This invention relates to a double-rotating electric machine which may act either as a (flywheel)-starter-motor, as a generator and/or as a different¬ ial torque-converter. The invention moreover relates to the various practi¬ cal forms, matching control-devices and auxiliaries which enable the machine to be used in a number of different applications.

The machine consists of an inner-rotor and a, preferably weighted, outer- rotor of which either one may be connected, directly or by means of a gear¬ wheel or flange, with an incoming or outgoing shaft, whereby moreover said rotors are connected with two elements of a planetary-gear while the third element of said gear is connected with a second incoming or outgoing shaft. Both rotors may rotate in the same direction, or opposite to one another and one of the rotors may be blocked, giving said machine a fixed transmission-ratio which is independent of an eventual electric load. An important characteristic of the machine is the fact that it may act as a starter-motor for internal-combustion-engines (called i.e.engines or engines hereafter) in more than one way, enabling the storage of kinetic energy in the outer-rotor in order to use the machine as a flywheel starter-motor. The double-rotating machine can be used either as an electric motor/generator or as a flywheel-starter-motor. For the latter, one of the elements of the planetary-gear may be temporarily blocked, either connected to a stationary point or, directly or indirectly, with one of the remaining elements of said planetary gear. As its differential action is determined by the electric load the machine is suitable to act as a differential torque-converter. Such converters consists of two parallel transmissions one being mechanical, the other hydraulic or electric. As compared with other constant variable transmissions, said torque-converter has the advantage of a high power-density and lower losses as only part of the energy is transmitted electrically or hydraulically while the remaining part of the energy is transmitted by the gearing. In common practice said gearing is a planetary-gear of which two elements form the ingoing and outgoing element respectively and the third element is connected with a generator. Said generator is part of the parallel transmission feeding a motor connected with the output. Regulating the load of said generator determines the slip in the planetary-gear and so the transmission-ratio.

Electric differential torque-converters have the advantage here of easy and precise control but have, especially at high power, the drawback of low power density and critical construction as compared with the hydraulic counterpart. The latter is partly due to the fact that in common practice, the electric motor and generator are situated next to the main-axis and, especially with low speed applications, additional gears are required to obtain speeds, practical for electric machines.

The Electric-Differential-Torque-Converter ( called E.D.T.C. hereafter) in this proposal makes use of a double-rotating electric machine whereby either inner-rotor or outer-rotor also forms operative part of the mechanical transmission and whereby, to obtain maximum constructive stability, the planetary-gear is preferably mounted in the outer-rotor.

U.S. patent .260.919 describes a similar double-rotating generator however, as inseparable constructed part of an electric transmission of which both motor and generator are double-rotating. This construction is unnecessary complicated for most applications because the ingoing shaf goes through the first inner-rotor; two planetary gears are being used, both being situated between generator and motor. As the outgoing shaft is thus formed by the inner-rotor shaft, this results in a very heavy construction for low-speed applications and a special construction for the inner-rotor shaft of the generator. The proposed adaption of the generator to low-speed engines implies that all energy should be converted electrically as the proposal offers no parallel transmission. Unlike the machine in present proposal the machine in question is unsuitable for a double-function as flywheel-starter-motor for i.e.engines.

In order to obtain double-rotating action for the generator proposed here, three different gear-arrangements may be used which are depicted in fig.l. The three elements of the planetary-gear may be connected as follows:

Fig.la: Input-shaft with planet-carrier, outer-rotor with ring-wheel, inner-rotor with sun-wheel.

Fig.lb: Input-shaft with sunwheel, outer-rotor with ring-wheel, inner-rotor with planet-carrier. Fig.lc: Input-shaft with ring-wheel, outer-rotor with planet-carrier, inner-rotor with sunwheel.

In principle all three versions have similar characteristics and have in

common, that the output-shaft may be connected with the outer-rotors instead of the inner-rotors, and that input and output may be reversed. With the same gear-ratio the versions differ mainly in effective generator- speed and input and/or output-characteristics. Due to this similarity between the versions, this proposal will be limited to Fig.2 in as far as explanation of the working principles of the machine is concerned. Fig.2 shows shaft 201, connected with inner-rotor 202 which in turn is connected with sun-wheel 203 of the planetary gear. Said gear is mounted in the outer-rotor 20 in such a manner that ring-wheel 205 is fixed, in or at said outer-rotor. Planet-carrier 206 is indirectly connected here with the output-shaft 207- Slip-rings 208 are mounted at the outside of the outer- rotor and the machine is surrounded by a housing 209 with bearings 210 and brushes 211.

The machine has a friction-disk 212 in order to use the machine as a flywheel-starter-motor. Therefore, three of the elements of the planetary- gear are connected at the outside with three elements of a double- concentric brake-disk 213, which elements may or may not have a double- function as parts of a bearing or sealing. Furthermore the outer sides of elements 21 and 215 ma be covered with a suitable friction-material. Element 216 is slightly recessed and functions as second planet-carrier. Said element is connected by means of three or more small shafts 217, preferably those on which the planet-wheels are mounted, with the brake- disk 212 in such a way, that said disk may slide back and forth over said shafts. Coil-springs 218 are mounted around said shafts. At its back-side, brake-disk 212 is rotatable connected with the threaded shaft 219 of servo-motor 220. At the back-side of disk 212 a second brake- disk 221 is connected with housing 209. A round hole in disk 221 permits shaft 219 to pass through. Servo-motor, preferably a disk-motor type, may be connected with disk 221 or housing 209- Furthermore for the torque-converter version shaft 219 is hollow in order that shaft 207 may pass. Shaft 207 is connected with a splined bush with spring 222 at disk 212 in such a way that said disk may slide but not rotate in respect to said shaft. The motor is preferably of the brushless type with permanent magnets fed by an inverter. As a flywheel-starter-motor, the inner-rotor-driven version works as fol¬ lows: Once connected with the engine-flywheel, (which connection in most cases may be permanent, ) electric power is fed to the machine. Due to the

high torque of the i.e.engine the inner-rotor instead of the outer-rotor will rotate as the planet-carrier is temporarily running free, the brake- disk 212 being pushed in its neutral position by servo-motor 220. The outer-rotor will now speed up , whereby the load-curve, desired and/or maximum allowable speed, is electronically controlled, preferably by a micro-processor.

The machine is hereby electrically fed in such a way, that the outer-rotor runs the same direction as during a direct start the inner-rotor. Should at a given speed the machine be sufficiently loaded as a generator, the resulting torque will drive the inner-rotor and so the engine-flywheel, and start the engine.

Said generator-torque can be accomplished, depending on the machine to be used, i.e. by connecting a diode between appropriate armature-windings, or by short-cutting said armature, or by using a direct-current, connected to the aπnature. Preferably however a circuit is used (either built-in or not,) using thyristors or FET-transistors, regulating by means of phase- control said short-cut or mutual connection of armature-windings. The resulting starting torque is moreover enhanced here, by a controllable mechanical coupling situated between inner-rotor and outer-rotor. To acco - plish this, a friction-disk 212 is pushed to disk 213 by the servo-motor 220. As a result of both actions the planetary-gear virtually "stiffens" and forms a third parallel-path. Alternatively after reaching the desired speed of the flywheel, the machine may be fed electrically in reverse at full power, forcing the outer-rotor back-wards. The machine may start directly, or by locking the outer-rotor with the outer-casing or, by pushing friction-disk 212 to disk 221. In the latter case both rotors run in opposite direction which results in a virtual built-in reduction with high torque. With the flywheel running backwards a second flywheel starter mode is also possible here by delaying the connection between said disks. Again, electric current may continue, this time without the necessity to reverse polarity.

In an outer-rotor-driven version of the machine it is clear that it's impossible to use the outer-rotor as an independent flywheel-mass. In this case a flywheel may be connected with the inner-rotor shaft. As a flywheel-starter-motor the E.D.T.C. is very well suited for use with Diesel-engines. Especially at low ambient temperatures these engines demand very heavy starter-motors and big batteries in order to compensate the

combined effects of reduced battery-capacity, low oil-temperature and lower compression-end-temperatures associated with freezing conditions. By storing kinetic energy, discharging the battery with relative low currents over a longer period, the E.D.T.C. is able to start the i.e.engine immediately. The advantages are clear: Installed battery-capacity may be be minimal and is applied much more favourably, while peak-currents are reduced. The latter is especially important with semi-conductor controlled machines i.e. permanent- magnet machines. A microprocessor may completely automate starting-procedures and at choice starting-mode, start-time and battery-conditions can be displayed.

Preferably the starting procedure will be as follows: Primarily the engine is started in a direct mode but this attempt may be aborted directly or after some revolutions, due to the simultaneously monitored engine-tempera¬ ture and battery-condition. The latter causes the internal resistance of the battery to increase if its condition decreases, which comes to expression as a resulting voltage-drop once the battery is heavily loaded, i.e. during this direct-start-mode. As a result of this monitoring, the controller decides either to continue a direct-start or to abort and prepare a flywheel-start and in the latter case to determine parameters like load- c.q. discharge-curve, minimal flywheel-speed, time for eventual glow-plugs to be switched on etc. In this way it is possible to start piston-engines even at extreme cold conditions with a net-torque which would normally not even be available at optimum conditions. In order to use the machine of Fig.2 as a E.D.T.C. after starting, the planet-carrier has to be connected, direct or indirect, with an outgoing shaft. Torque-conversion may now be realised in several ways: *1: The generator is connected via the .outgoing shaft directly with a load and a slip between in- and out-going shafts is determined by the electric load of the generator. Said load may consist of a dissipation of generator- power, internally or externally, or both if after the eventual short-cut thyristor a series-diode is used. An external load of the generator may then consist of feeding control-circuitry, batteries, electric motors etc. Generator-slip determines outgoing speed and may be precisely determined if a tacho-sensor on the outgoing shaft helps form part of the control- circuitry. .

Fig.3 shows a E.D.T.C. primarily meant for turbo-compounded piston-engines to which end shaft 307 is connected with the sun-wheel and the inner-rotor

with the planet-carrier. Friction-disk 31 is connected with the outer- rotor preferably via little shafts in a way similar to Fig 2. Shaft 307 passes disk 32 and is not connected with same. Moreover the shaft connected with the inner-rotor is normally permanently connected at the other side with the engine at choice directly to its flywheel or not. To act as a flywheel-starter, shaft 306 preferably includes a fluid- or electric-coupling 32 . The construction is meant to provide for a fast shaft on which, except an exhaust-gas turbine, preferably one or more compressors are mounted, which may or may not be of the turbine-type. Eventually an extra gearing may be built in the outer-casing to adapt the generator to very fast shafts.

Generator-control may now regulate compressor-speed by, depending on turbi¬ ne-power, transferring part of said power to the crankshaft or, by switching to motor-mode, increase compressor-speed. Action as starter is similar to Fig.2 except that for a flywheel-start the sun-wheel has to be disengaged from the turbine-shaft in most cases. Should a fluid-coupling be used for this purpose it's fluid-circuitry preferably should form part of the engines oil-circuitry and said coupling should be emptied when stationary. As friction-disk 31 is coupled with the outer-rotor, the latter may be connected with the outer casing making a single-rotating machine, i.e. for a direct-start or for situations where compressor- or generator-demand is higher than the turbine can deliver. This may easily be the case when prolonged low-speed and/or low-power use of the engine, prevents the use of the battery to increase turbo-shaft-speed. With a suitable gear-ratio between engine and generator, compressor-yield may be considerably increased at low i.c.engine-speed using this direct crankshaft coupling especially so, if a non-turbine type of compressor should be used i.e. of the Wankel-type.

A complete external dissipation of electric E.D.T.C.-power may consist of powering electric-motors driving auxiliary power-tools and/or, in case of vehicles, extra wheels. In latter case, for practical use of such a type of torque-conversion (electric-motors indirectly help to drive the load here) one might think of applications like railroad-traction, self-propelling welding generators, cranes etc. Fig. shows the principles of such an application. A double E.D.T.C. is used here to drive two or more wheels independently. For this, the machines preferably are built inside the

crankcase of the driving piston-engine, resulting in a compact and very stiff crankcase with cooling and lubrication of the machines made easy. Both electric-machines preferably have a common outer-rotor, driven via one or two gear-rings around said rotor and their outgoing shafts independently drive one (pair of) wheel(s) each, whether or not via extra gears.

The E.D.T.C. 's preferably feed two or more electric motors driving the remaining wheels of the vehicle and/or, in case of a hybrid-concept, charge drive-batteries to prepare for an all-electric drive. For said concept the E.D.T.C. may be used as battery-fed electric motors in which case preferably the i.e.engine should be blocked. This construction is very suitable moreover for mobile workshops etc. delivering full electric-power when outgoing shafts are blocked and, as each driven wheel may be electronically controlled, such a vehicle is exceptionally suited for off- road conditions. As both generators and eventual extra wheel-motors may be loaded differently, power-steering, Anti-Blocking-System and Track-Control on all driven wheels are thus logical integrated options. Flywheel-storage i.e. for brake-energy can't be realised with the E.D.T.C. 's of Fig.4, and with Fig.2 only properly so, if the outgoing shaft 207 is in some way disengaged once the flywheel reaches its, for the situation, maximum speed. Disengaging may take place in several ways i.e. with a clutch or by completely pulling the shaft out of bus 222. Therefore bus 222 may be connected with disk 212 via a in-between shaft and placed behind the servo-motor or outside the outer-casing entirely. Fig.5 shows this solution which is in fact a simplified version of Fig.2. For driving a vehicle the E.D.T.C. may be placed in line with the driving i.e.engine and, directly or not, drive a propeller-shaft or, an eventually transverse-placed, i.e.engine may drive two of these E.D.T.C. 's, each driving (one pair of) separate wheels. For high-power use as E.D.T.C. the flywheel 530 of Fig. normally won't be used. For a flywheel-start of a piston-engine . such big flywheels demand to much power to be invested and the logical option of storing brake-energy has the same limitations as Fig.2, and leaves out the till then driven wheels for this type of braking. This may be solved by an arrangement where machines of Fig.5 are used as wheel-motors being fed by E.D.T.C.(s). Out-going shaft 507 may now be dispensed of but the flywheel should be installed. This wheel-motor serve as Flywheel-Motor-Generator (to be called F.M.G. hereafter) and are, directly or not, connected with wheels not driven by the E.D.T.C. 's.

This arrangement works as follows: The F.M.G. receives electric energy from the E.D.T.C. forcing the outer-rotor backwards and the inner-rotor in the driving-direction of the vehicle. Friction-disk 512 of the F.M.G. , operated by the, preferably electric, servo-system 520 keeps during normal drive conditions planet-carrier 506 connected with stationairy friction-disk 521. To store brake-energy, outer-rotor 504 is at first connected with inner- rotor 502 till they synchronise after which the friction-disk is placed in neutral position and the F.M.G. is fed in reversed polarity by the E.D.T.C. increasing flywheel speed while forcing the inner-rotor to run backwards, braking the wheels. Once the vehicle accelerates again, friction-disk 512 may be connected either to the outer-rotor or to the stationary-disk resulting in a forward or backward movement of the vehicle. The outer-rotor may moreover be supplied with a, preferably tacho-sensor-controlled, block¬ ing device for single-rotating use, during which the friction-disk should be in neutral position of course. The flywheel may be used to store energy whilst stationary, be it from the i.e.engine or from the batteries to supply burst-energy i.e. to start the i.e.engine or to increase acceleration after standstill. As this kind of wheel-motors preferably will be used at the rear of the vehicle because of the kinetic behaviour of flywheels, eventually the almost ideal control-ability of electric machines may be used to obtain an extra pair of steered wheels by loading opposite wheel-motors independently. Therefore shaft 501 is connected, preferably via (some kind of) a universal-joint, with wheel-shaft 54l, which in turn is connected with a double-working hydraulic cylinder 542, which cylinder is connected by hydraulic pipes 54 with the cylinder of the opposite wheel. An unequal motor- or generator-load now results in a simultaneous and coordinated wheel-deflection of both wheels which is dampened by said cylinders. Electric displacement-sensors in combination with one, preferably electrically operated, valve or gear-pump may now easily coordinate, control and/or block this movement.

Windmills are another application of the E.D.T.C. The outgoing-shaft may either be blocked or connected with a load i.e. a pump. The yield of said pump may now be regulated mechanically and may be maximum (inner-rotor and outer-rotor blocked) or zero (outgoing-shaft blocked) as well as regulated electrically. When connected with the mains, pump-yield may be regulated

over the entire range and the E.D.T.C. moreover may then be used to drive the pump when the windmill is at standstill. For autonomous wind-diesel- systems the outgoing-shaft may be connected with the i.e.engine and start said engine when necessary. An eventual load may now be connected in series (between diesel and E.D.T.C.) or parallel with the engine, in both cases electric-magnetic clutches may be used to control the different configura¬ tions.

A similar use for the E.D.T.C. is with no-break-sets or total-energy-sets. Application is especially interesting here when electric power is primarily meant to feed electric motors. The E.D.T.C. may replace such motor's and may be fed from the mains when the i.e.engine is at standstill. Stored flywheel-energy may be used to start the engine and an inverter may be used for variable load-speed when powered from the mains. Said inverter doubles as frequency-converter once the i.e.engine is started, feeding back into the mains or replace it. Off-mains, load-speed may still be regulated by internal dissipation up to maximum load, however, minimum-load-speed is determined by external dissipation unless the outgoing-shaft is blocked. The inverter preferably should have a D.C. stage and the load preferably should have extra flywheel-mass.

*2: E.D.T.C. in line with a electric motor, in which case outgoing-shaft from the first machine directly is connected with the ingoing-shaft from the second machine, using one of the configurations of Fig. 6. The second machine in turn may directly or via a planetary-gear be connected with an outgoing-shaft to drive a load. In case a reversing-gear should be needed, it should preferably be electrically operated and preferably should be placed between first and second machine. The second machine may be a conventional machine or a flywheel-version of the E.D.T.C. The latter is especially useful if high burst-energy should be applied to a load. In normal use the outer-rotor of the second machine could be blocked.

A transmission as depicted in Fig. 6c with outgoing planetary-gear is especially suitable to replace diesel-electric-drives with slow-speed i.e.engines i.e. for ships. As, compared to a direct driven propeller- shaft, the biggest part of the shaft is much faster and, as it works in part-load here, shaft and eventual reversing clutch and couplings may be considerably lighter. *3- E.D.T.C. in line with a second electric generator: In principle similar

mechanical configurations are possible according to Fig. 6 as described in *2. Also here, the second generator may have an outgoing-shaft to drive a load. Application of such double-generators is especially interesting in cases where two different sorts of output are needed, i.e. a low-voltage D.C. and a high-voltage A.C. A.C.-frequency-control and/or mutual balancing loads may be accomplished in different ways preferably here however, by changing the load of one of the generators using a inverter to shift electric power from one generator to the other. One application of Fig. 6c, in most cases however without second planetary-gear, is for aircraft, where stored flywheel energy may be used for starting.

Installed flywheel-capacity with the versions of Fig. 6 play an important role in applications like total-energy, no-break-sets etc. as a very fast engine-start is guaranteed here as long as the flywheel is running. Therefore the flywheel-generator may be fed from i.e. battery-chargers or directly from the mains. With sufficient flywheel-capacity a major drawback of most emergency power-systems, may thus be overcome: the primary use of costly batteries and inverters to close the gap between a power-failure and start-up of the no-break set. Installed extra-flywheel capacity on the rotor shaft of the second generator and/or the use of a weighted outer- rotor in case of an inverted machine may be an extra help to stabilise its frequency against fast load-changes.

A logical reason to keep the generator stand-by is described under *1: the driving of a load. As the unit is now fed from the mains during stand-by, preferably via the E.D.T.C. and using a inverter if so needed, the second synchronous generator may be used in a double-function as line-conditioner. Said devices are frequently used to protect computers against all kind of problems stemming from a "polluted" mains. In such a double-function the generator-unit acts as rotating converter during stand-by. Also, the generator-unit may have the configuration of Fig. 6c and may have a outgoing-shaft with or without planetary-gear to drive a load. It is clear that load-speed can't be variable in case of the application just mentioned. The outgoing-shaft however, may have a electric-magnetic clutch to discontinue load-drive. This may be important to preserve flywheel- energy for starting and the continued delivery of electric power. Using units from Fig. 6a or 6b, an alternative to this concept permits within certain limits the change of as well electric load, mechanical load and load-speed while the frequency of the second generator remains stable. For

this, E.D.T.C. 601 is fed from the mains using a inverter of which its control-parameters are determined by the electric load of E.D.T.C. 602 as well as the mechanical load and desired speed of the outgoing-shaft. E.D.T.C. 601 preferably is a synchronous type electric machine with permanent-magnets and the inverter^ is preferably pulse-width modulated with a D.C.stage. Motor/generator drives generator 602 which is electrically loaded by the "computer-grid" and of which the outgoing-shaft is connected with the load. In case permanent-magnets are used for generator 602 said generator is designed to deliver just over mains-voltage at mains- frequency. It may be clear that, as the effective-speed of generator 602 should result in a constant frequency of i.e. 50 hz, the speed of its outgoing-shaft is exclusively determined by the speed of the ingoing-shaft- of generator 602 to which however the electric load of generator 602 should be adapted. Speed of the outgoing-shaft may now be varied till, electrically, full-load is reached for generator 602, downwards however, variation is limited by the electric load of the "computer-grid" fed by generator 602. In this case instead of disengaging, here the outgoing-shaft might eventual be blocked if needed. An upwards variable electric load is realised also here by load shifting, in this case either by feeding after rectifying into the D.C.-stage of the inverter, or by feeding directly back into the mains. The latter however, implies a risk of introducing mains- pollution.

Off-mains starting is as described before, however, behaviour and so the control of generator 602 is mainly determined by the mechanical load. If needed extra flywheel-mass may be used on the outgoing-shaft to said load. As high power densities may be achieved with this type of generators, oil- cooling may be considered, combining its advantage with the need for lubrication of bearings and gears. If driven by an i.e.engine said oil- cooling could be integrated with the oil-circuit of said engine. In such a case inverse-built machines and/or slip-rings on either the inner-rotor- shaft or on the bearing-bracket of the outer-rotor are to be considered.

The next part of this proposal is related to brushless double-generators with their auxiliaries and control-devices. To eliminate brushes, the rotor of a single-rotating electric machine, whether or not built inverse, is connected with one of the E.D.T.C. 's of Fig. 1 via the armature-rotor of said E.D.T.C. , be it the inner- or the outer-rotor, of said E.D.T.C. In

contrast to E.D.T.C. 's described before, speed-control is accomplished here, using a wireless-controlled, built-in, regulating-circuit, directly or indirectly mechanically connected with said armature-rotor, regulating internal dissipation by either, in part, short-cutting the entire armature, or by connecting appropriate armature-windings with one-another, in both cases preferably using phase-control. Moreover, if said single-rotating electric machine uses field-windings, said windings are on the driven rotor of said machine and receive their power of the armature of said E.D.T.C. via the aforementioned regulating-circuit. As preferably a brushless- machine-type is used for the E.D.T.C. thus brushes are avoided on both machines, eliminating a draw-back of the machines described so far. This makes sense especially for application in aero-space where, besides more general considerations on maintenance and reliability, brittleness and bad conductivity of brushes, both due to low air-humidity on high altitude, play an important role in generator-design.

Wireless-control of the regulating-circuit may be of any type, preferably however using inductive- or optic-sensors. For flywheel-starter/generators common outer-rotors are preferable, using existing machine-mass for flywheel and simplifying mechanical design.

This design is shown in Fig. ^~ , which may be used as flywheel-star¬ ter/generator for aircraft where the E.D.T.C. 701 drives the inverse synchronous-machine 702 via their common outer-rotor 703. said outer-rotor respectively containing the armature of 701, the regulating-circuit 720 and the fields of machine 702. The inner-rotor of 702 preferably uses permanent-magnets and is connected with the planet-carrier 705 via a hollow shaft while the ingoing-shaft 706 is connected with sun-wheel 707. ring- wheel 708 is connected with outer-rotor 703. The outer-rotor 703 may be weighted for extra flywheel-mass and is rotatable via bearings on bearing- brackets 709 and 710 around fixed shaft 711. The armature 712 of machine 702 is connected with said fixed shaft around which moreover rotor 704 rotates using bearings 717. Shaft 711 passes planet-carrier 705 and hollow shaft 7θ6 on its way outside and may be connected with the casing. As a generator the unit of Fig. ^~ J works as follows: The E.D.T.C. is driven by the auxiliary-shaft of the i.e.engine via gear-wheel 716 on shaft 706, which shaft drives sun-wheel 707- As a result of this, planet-carrier 70 and so inner-rotor 704 rotate. An electric torque between said inner-rotor

704 and armature 713 on outer-rotor 703 forces the latter to rotate as well and virtually "stiffens" the planetary-gear proportional to said torque. As a result of this, two parallel transmissions are created, resulting in a relatively low electric dissipation of the E.D.T.C. in relation to the output. Dissipation of the electrical output of the E.D.T.C. is controlled and effected partly outside, (control-unit) partly inside the generator (power-unit) , the latter preferably using thyristors or FET-transistors for phase-control, after which the remaining part of the sinus is used for exitation of the field 715 of generator 702. To prepare for a flywheel-start, the unit may be fed by a relative simple square-wave inverter of which the frequency may either have a fixed curve in time, or may be tacho-sensor-controlled. Once the desired flywheel-speed is reached, the E.D.T.C. may be loaded starting the i.e.engine. As primarily field 71 is hardly exitated by the E.D.T.C. during starting, two alternatives may be considered to improve start-up:

1 Current induced by the armature into the field may be short-cut single- sided by either thyristors or FET-transistors preferably using phase- control to build up a D.C.field.

2 An electric current may be fed directly to the (side of) the outer-rotor using a system of slip-rings 719 and retractable brushes 718, whereby said brushes may be controlled by a solenoid or servo-motor which retract the brushes once the E.D.T.C. takes over excitation. A similar construction may also be applied when the use of the E.D.T.C. is preferred for start-up of the flywheel. This may considered for starting from batteries in which case the E.D.T.C. working-voltage may be low compared to generator 702. In general however, working-voltage of the E.D.T.C. should be as high as possible in this application in order to minimise semiconductor losses. The capacity of the unit to supply burst-energy for starting is determined mainly by the power-rating of the E.D.T.C. As especially which aircraft weight and size are important factors, said rating preferably will be kept to the minimum required for generator-control. Peak-capacity for starting may be drastically increased however, by using a friction-disk, either directly between flywheel and outgoing-shaft or between flywheel and one of the remaining elements of the planetary-gear as discussed previously in relation to Fig. 2 and 5-

An alternative construction for a friction-clutch uses the lateral-force of helical gears, alongside or instead of, a servo-system, to apply the

necessary force on the friction-disk. As the direction of said force depends on rotational direction and on whether the gear-wheel in question is driving or being driven, the magnitude of said force is determined by the teeth-angle and the driving-force. As generally rotational direction with starter/generators remains fixed, only the condition whether said machine is driving or being driven, determines now if a friction-clutch is engaged or not. The gear-wheels in question may be part of the planetary- gear and the friction-disk may be inside the machine, whether or not using the bearing-bracket for counter-disk. If such an internal friction-disk should be used in the machine of Fig. 7. preferably said friction-disk should be connected with the planet-carrier. Said friction-disk preferably should be slightly conical, made out of steel and be surrounded by a ring- shaped permanent-magnet to collect steel-particles thrown outwards by centrifugal force. Moreover the friction-disk should preferably be thermally isolated from the planet-carrier and preferably a spring should be used between both disks. As the lateral-force on the friction-disk of the mechanism described here, has in principle the character of an avalanche-effect, of which the forces involved are mainly limited by the physical properties of the friction-disk, in this case the electric-torque between inner-rotor and outer-rotor plays an important role. Although primarily torque is affected between the planet-wheels and the ring-wheel by the friction-disk, shunting inner-rotor and outer-rotor, the resulting torque finally affects torque of the planet-wheels versus the sun-wheel and it is this latter force, counteracting the lateral-force between ring-wheel and planet-wheels, which finally determines the lateral direction of the friction-disk. However, once generator-torque of the E.D.T.C. decreases, the lateral-forces between ring-wheel and planet-wheels get the upper hand, counteracting the lateral-force on the friction-disk until finally said friction-disk is disengaged. This same principles may be applied in respect to Fig. la and lc to control the action of a friction-clutch between elements of the planetary-gear. In such a case, either sun-wheel or ring- wheel may be used instead of the planet-carrier for axial movement of the friction-disk. As an alternative to using the planetary-gear, said type of friction-disk ^~~~ - ^~ ~y be placed outside the machine, eventually using one single gear-wheel, i.e. gear-wheel 716 to play a similar role. Said device is depicted in Fig. 8 and uses a hollow shaft 823 to which helical gear 816 is connected,

whereby said gear-wheel is engaged with gear-wheel 822. Hollow shaft 823 is connected with the outgoing-shaft of the machine via splines, allowing an axial movement in respect to said outgoing-shaft and at the machine-side of shaft 823, friction-disk 820 is connected with said shaft. Preferably a spring 824 is used between disk 820 and the counter-disk, whereas said counter-disk may or may not be (part of) the bearing-bracket of the machine involved. For other applications i.e. some machines described previously, a second disk 821 and spring may be used i.e. for blocking the shaft. Basic principles are similar as described before and, depending on the rest of the design, at wish a double-action friction-disk is thus realised which may have, using the springs, a neutral position that may eventual be locked i.e. by a solenoid.

Especially £©x- the combination of this kind of friction-clutch with Fig. 7 results in a relative light and efficient starter/generator as compared to the conventional combination of pneumatic starter, hydraulic constant- speed-drive and generator , allowing for a very fast start-up of the gas turbine. The total amount of energy to be stored in the flywheel, (and so its weight, ) may be moreover reduced by continued delivery of electric power to generator 702 during the whole start-up procedure of the gas turbine. In such a case the inverter preferably should be controlled by a tacho-sensor on generator 702 to adapt its frequency to said machine. For reasons of price, weight and simplicity, preferably permanent-magnets will be used for the fields of the main-generator in all those cases where either A.C.-voltage-control is not necessary, .or A.C. will be rectified to D.C. as is mostly the case in vehicles. In latter case voltage-control can simply be obtained by speed-control of the main-generator.

Compared with conventional starters for operation with piston-engines, a relatively low gear-ratio to the i.e.engine-flywheel is necessary. This however poses no problem as units like Fig. 7 are not suited for a direct- start and at all times flywheel-action of the outer-rotor will be used to increase the torque. Depending on i.e.engine temperature and battery- condition, more or less energy will be invested into the outer-rotor whose flywheel-action during starting surpasses same of the i.e.engine-flywheel at around 2000 - 3000 r.p.m. in most cases. This speed will be reached in a fraction of a second under normal battery-conditions, after which, with normal i.e.engine-temperature, the E.D.T.C. may be loaded while flywheel- speed is sustained by feeding the main-generator. As an alternative to this

"direct-start"-mode, more energy may have to be invested in the flywheel before the E.D.T.C. is loaded and the main-generator may be switched-off once the desired flywheel-speed is reached, only using flywheel-energy to actually start the i.e.engine. It may be clear that depending on the application, for a E.D.T.C. as well as for eventual electric machines driven by the E.D.T.C. , different type of electric machines may be used. Logical choice for D.C.-operated (starter- )machines seems the use of collector-machines. However, conventional designs will have some serious drawbacks in respect to brush- wear, field-exitation and maintenance when combined with an outer-rotor. To overcome this, a D.C.-machine may be inverse-built allowing the collector to be connected with the outer-rotor, or the armature-windings may be connected with the bearing-bracket allowing the collector to be built any place on or around said bearing-bracket. For critical applications like aircraft, brushless machines remain to be preferred, however it is clear that without further measures such machines cannot be used for D.C.starter. Unfortunately the use of inverters unless in a double-function is costly and has some disadvantages if low (battery- )voltages are involved. Even with a flywheel-start, the high currents involved with electric starting, (which are higher with dropping voltage), require costly semiconductors which, as a result of internal resistance has negative effects on conversion-efficiency, will have to be designed for a high internal dissipation. A solution for this may be an electronic-electric-mechanical converter in which the pulses from a pulsating D.C. , generated by one or more semicon¬ ductors, are shunted by a mechanical switch, said switch preferably being of the rotating type, operated by a servo-motor running synchronous with said pulses. Such a switch-device is depicted in Fig. 9. The rotor 901 of this, preferably vertical placed, servo-motor 902, uses homopolair permanent-magnetic poles which come together at one side to form one ring- shaped homopolair counter-pole 903- This counter-pole serves as part of an electric-magnetic switch which, once an electric-magnet 904 in the armature-part of said machine is exited, lifts the rotor. By this vertical movement the main-switch of the device is closed. An isolated disk 906 is connected with the shaft 909 of said rotor, which shaft preferably doubles as part of said main-switch and is therefore made from a electrically conducting metal and isolated from said rotor and the housing of said

motor. By said vertical movement, said disk, into which switch-contact- segments are embedded preferably connected with said rotor-shaft, is placed into (closer) contact with brushes 908, said brushes being connected with the housing of the device. For the servo-motor control preferably power MOS- or HEX-FET's are used while said semiconductors) simultaneously deliver(s) the flanking parts of the final power-pulses. Therefore, said the semiconductor(s) are saturated by positive or negative sinus-halves from a preceding oscillator or from a pre-amplifier stage amplifying the tacho-sensor signals from the electric motor to be controlled. Said saturation results in a steep slope of said sinus-flanks and a relatively flat top. Said sinus-top's and so the preceding semiconductor power-stage, are now shunted by the contact-segments of said switch. As a result of this, 90 % or more of the final electric power is handled by the switch, resulting in low semiconductor-losses at one hand, and only small "voltage- jumps", minimising sparks and in-burning during switching, on the other hand. The same spark-free operation is accomplished for the main-switch of the device as the semiconductor-circuit preferably is not operated by said switch and its power-stage preferably is put into its "firing-state" during a status-change of said switch. Adapted versions of this switched-shunt- converter may be used to generate and handle A.C. instead of pulsating D.C. Especially in combination with small i.e.engines the flywheel of the E.D.T.C. may be used for starting the i.e.engine by hand. For this, the housing of the E.D.T.C. should be designed to allow a cord to be wound around either the flywheel itself, or a flange attached to said flywheel of said E.D.T.C. Therefore eventually said flywheel has to be rotated backwards by hand. Only after said flywheel is speeded-up the E.D.T.C. is loaded whether or not automatically or by a hand-operated switch. For a number of applications described in this paper it may be worthwhile to consider the configuration of Fig. la for E.D.T.C. The advantage here is the higher effective speed of the E.D.T.C. with equal in- or out-going speed. Fig.10 shows the use of such a machine for applications where a high flywheel-storage-capacity is required when at the same time said energy- storing should be controllable to a great extent independent of the output of the main-generator. Therefore both inner-rotors are connected here to one another mechanically, and electrically via the regulating circuit described previously. Applications for this are i.e. generators for wind¬ mills in stand-alone operation, where now a certain amount of wind-burst-

energy may be stored in the propeller as well as the flywheel, or motor- generators which should be able to deliver a high electric output while following a certain frequency-curve. With another input-gear configuration such inner-rotor-coupled machines may i.e. be used for starter-generator for Auxiliary Power Unit in aircraft where they eventual may replace inverter for starting up the flywheels of the main-i.c.engine-starter- generators of Fig. 7-

Machines of Fig. 7 and Fig. 10 whether or not modified for special tasks, whether or not using a E.D.T.C. for main-generator, whether or not with slip-rings and/or an outgoing-shaft on said generator, may moreover be used in industry as a continuous variable transmission, at choice driven by a i.e.engine or powered from the mains, either to level-out mechanical or electrical peak-loads, or to deliver mechanical or electrical burst-energy.