High Power Processing Unit for Stationary Plasma Thruster

Transcription

1 High Power Processing Unit for Stationary Plasma Thruster H. Declercq - T. Scalais Alcatel ETCA s.a. BP 4008 B-6000 CHARLEROI (BELGIUM) Phone : +32/71/ [email protected] IEPC Alcatel ETCA, uner ESA contract since 1996, has esigne, teste an prouce Power Processing Unit (PPU) to supply the first generation of Stationary Plasma Thrusters (SPT) : the Russian SPT-100 from Fakel an the PPS-1350 evelope an qualifie by the SNECMA company. Base on the experience acquire with this first program, Alcatel ETCA has starte the esign an evelopment activities of a new PPU prouct size to rive the 5 kw class thrusters which are at the present time in progress of test or qualification. This new prouct can be easily aapte to ifferent platforms in terms of electrical interfaces : primary input bus, telecomman-telemetry communication interface, The flexibility of the esign allows to buil, quickly with minimum non recurring activities, a PPU perfectly size to rive any type of Hall Effect Thruster in the range from 1 to 10 kw. 1- Introuction Alcatel ETCA has starte its PPU evelopment activities since January 1996 for the French STENTOR program on the basis of a specification built from the efinition of : - the electrical interfaces of the Fakel SPT-100 an Snecma PPS-1350 thrusters, - the thermal, mechanical an electrical interfaces of most European platforms, From 1999, a Qualification Moel is connecte on a SPT-100 thruster in space environment conitions, at Snecma facilities in France, in orer to emonstrate the lifetime corresponing to the use of the plasmic propulsion for the north-south station keeping on a geo-synchronous satellite. At this ate, more than 6000 hours have been reache without any abnormal eviation of the equipment performances. The objective of 7000 hours woul have to be complete before en of Two 1.6kW class PPU flight moels have been elivere to ASPI for the STENTOR satellite which will be launche in Base on this experience, we have starte the esign of a new generation of PPU compatible with the Hall Effect Thrusters of higher power in progress of evelopment or qualification. The present article, after a brief summary of the characteristics of the current prouct, escribes our next PPU generation : the High Power Processing Unit HPPU which will cover a larger range of power up to 10 kw at least. 2- PPU Main functions PPU is constitute by the following moules (see figure 1) : Interface on the Primary input power bus, insures main bus protection, voltage level conversion an galvanic isolation require by the SPT supplies. SPT power supplies, the 4 types of electroes of the Stationary Plasma Thruster (anoe, magnet, heater, ignitor) are supplie accoring to their specific power profile. 1

2 XFC power supplies, PPU supplies the Xenon Flow Controller : opens or closes the xenon valves an controls the ischarge current by the regulation of the xenon flow via the thermothrottle power supply. Sequencer, insures the automatic control an the survey of the thruster operation : start-up, stop, regulate thrust, failure recovery,... TC/TM interface with the satellite communication bus THRUSTER S P A C E C PRIMARY INPUT BUS INPUT LIMITER INVERTERS ANODE V A & I A REGULATOR MAGNET I M REGULATOR ANODE MAGNET R A F T I N TC/TM BUS (N) (R) TC/TM INTERFACE SEQUENCER HEATER I H REGULATOR IGNITOR PULSE REGULATORS HEATERS IGNITORS T E R F PRIMARY INPUT BUS DC/DC CONVERTER I TT REGULATORS THERMO- THROTTLES A C E ON/OFF TC VALVES DRIVERS VALVES XFC Figure 1 : PPU functional block 3- Performances of our current prouct The main characteristics of the 1.6kW class PPU are summarise hereuner. Compatible with Fakel SPT-100 an Snecma PPS-1350 thrusters Maximum Power in the thruster ischarge circuit : 1600 W Inclues SPT an XFC power supplies Can be equippe with or without a switching moule (calle TSU for Thruster Switching Unit) allowing to rive one out of two motors ; this moule is typically use for north-south station keeping application on geo-synchronous satellite Easily aaptable to any regulate input bus in the range of 50V to 100V TC/TM plug-in moule available for MIL-STD an ML16-DS16 communication busses ; possibility to esign other TC/TM moule for any type of platform interface Efficiency : 92 % in nominal operating conitions Reliability figure for PPU with TSU : fits Mass for one PPU with TSU : 10.4 kg Dimensions : For one PPU : 365 x 190 x 180 mm (LxWxH) For one PPU with TSU : 390 x 190 x 180 mm (LxWXH), see figure 2. Fully qualifie accoring to environment specifications of Europeans platforms 2

3 Lifetime test with SPT-100 in space vacuum conitions : more than 4500 hrs reache objective : 7000 hrs before en of 2001 Two flight moels alreay elivere to ASPI for the STENTOR satellite which will be launche at the beginning of 2001 Figure 2 : 1.6kW Class PPU equippe with Thruster Switching Moule 4- High Power Processing Unit - HPPU 4.1. Anoe supply main characteristics The anoe supply shall interface the input power bus with the plasma ischarge circuit. This function is completely functionally isconnecte from the supply of the other electroes. It may be justifie by the fact that the anoe voltage can fall to zero; furthermore, the nominal power aaptation in the range 1 to 10 kw only concerns the anoe supply. The input power bus stanars may be: either 50 V, 100 V regulate bus, expanable up to 120 V bus; intermeiate values shall be accessible, either unregulate bus, whilst this configuration is not the most probable; nevertheless, the ability to operate with unregulate bus is consiere. The anoe supply is characterise by : a voltage regulation a current limitation with a specific shape. as shown at the figure 3. Typically, the nominal anoe voltage is regulate at ± 1%. Higher power motors may have 350 V anoe voltage; this new prouct will take account of the anoe voltage range aaptability up to 700 V, an anoe maximal power up to 10 kw. V anoe V anoe I nominal I limit W I short igure 3 : V I Anoe characteristic I anoe F 3

4 4.2 Main constraints of anoe supply esign Cost an aaptability The esign shall lea to configurations minimising the complexity an consequently the cost. In the same time, the esign must lea to a maximum of flexibility for the aaptation of the PPU both to ifferent anoe voltages an power an input busses stanars. The most critical point is to choose the best power level for the elementary moules, as the final cost is the prouct of the moules number by the elementary moule cost, the cost of an elementary moule growing with its power Efficiency At power levels up to 10 kw (nominal), efficiency has irect an heavy impact on thermal behaviour. Too high issipations coul lea to technical impossibilities an/or rastic cost impacts. Internal PPU implementation an interface of PPU with the satellite platform are in fact irectly concerne by the issipations Mass, volume, foot print surface These have to be minimise but the preceing constraints seem to be of greater importance. 4.3 Anoe supply The anoe supply may be constitute by np branches connecte in parallel; each branch being able to contain ns smarts being connecte in parallel at primary level an in series at seconary level (see figures 4 & 5). This topology allows a great flexibility with regar to the power level, the components stresses an the technological constraints. The output voltage an the output power limit are ajustable by serial telecomman. It is so possible to aapt the anoe voltage epening on the thruster type or the mission phase (orbit raising or attitue control).it allows also to limit the maximum input current to a value lower than the platform capability. Moule 1 ANODE SUPPLY + Input Switch Input Filter Moule n ANODE SUPPLY - u Current Reguation u i Isolation Voltage Reguation Figure 4 : Branch Topology 4

5 Input Switch Moule 1 Moule n n s Seconaries ANODE SUPPLY Current Regulation BRANCH INPUT BUS POWER Input Switch Moule 1 Moule n n s Seconaries Current Regulation BRANCH CS97/153/3 Common Current Set Point u i Voltage Reguation & Isolation Figure 5 : HPPU : Branches in parallel 4.4 Cathoe Power Supplies. The cathoe supplies inclue: - a current source to heat the cathoe an, after local gas ionisation, to sustain the cathoe ignition The high voltage source an the current source are ajustable by serial telecomman. It allows to easily aapt the cathoe supplies to ifferent types of cathoe. - a high voltage source to ignite the cathoe 5

6 4.5 XFC Power Supplies The XFC supplies inclue bi-voltage sources to comman xenon valves an a current source to control the xenon flow rate. The current source is ajustable by serial telecomman. It is use to regulate the anoe current. 4.6 Thruster/Catoe switching (TSU) The TSU is a moule of the PPU. It supports the output connectors to the thruster an XFC, it contains the relays that connect the power supplies outputs to one of the thrusters or to one of the two cathoes of the selecte thruster. 4.7 TM/TC controller The TM/TC controller interfaces with the platform serial bus, the power supplies, the TSU an the analog acquisition circuits. It also insures some automatism as the anoe current regulation, start-up sequence, The telemetries inclue all the output current an voltage of the DC sources an the current consumption on the primary power bus. Customer Program Spacecraft 4.8 Performances The objectives of: low recurring costs, high efficiency versatility are the main riving parameters for the activities of esign an evelopment of the 10kW Class PPU. Base on the characteristics of the 1.6kW PPU alreay qualifie by Alcatel ETCA, the following figures can be taken as realistic objectives: Due to the large power, up to 10 kw, transmitte by the equipment, the efficiency is among the most critical parameter an will be optimise by low-issipation switching techniques, low conuctances losses, Efficiency > 94 % (EOL), nominal target : 95 % Mass < 15 kg in version 10 kw ; mass ~ 10 kg in version 5 kw Reliability figure : 3500 fits 5- Commercial success Inepenently of the two flight moels alreay elivere to the STENTOR program, ALCATEL ETCA has receive orers to eliver some 1.6 kw PPU in flight version for the following commercial programs: Electric propulsion use for Moels Delivery ate ASPI Astra 1K Telecom GEO NSSK 2 FM s 2000 ASPI GE Americom Telecom GEO NSSK 10 FM s 2001 to 2002 ESA -1 Moon mission Main propulsion 1 FM 1 st half 2001 Astrium Intelsat Telecom GEO NSSK 4 FM s 1 st half 2001 Astrium Inmarsat Telecom GEO NSSK 6 FM s 2001 to 2002 Astrium Option Telecom GEO NSSK 2 FM s Conclusions The table in the previous paragraph shows the confience of primes an customers in the experience an the competence of ALCATEL ETCA concerning the PPU equipment use to rive Hall Effect thrusters of the electric propulsion sub-system aboar satellites or spacecrafts. ALCATEL ETCA has acquire a soli experience an a very goo knowlege of the electrical interfaces between thruster an PPU confirme by the success of numerous integration tests with SPT- 100 or PPS-1350 thrusters. So, ALCATEL ETCA is now well in position to continue the evelopment of the new PPU generation which will be able to rive the higher power thruster, in evelopment or qualification, up to 10 kw. 6

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