EPC Medium Power 3G

Status date

Design, development and qualification of the third generation of the Thales Alenia Space ETCA’s Electronic Power Conditioner (EPC) dedicated to supply and control the Travelling Wave Tube (TWT) that constitute the Travelling Wave Tube Amplifier (TWTA) for Repeaters involved in large quantity in the Telecommunication Payloads.

This new generation has to answer to the evolution of the market in terms of new features, high performances and improvement in competitiveness.

It also must be designed in a way that it will be compatible with the large range of TWT and Payload interfaces proposed on the telecom market.

More and more TWTA are involved in the repeater chain of the telecom payloads thanks to their very good performances at high power regarding to the standard Steady State Products.

The TWT products have followed the constant growth of the requested power and channel bandwidth especially for multimedia applications.

A major drawback of this product is its need to be supplied with very high voltage in addition to specific controls and sequencing according to its operating modes.

The EPC answers this challenge by providing power from the Payload Power Bus (PPB) to the TWT electrodes up to 7 000 volts with level of protection and safety required for space vacuum operation over 15 years.

Consequently to these specific features the TWTA significantly contributes in the payload cost and the competitiveness of this product is continuously addressed.

The EPC 3G MP product developed in the frame of this contract also offers the opportunity of significant improvement of the payload power management through the new feature in Power Flexibility. Managed on ground for the optimisation of the Power budget or in flight for rearrangement according to the actual power demand, this new feature is a key element of the future payloads competitiveness.

TWT + CAmp (optional Channel Amplifier) + EPC

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A major issue is the definition of a “standard” EPC product compatible with the very large range of TWT and Satellite Interfaces, from 20 to 150Wrf TWT in various frequency bands from L to Ka and supplied by 28V to 100V Primary Power Buses.

Specific features also addressed:

  • An extension of the A0 control range for improvement of the regulation and implementation of the Power Flexibility,.
  • Increase High Voltage generation up to 7500V,
  • Improve dynamic performances,
  • EPC maximum mass 1 250 gr.

Special attention is given to the product competitiveness by optimisation of the production process, part selection and standardisations.


The EPC 3G MP reinforces the TAS ETCA portfolio with a competitive EPC product focused on the TWTA market whichis in constant growing demand.

It offers solutions for Single TWTA from L to Ka band, from 20 to 165Wrf, compatible with various Primary Power Buses from BNR 22-37V, 28V, 50V up to 100V and with various monitoring options.

Also this new product offers the opportunity for a fine tuning of the TWT RF output Power trough the Flexibility feature, as well as for ground AIT tuning as for in-flight adaptations. This feature makes a wonderful leverage for competitiveness improvement at payload level through the optimization of the real payload power demand.

At the time of completing this contract more than 160 EPC/TWTA 3G have already been manufactured and delivered. Flight experience started in February 2009 and continues with success.

This product also initiates the Dual Flexible LCTWTA 3G and High Power Single 3G products that will complete the TAS ETCA portfolio, taking a large experience in terms of topology, technology and processing from the 3G MP product.

The resulting enlarged Portfolio will push TAS ETCA as a major contributor of EPC produced for space telecom around the world.


The EPC consists in a high efficiency high voltage converter that delivers the various voltages required by the TWT Cathode, Anodes, Helix and up to 5 Collectors. High accuracy and low ripple are key features for the global TWT performances.

The EPC also provides specific functions dedicated to the management of TWT operating constraints such as start-up and shutdown sequences, controls and protections, etc. The internal implementation guarantees the segregation between low voltage (LV) and high voltage modules (HV).

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The EPC is based on a pre-regulator that interface with the PPB, followed by a quasi-resonant push-pull inverter that drives the High Voltage transformer.

The internal EPC auxiliary supply also provides the polarisation of the filament and Anode 1, and the Camp supply. A high accuracy Regulator sets the Helix voltage. It also provides the opportunity of tuning that enables the HV transformer to be less dependant on the TWT real operating point. Consequently it allows reduction in the schedule constraint and improves the production performances by a better standardisation.

The EPC provides the A0 voltage regulator that directly controls the cathode current. Also this parameter is requested to be very accurate and stable in order to meet the TWT RF output power requested performances. The A0 controls are designed to be easily adapted to the constraints of each type of TWT on the actual market.

The A0 driver is also designed for the management of the RF power flexibility through Telecommand. The accessible A0 voltage range allows controlling the TWT saturation power in a range of 3 dB. With this new feature the Repeater Power can manage the TWT saturation power from the maximum up to -3dB without degradation of the efficiency, and this as far on ground operation for the payload tuning as for flight power change using Telecommand.


The EPC 3G MP takes heritage from previous generations that have demonstrated a strong in-flight experience.

Technologies involved into the HV generation have demonstrated their ability to sustain the space environments over the requested life through a rigorous evaluation plan based on ESA-PSS-02-303 rules.

Design & developments are proposed on approval over classic reviews.

3 EQM are manufactured and tested at the limits of the product variants:

  • EQM 1 : 100V PPB – 165Wrf Ku band TWT, 6500V,
  • EQM 2 : 100V PPB – 240Wdc dummy load @ 7500V,
  • EQM 3 : 28V PPB – 240Wdc dummy load @ 7500V.

Campaigns end by 10.000hrs life test.

Current status

The activities engaged in the frame of this contract have been completed by the successful review of the 3 qualification campaigns. EQM1 10 000hrs life test has been successfully completed.

EQM2 & 3 life test campaigns are in progress and are expected to be completed in early 2012.