FR2729018A1 - DEVICE FOR CONTROLLING THE OUTPUT OF AN ALTERNATOR - Google Patents

Abstract

The invention relates to a device for controlling the output of an alternator. This device for controlling the output of an alternator (610) comprises an inductor winding (620), an output winding (615) and a rectifier (630) coupled to loads (670) of a vehicle (625). The winding (620) causes a thermal overload of the alternator linked to an excessive output current when the excitation current is greater than a limit current, for certain rotational speeds of the alternator. Control means (680, 621) are provided to limit the current of the winding (620) at certain speeds to prevent thermal overload of the alternator. Application to motor vehicle alternators

Description

The present invention relates to an electrical system

  motor vehicle and more particularly a device for controlling the alternator output of this vehicle to improve the output performance and protect the components of the alternator vis-à-

screw thermal damage.

  A typical electric vehicle system

  bile comprises a Lundell-type regulated voltage alternator, rotatably coupled to the vehicle engine for applying energy to vehicle electrical loads, including lighting, instrumentation, auxiliary electrical devices, etc. If the capacity of the alternator is sufficient to meet the needs of the loads, the system voltage is set to a desired control voltage, which is greater than the voltage across the battery, by controlling the current sent to the generator. inductor winding, to a value

  sufficient to maintain the desired control voltage.

  This is why, during such a regulation, the alternator feeds the loads, and the state of charge of the battery is preserved. However, if the capacity of the alternator is insufficient to meet the needs of the loads, the battery is solicited to provide the difference, and its state of charge decreases. Such regulation is not possible when the demands of the loads exceed the capacity of the alternator, and therefore the voltage of the system is substantially equal to the voltage across the battery, according to the current drawn from the battery. The system then operates with a maximum inductor current sent to the inductor winding in accordance with the resistance of the winding and

  at the present voltage of the battery.

  Since the capacity of the alternator decreases as the speed of rotation decreases, such operation with a maximum inductive current is a common phenomenon in heavily charged electrical systems during periods of idle operation of the vehicle or in the case of a motor operation to

  other low speeds. Therefore, it is desirable

  table to increase the power output of the alternator. However, the capacity of the alternator is limited to idle, by several factors. Among these factors, the maximum allowable rotation speed of the alternator, which is calibrated for the maximum engine speed and a typical pulley ratio of about 3: 1, as is well known in the art. Therefore, the maximum idle speed depends on these factors and is

limited by them.

  Another limiting factor of the output is a factor to which the present invention is concerned, constituted by the temperatures of the components of the alternator. For some mid-range speeds, it becomes necessary to limit the output currents so that they are less than those theoretically possible to be delivered by the machine since these higher currents can lead to excessive component temperatures. That is why it was necessary for the designer to select an inductor winding which, when fully excited with the desired control voltage during such mid-range speed operation, provides lower output currents than those of which know they produce a

  thermal damage to the alternator components.

  This adversely affects the available capacity at rather low speeds, since the magnetic circuit of the alternator is never completely saturated for the lower voltage of the battery, even

with a maximum inductive current.

  In accordance with this, the present invention leads to the delivery of improved output power at low speeds and high speeds and prevents excessive heating of critical components in the alternator for midrange speeds. An alternator output control system having the features of the present invention includes an alternator having a magnetic rotor and winding assembly

  inductor, which is powered by an inductor winding current

  substantially at the system voltage. The food stream

  the inductor winding can produce an output current which, for certain speeds of rotation of the

  rotor, leads to a thermal overload of the alternator.

  Means are provided for controlling the current of the inductor winding to a total current in response to a comparison between a measured system voltage and a predetermined control voltage. The current of the field winding is increased when the measured system voltage is lower than the predetermined control voltage and is decreased when the measured system voltage is greater than the predetermined control voltage. The rotational speed of the alternator is detected and the current of the field winding is further controlled in response thereto so as to limit the current in the field winding to a value less than the total current of the field winding, when the rotational speed is within a predetermined range of rotational speeds corresponding to

  Limited heat dissipation of the alternator.

  More specifically, the invention relates to a device for controlling the output of an alternator, which comprises an inductor winding, an output winding and a rectifier coupled to loads of a vehicle, the alternator being coupled, to be rotatable, to a motor of a vehicle, the inductor winding being supplied, during the rotation of the alternator, by an excitation current on the basis of a system voltage not exceeding a standard regulated voltage of the system, the excitation current and the rotation of the alternator leading to the output of an output current in the output winding and in the rectifier for supplying vehicle loads to the system voltage, characterized in that that the device comprises:

  an inductive winding, which causes normal

  thermal overload of the alternator under the effect of an excessive output current when the excitation current sent to the inductor winding is

  greater than an excitation current limit, for certain

  n rotation speeds of the alternator;

  means for controlling the current of the winding

  inducing winding of the excitation current up to a maximum inductor winding current greater than the excitation limit current, in response to a comparison between

  a measured system voltage and a regulating voltage

  predetermined manner, said current control means

  of the inductor winding acting in such a way as to increase

  be the excitation current when the measured voltage of the

  system is lower than the preset control voltage

  terminated, and to reduce the excitation current when the measured system voltage is higher than the measured system voltage; and means for detecting the rotational speed of the alternator, the current control means of the inductor winding being sensitive to the speed of the alternator,

  rotation of the alternator to limit the current of exci-

  circulation in the exciter winding at the inductor limit current, for certain speeds of

rotation of the alternator.

  According to particular embodiments: said said rotational speeds of the alternator comprise a range of rotation speeds lower than a maximum rotation speed of the alternator and greater than a minimum rotation speed of the alternator;

  the means for controlling the current of the winding

  inductive current reduces the excitation current when the latter exceeds the excitation limit current and the rotation speed of the alternator is

  certain rotation speeds of the independent alternator

  the measured voltage of the system.

  The invention further relates to a device for controlling the output of an alternator, which comprises an inductor winding and an output winding, the alternator being rotatably coupled to a motor of a vehicle and sending a current to

  vehicle loads, at system voltage,

  in that the device comprises: an inductive winding which can be excited according to an excitation current, which is sent to it;

  means for controlling the current of the winding

  inductor for controlling the excitation current supplied to the inductor winding; means for detecting the system voltage; means for detecting the rotational speed of said alternator;

  the current control means of the winding

  inductor being able to control the excitation current.

  sent to the field winding in a permissible range of excitation currents between a minimum excitation current and a maximum excitation current,

  the inductor winding being characterized by its propensity

  sion to produce thermal conditions inside

  of the alternator likely to cause damage to the

  alternator, when the alternator is

  by an excitation current greater than an excitation limit current located between the minimum excitation current and the maximum excitation current, for certain rotation speeds of the alternator, the current control means of the winding inductor being adapted to respond to certain rotational speeds of the alternator for controlling the excitation current sent to the inductor winding so that it is between the minimum excitation current and the current

excitation limit.

  The invention also relates to a device for controlling the output of an alternator, which comprises an inductor winding and an output winding, the alternator being rotatably coupled to a motor of a vehicle and sending a current to

  vehicle loads, at system voltage,

  in that the device comprises: an inductor winding characterized by its propensity to produce a thermal overload in

  alternator when the inductor winding is

  by an excitation current greater than an excitation limit current, for certain rotational speeds of the alternator;

  current control means of the winding

  inductive means for applying the excitation current to the inductor winding to a maximum current of the inductor winding greater than the excitation limit current in response to a comparison between a measured system voltage and a predetermined control voltage, said current control means of the inductor winding acting to increase the excitation current when the measured voltage of the

  system is lower than the preset control voltage

  terminated, and reducing the excitation current when the measured system voltage is greater than the predetermined control voltage; and means for detecting the rotational speed of the alternator, the means for controlling the current of the excitation winding being able to respond to the speed of rotation of the alternator to limit the

  excitation current flowing in the inductive winding

  limit current when the alternator

  is at certain speeds of rotation.

  Other features and benefits of the

  present invention will emerge from the description given

  Hereinafter, taken in reference to the accompanying drawings, in which: - Figure 1 shows a graphical representation of the temperature characteristic of a component of the alternator according to the speed of the latter; FIG. 2 shows a graphical representation of the characteristic of the output current of the alternator

  depending on the speed of the latter for two alterna-

  drivers having inductive windings having different characteristics; FIG. 3 is a diagram of a conventional electrical vehicle system comprising an alternator and a regulating device that can be adapted for the implementation of the present invention; and FIG. 4 shows some modifications made to a known control device for setting

  implementation of the control according to the present invention.

  The limiting factor of the power of

  output, to which the present invention is directed, is the time

  components of an alternator. These components include predominantly different electronic components such as the bridge rectifier, the regulator

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  voltage and the (output) windings of the stator. Large amounts of heat in the case of intense output currents must be dissipated so that no damage to the components occurs. On the basis of objectives such as those aimed at reducing the point of view

  volume and dimensions the alternator module and the get-

  With limited airflow on temperature-sensitive components, for mid-range speeds, the alternator's ability to dissipate heat and prevent thermal damage is reduced. For example, in a typical six diode bridge device

  in which a conventional alternator can deliver

  At a current of up to 100 amperes, the power dissipated to heat under the effect of losses in the bridge alone is of the order of 200 watts. Since the heat sink associated with the bridge is reduced, as is desirable, in a manner compatible with the conditioning objectives and the air flow around the bridge is similarly reduced for the same purposes, the challenge which is to eliminate unwanted heat

becomes more and more difficult.

  A typical curve of temperature variations

  of an alternator component as a function of the speed of the latter is shown in Figure 1 appended to the

  present application and represents a characteristic of

  heat generation found in most modern automobile alternators. As can be seen from the figure, the generator temperatures are maximum at mid-range speeds between the speed designated Sl (low speed) and the speed designated S2 (high speed). The precise speeds S1 and S2 of the alternator vary from one type to another, but the basic form of the temperature response along the

  Alternator speed curve remains the same. That is,

  to say that maximum temperatures of the components

  fall for mid-range operating speeds. The low speed operation in the area to the left of S1 in the figure is characterized by a decreasing temperature of the components as the speed decreases. High speed operation in the area to the right of S2 in the figure is characterized in that the temperature of the components decreases as the speed increases. In the low speed range, the fact that the output current of the alternator is limited by a combination including the low speed and the lower voltage of the battery system, leads to a lower thermal input at the bridge, from weaker currents rectified in this bridge. At higher speeds, the increased air circulation by conventional fans or propellers coupled to the rotor shaft and the self-limiting feature of the alternator current result in an advantageous reduction of

  temperature when the speed increases.

  Referring now to Figure 3, there is shown a diagram of a typical automotive electrical system including an alternator and a control unit of this alternator. A vehicle electrical system, substantially as shown in FIG. 3, comprises a Lundell type alternator, designated

  generally by reference number 610. The alter-

  the inductor winding 620 is part of a rotor assembly, which is driven with the possibility of

  rotation by the engine 625 of the motor vehicle.

  The alternator is driven at a speed higher than the speed of the engine, by a belt and pulleys, a

well known way.

  The output terminals A, B and C of the three-phase stator windings are connected to respective AC input terminals of a full-wave three-phase bridge rectifier, generally designated by the reference numeral 630. The rectifier in bridge 630 has a DC ground terminal 635 coupled to the vehicle ground and a DC output terminal 637 coupled to the lead 638 for charging a battery 640 and supplying different vehicle loads represented by a resistor 670. The battery 640 is a conventional 12 volt automotive battery having a positive terminal 641 coupled to the conductor 638 and a

  negative terminal 643 coupled to the vehicle ground.

  The DC output terminal is further coupled to a switch 621 and a regulator 680 for controlling the excitation of the inductor winding.

  620. It is assumed here that the switch 621 is an interrup-

  solid state driver controlled by a PWM modulated signal present in line 624 and generated by regulator 680 as a function of the controlled system voltage via line 650 Such MID control is generally well known, and specific details of such control are disclosed in US Patent No. 4,636,706 filed by Bowman et al. The control control unit indicated by Bowman et al. Forms the basis of the control unit used in the preferred embodiment as will be described later, and therefore is incorporated herein by reference. We can find in this

  document a detailed description of the electrical system

  automobile represented schematically.

  Referring to FIG. 2, the inferred curve

  23 is the characteristic output current of a conventional type alternator. Mid-range speeds are represented between points S1 and S2 and correspond to a temperature-limited operating zone, as previously described. The speeds S1 and S2 also define ranges of low speeds and high speeds respectively on the left and

  to the right of said speeds S1 and S2.

  Starting with the midrange speed, it is assumed that there is a regulated system voltage with a fully energized inductor winding. That is, the field winding is supplied with current in accordance with the maximum permissible modulation of pulses in time for a set voltage of substantially 14 volts. This corresponds substantially to 100% of the pulse rate of the MID signal controlling the switching element of the inductor winding. The curve 23A between S1 and S2 therefore represents the maximum output current. The maximum output current should not exceed that which would cause thermal damage to the alternator components, and therefore determine the choice of a conventional inductor winding which, for a set voltage and a maximum pulse modulation in duration for the midrange speed itself limits the output current to a predetermined maximum allowable value. This value naturally varies with the specific alternator type and application. Moving to the left of Si on curve 23 and assuming the same electrical charge and the same current demand, it is assumed that the battery voltage of the battery system is obtained. Naturally, the voltage of the battery system is substantially equal to the voltage across the charged battery. Typically, this voltage is less than 10% to 20%, at the set voltage. The inductor winding is energized with a maximum pulse duration modulation for the battery system voltage and therefore the alternator circuit can operate at a saturation degree even lower than is the case in the mid-range speeds, which, as has been the case

  previously described, is limited on the basis of

  relating to the temperature of the components. Since it is assumed that the maximum inductive current is obtained for the lower voltage of the battery system, the curve corresponds to the maximum current delivered by

  the alternator with the chosen inductor winding.

  According to the present invention, a winding

  An inductor with a lower electrical resistance characteristic (low voltage inductor winding) is used instead of the inductor winding

  classic. In itself, one can obtain equivalent saturations

  nits of the magnetic circuit for lower voltages applied across the low inductor winding

  voltage relative to the conventional inductor winding.

  Or, in other words, the saturation of the magnetic circuit is higher for a low voltage inductor winding than for a conventional inductor winding unit voltage applied thereto. Based on the assumption that speeds higher than Si are characterized by a set system voltage and that speeds lower than S1 are characterized by a battery system voltage, the direct introduction of a low voltage inductor winding in the alternator allows to obtain a maximum output current in the range of operating speeds, as represented by the upper curve 25 in Figure 2. It can be seen that the output current is greater than that which can be obtained using a conventional inductor winding, in

  the whole range of operating speeds.

  However, remembering that the choice of the inductor winding is imposed by the maximum permissible output current for the mid-range speeds, the choice

  such a low-voltage inductive winding does not

  should not be part of the design objectives to prevent thermal overload. Such a low voltage inductor winding would lead to the production of high output currents that are unacceptable for an equivalent regulated system voltage for medium speeds.

  range, and of course at unusually high temperatures.

missibles of the components.

  The control unit according to the present invention

  allows to obtain an increased current capacity of the alter-

  for low speeds of rotation of the alterna-

  compared to conventional alternator systems, while also limiting the output current for midrange speeds sensitive to the critical temperature. By examining again FIG. 2, it can be seen that the present invention makes it possible to obtain a current profile.

14 2729018

  maximum output on the basis of portions of both the lower curve 23 of a conventional inductor winding and the upper curve of a low voltage inductor winding. The resulting profile of the output current as a function of the speed is represented essentially by the joining of the portion 25A of the upper curve 25 to the limit Si of the mid-range speeds, of the portion 23A of the lower curve for speeds of

  mid-range of Sl to S2, and part 25B of the cour-

  be greater than 25, from the S2 limit of midrange speeds to all higher operating speeds. The zone 27 provided with oblique hatching in the region of the mid-range speeds between the upper curve 25 and the lower curve 23 is a possible but undesirable operating zone that the control unit according to the present invention makes it possible to avoid. . In a preferred embodiment, a low voltage inductor winding is used in conjunction with

  with a numerically controlled voltage regulator.

  The inductor winding according to the present invention is a low voltage inductor winding and therefore does not provide the same inherent output current limiting characteristic which was hitherto employed by conventional alternators for midrange speeds. In contrast, the control unit according to the present invention responds to a range of speeds to reduce and / or limit the excitation of the low voltage inductor winding below a potential excitation, which limits the output current. to a value lower than a value that can potentially be obtained with the low voltage inductor winding. Outside mid-range speeds, the control unit allows

  the excitation of the low voltage inductor winding

  above what is allowed for medium speeds of

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  range, thereby increasing the output current by bringing it above the maximum values imposed until then

  by the characteristics of conventional inductive windings

  c. The hardware configuration according to Bowman et al. Is used here as the basis for a form

  preferred embodiment of the present invention. How-

  Of course, it will be appreciated that one of ordinary skill in the art can readily adapt a number of other control systems using pulse-modulated duration inducing winding current control unit or other methods. inductor winding current control, for the implementation of

  the present invention. In the description that follows,

  an attempt was made to limit to a minimum a repetition of the content of Bowman et al. The system according to Bowman et al. Is modified to include a low voltage field winding and is further modified in accordance with the features shown in Fig. 4 of the present application, as will be

described below.

  With reference to FIG. 4, there are shown modifications to the circuit of FIG. 6 of the Bowman et al. Document for carrying out the present invention. Any characteristic element of FIG. 4, to which an accent is attached, corresponds to an element provided with a similar reference numeral, but without the accent in the Bowman document, modified for the implementation of the invention. Any item designated by a numerical reference numeral greater than 500 is an element added to the circuit of Figure 6 of Bowman et al., To assist in the practice of the present invention. Other elements in Fig. 4, designated by reference numerals which also appear in Fig. 6 of the Bowman et al. Document, correspond to the elements of this figure 6 of the Bowman et al. Document and are represented again for clarity of explanation. and understanding the main operations for practicing the present invention. Starting from the upper right corner of FIG. 4, it is seen that the counter 270 is shown partially, with its outputs Q6-Q4. Next to the counter 270 is a bistable flip-flop 310 ', which is modified with respect to the bistable flip-flop 310 of Fig. 6 of the Bowman document and the like to include a resetting terminal R of the DC component. The output of the reference value comparator connected in the line 110 is connected to the terminal D of the flip-flop 310 '. The flip-flop 310 'is connected to the conductor 312, and the Q terminal of the flip-flop 310'

  is connected to the UP (progressive counting) terminal of the

  progressive / regressive 270 by means of the conductor 314.

  The logic level (high or low) present in the conductor 314 is such that it places the counter 270 in a progressive counting mode when the generator voltage is lower than the desired set value, and in a countdown mode when the generator voltage is greater than the set value. But, additionally, when the reset terminal R of the DC component of the flip-flop 310 'is at the high level, the input D of this flip-flop is prioritized and the logic level (up or down) present in line 314 is such that it places counter 270 in a counting mode

regressive.

  The Q6-Q4 output terminals of the counter 270 are connected to form three inputs terminating at a four input AND gate 517. The output of the AND gate 517 is connected to the reset terminal R of the DC component of the flip-flop 310 '. The fourth input of the AND gate 517 receives the signal "HOT SPEED" present in the line 515 and which takes a high logic state when the speed of the alternator is

  located between Sl and S2, as will be described later.

  The flip-flops 414 and 406 are connected to the inputs of a NAND gate 501. The output of the gate

  NAND 501 is connected to the flip-flop flip-flop

  511. Bistable flip-flops 511 and 509 are so-called low-speed flip-flops, since they determine the logic level (high or low) applied to the conductor 513. Therefore, terminal Q

  the flip-flop 509 is connected to the conductor 513.

  The R terminal of the flip-flop 511 is connected to the line 422. The flip-flop 509 is coupled to the line 442 and thereby is triggered by the Q output of the flip-flop 436. The signal present in line 513

  is a low-speed signal, which corresponds

  2300 rpm in the alternator, this low speed being considered as the lower limit Sl

mid-range speed.

  The conductor 513 is connected, so as to form an input, to the AND gate 505. The terminal Q of the flip-flop 420 (conductor 114) is connected by means of the inverter 503, as another input, to the AND gate 505. This input provides a high speed signal which corresponds substantially to 3000 rpm in the alternator, which high speed should be considered as the upper limit S2 for midrange speeds. These inputs and this transfer gate act to produce a logic level signal

  high in line 515, the signal HOT SPEED, unique-

  when the alternator speed is between S1 and S2. That is why a high-level HOT SPEED signal indicates alternator operation at a midrange speed. Speeds lower than Sl lead to the appearance of a low logic level signal in line 513 and therefore to a low logic level signal in line 515. Speeds greater than S2 lead to the occurrence of a logic high signal on the terminal Q of the flip-flop 420 and therefore the sending of a logic low signal to the AND gate 505 via the inverter 503, which also leads to a low logic level signal appears in line 515. For speeds below S2 and above Si, the two signals sent to the inputs of the AND gate 505 are high, which leads to the appearance of a signal at a high level in the line 515. The signal present in the line 515 thus renders the AND gate 517 only during the

  running at a midrange speed.

  High speed and low speed thresholds

  S1 and S2, as represented by the respective signals

  in lines 513 and 514, are fixed as examples

  and can be modified to suit the particular combination of alternator and engine, including the speed ratio between the engine and the alternator for

a particular application.

  The additional and modified elements cooperate to add another fifth mode of operation to

  the regulator control unit according to Bowman et al.

  This fifth mode of operation only acts for a mid-range operating speed. It has for

  effect of stopping the progressive counting of the progress meter

  sif-regressive 270 to a predetermined higher value, through the AND gate 517 and the flip-flop 310 ', this combination being referred to herein as the "hot speed lock system". Therefore, when operating at a mid-range speed, the meter can not progressively count to a full state and, as it progressively counts to the value allowed by the locking system hot speed, the value

  is such that the pulse rate of the inductive voltage

  can be 112/128 x 100 per cent, or about 87.5 per cent. Of course, other lock limits can be selected by selecting the appropriate bit combinations output from the Q6-Qo outputs of the up-down counter 270. Outside the mid-range speeds, the hot-lock system is deleted by applying a signal to

low level in line 515.

  When passing for the first time in the region of mid-range speeds between Sl and S2, one can have a pulse rate greater than 87.5%; in other words, the progressive-regressive counter may exceed the desired maximum value. The terminal R resetting of the DC component of the flip-flop 310 'is kept high in this case, under the effect of the

  high speed lock system. The counter

  In this case, it is possible to perform a count down only as long as its count value is equal to or greater than the desired maximum value, regardless of whether the system voltage is higher or lower than the desired set voltage. This sets the pulse rate

  to the appropriate desired value of 87.5%.

  Outside of midrange speeds, the Bowman et al. Governor control unit is unaffected by additions and modifications to the circuit. Therefore, the pulse rate present respectively below and above the speeds Sl and S2 may increase to its maximum value allowed by a higher locking system, not described in detail here, but described in detail. detailed manner in Bowman et al. With the insertion of the low voltage inductor winding in

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  the alternator, this leads to increased excitation by

  compared to that provided by the class inductor winding

  if that. That's why the output current is improved to

these speeds.

  It can then be noted that the currents available for speeds lower than the predetermined mid-range speeds are greater than those that can be obtained previously with an inductor winding and a conventional control unit. It should further be noted that the currents available for speeds above the predetermined mid-range speeds are, similarly, greater than those previously available with

  the inductor winding and the conventional control unit.

  However, the control according to the invention limits the excitement

  of the low voltage inductor winding according to the present invention so as to thereby prevent the occurrence of thermal overload currents for

midrange.

  Although an exemplary embodiment of the invention has been described by way of example, it is believed that many changes and modifications will occur.

  to the ordinary person skilled in the art and that consequently

  the described embodiment should be considered as an example and without any limiting character. It is

  why the invention is supposed to encompass all these changes

ments, modifications and variants.

Claims (5)

  A device for controlling the output of an alternator (610), which includes an inductor winding (620), an output winding (615) and a rectifier (630) coupled to loads (670) of a vehicle, alternator being rotatably coupled to a motor of a vehicle (625), the inductor winding being energized, upon rotation of the alternator, by an excitation current on the basis of a system voltage not exceeding a standard set voltage of the   system; the excitation current and the rotation of the alterna-   generator for delivering an output current in the output winding (615) and in the rectifier (630) for supplying vehicle loads (670) to the system voltage, characterized in that the device comprises: an inductor winding (620), which normally causes a thermal overload of the alternator (610) under the effect of an excessive output current when the excitation current supplied to the inductor winding (620) is greater than one excitation limit current, for certain rotational speeds of the alternator (> 51, <52); means (680,621) for controlling the current of   the inductor winding to send to the inductive winding   causing the excitation current up to a maximum current of greater than the excitation limit, in response to a comparison between a measured voltage (650) of the system and a predetermined control voltage,   said means (680, 621) for controlling the current of the coil.   inducing element which acts to increase the excitation current when the measured voltage (650) of the system is lower than the predetermined control voltage, and to reduce the excitation current when the measured voltage (650) of the system is greater than the measured voltage of the system; and 22 2729018   means (505-513) for detecting the rotational speed of the alternator, the inductor winding current control means being responsive to the rotation speed of the alternator for limiting the excitation current flowing in the generator; inductor winding (620) at the excitation limit current, for some   rotational speeds of the alternator (> 51, <52).   2. Device according to claim 1, characterized in that said certain rotational speeds of the alternator comprise a range of rotational speeds lower than a maximum rotation speed (52) of the alternator and greater than a rotational speed. minimum (51) of the alternator.   3. Device according to claim 2, characterized in that the means (680) for controlling the current of the inductor winding reduce the excitation current when the latter exceeds the excitation current limit and the rotation speed of the alternator is located at certain rotational speeds of the alternator regardless of the voltage measured system.   4. Apparatus for controlling the output of an alternator (610), which includes an inductor winding (620) and an output winding (615), the alternator being rotatably coupled to a motor (625) of a vehicle and sending a current to loads (670) of the vehicle, at a system voltage, characterized in that the device comprises:   an inductive winding (620) which can be excited   depending on a current of excitation, which is sent to him; means (680,621) for controlling the current of   the inductor winding to control the excitation current   sent to the inductor winding (620); means for detecting the voltage (680) of the 23 2729018   system; means for detecting the rotational speed of said alternator (505-513); the current control means (680,621) of the inductor winding being adapted to control the excitation current supplied to the inductor winding (620) within a permissible range of excitation currents between a   minimum excitation current and a maximum excitation current   the inductor winding (620) being characterized by   its propensity to produce thermal conditions in the   the alternator (610) which may cause damage in this alternator, when the alternator is supplied with an excitation current greater than an excitation limit current situated between the minimum excitation current and the maximum current of excitation, for certain rotational speeds of the alternator (> 51, <52),   the current control means of the inductive winding   being responsive to certain rotational speeds (51,82) of the alternator for controlling the excitation current supplied to the inductor winding so that it is between the minimum excitation current and the excitation current.   5. Device for controlling the output of an alternator (610), which comprises a winding   inductor (620) and an output winding (615), the alternator   converter (610) being rotatably coupled to a motor (625) of a vehicle and supplying current to vehicle loads at a system voltage, characterized in that the device comprises: an inductor winding ( 620) characterized by its   propensity to produce a thermal overload in the alter-   generator (610) when the field winding is supplied with an excitation current greater than an excitation limit current, for certain rotational speeds of the alternator (> 51, <52); means (680,621) for controlling the current of   the inductor winding to apply the excitation current   inductor winding (620) to a maximum current of the inductor winding greater than the excitation limit current in response to a comparison between a measured voltage (650) of the system and a predetermined control voltage, said current control means of the inductor winding acting to increase the excitation current when the measured system voltage is lower than the predetermined control voltage, and to reduce the excitation current when the measured system voltage is greater than the predetermined control voltage; and means (509-513) for detecting the rotational speed of the alternator, the current control means of the excitation winding being adapted to respond to the rotational speed of the alternator for   limit the excitation current flowing in the winding   inductive current at the excitation limit current when the alternator rotational speeds (> 51, <52).