)50NP)

Electrical strength along Electrical strength along the solid dielectric surfacethe solid dielectric surface

In the quiet homogeneous In the quiet homogeneous electrical field (E) the electrical field (E) the electrical strength along the electrical strength along the solid isolator surface is solid isolator surface is comparable with the comparable with the electrical strength through electrical strength through the main dielectric body (oil)the main dielectric body (oil)

There is no the isolator There is no the isolator surface extension. The surface extension. The isolator height is equal to the isolator height is equal to the oil isolation gap height (h)oil isolation gap height (h)

At the windings ends where At the windings ends where the electrical field is strong the electrical field is strong heterogeneous the pure oil heterogeneous the pure oil isolation is providedisolation is provided

ConclusionConclusion The half-bridge inverter PS prototype test The half-bridge inverter PS prototype test

results proved the operation ability of the results proved the operation ability of the PS power scheme and the control schemePS power scheme and the control scheme

It allowed to make precise requirements It allowed to make precise requirements to the next high-power PSto the next high-power PS

Today the work on the PS launching on Today the work on the PS launching on the VEPP-5 modulator is carried on. The the VEPP-5 modulator is carried on. The next power supply is to provide the 40 next power supply is to provide the 40 kW output power at the voltage 50 kVkW output power at the voltage 50 kV