EP2102670A1

EP2102670A1 - Method and device for detecting the failure of an excitation circuit of a polyphase alternator

Info

Publication number: EP2102670A1
Application number: EP07858741A
Authority: EP
Inventors: Jean-Marie Pierret; Philippe Masson
Original assignee: Valeo Equipements Electriques Moteur SAS
Current assignee: Valeo Equipements Electriques Moteur SAS
Priority date: 2006-12-20
Filing date: 2007-11-27
Publication date: 2009-09-23
Also published as: FR2910639A1; US8618829B2; FR2910639B1; WO2008074952A1; US20120161810A1

Abstract

The method of detecting the failure of the excitation circuit of a polyphase alternator controlled by a regulator comprises the following steps: a) electrical information (Iexc) is continuously taken from the excitation circuit (1); b) the electrical information taken in step a) is continuously compared with a predetermined threshold value (Iref); c) a logic state (LT) is continuously determined according to the result of the comparison made in step b); and d) if the logic state (LT) determined in step c) persists for a time at least equal to a predetermined delay time (6), an electrical continuity fault of said excitation circuit is signalled. This method is particularly suitable for machines having a rotor equipped with permanent magnets or having a high remanence of the magnetic circuit of the rotor.

Description

METHOD AND DEVICE FOR DETECTING THE FAILURE OF THE EXCITATION CIRCUIT OF A POLYPHASE ALTERNATOR

TECHNICAL FIELD OF THE INVENTION

The present invention relates to a method and a device for detecting the failure of the excitation circuit of a polyphase alternator. The invention also relates to the polyphase alternator comprising this detection device.

BACKGROUND ART OF THE INVENTION. For obvious safety reasons, the important equipment of a motor vehicle is provided with detection and signaling devices for any operating anomaly.

The on-board generator, generally consisting of an alternator whose phase voltages are rectified, is one of these important equipments, and any driver knows the location of the red light called "charge" on the dashboard. his car.

The generalization of the use of electronics in vehicles, often replacing the electromechanical elements, allows an ever more fine detection of malfunctions and the circumstances of faults, for diagnostic or signaling purposes.

For example, the electronic voltage regulator described in the patent FR2642580 comprises defect detection means which analyze the concordance between different accessible parameters. In this patent application, particular analysis is made of the match between: the voltage at the output of the alternator and the voltage at the terminals of the inductor;

- the output voltage of the alternator and the voltage across the phase inputs.

The second case allows indirect detection of the following defects:

- lack of rotation of the alternator (broken belt);

an open excitation circuit (open inductor winding, broom jammed in its housing, etc.).

According to the teaching of document FR2642580, the following is called:

UB: the output voltage of the alternator (or the battery that is connected to the alternator). A: a regulation setpoint. Up: the amplitude of the phase signals. n predetermined phase voltage threshold below which it is considered that the alternator can not charge the onboard network: Vs2 <UB state of the charge indicator (lamp, LED, LCD ...), taking the value 0 if n There is no fault detected (LED off), or the value 1 if a fault is detected (LED lit).

A load defect is detected when the voltage UB delivered by the alternator is lower than the regulation setpoint Un when loads are applied, and the amplitude Up of the phase voltage is lower than the threshold Vs2 despite a set-up full-field condition of the alternator, that is, that we have the relation:

If UB <Un and Up <Vs2, then LT = 1 (light on)

The method of indirect detection of the failure of the excitation circuit of a polyphase alternator described in document FR2642580 is however not entirely satisfactory. Indeed, new alternators often include permanent magnets fixed on the magnetic circuit of the inductor (rotor). These magnets strongly increase the remanent magnetic flux in the alternator.

In the absence of excitation current, the phase signals can reach large amplitudes at high rotational speeds. It is even possible to charge the alternator without excitation current, which remains acceptable if the flow rate remains low enough to be absorbed by the permanent loads present in the vehicle. However, the energy produced by the magnets alone is not sufficient to maintain the voltage on the on-board network when feeding large loads. In case of breakage of the inductor winding, the amplitude decrease of the phase signals does not exist beyond a certain speed of rotation with the magnet rotors.

Consequently: the amplitude decrease of the phase signals can not be used to detect a continuity fault in the excitation circuit (inductor winding cut, brushes jammed in its housing and no longer bearing on the track ...), because the teaching of the document FR2642580 always leads to the relation:

If UB <Un and Up> Vs2, then LT = 0 (lamp off, no fault detection). GENERAL DESCRIPTION OF THE INVENTION

The present invention therefore aims to overcome the disadvantage of this lack of detection. It relates specifically to a method of detecting the failure of the excitation circuit of a polyphase alternator controlled by a regulator, the method comprising steps of:

a) continuously taking electrical information from the excitation circuit; - b) continuously compare the electrical information taken in step a) to a predetermined threshold value;

- c) continuously determine a logic state based on the result of the comparison performed in step b); and

- d) if the logic state determined in step c) persists for a duration at least equal to a predetermined time delay, report a lack of electrical continuity of the excitation circuit.

According to another particular characteristic, the electrical continuity fault signaling is made only if it is detected, as an additional condition, a command in the regulator for supplying a maximum current to the excitation circuit.

According to a particular embodiment, the electrical information taken is an excitation current and the threshold value is a predetermined reference current.

According to another particular embodiment, the electrical information taken is a waste voltage of a switching transistor of the excitation circuit and the threshold value is a predetermined reference voltage.

The invention also relates to a device for detecting the failure of the excitation circuit of a polyphase alternator suitable for implementing the method described above. In a first particular embodiment, the device according to the invention applies to an excitation circuit comprising a first switching transistor connected in series with an inductor of the alternator at the terminals of a supply voltage source. . - AT -

The device is notable in that it preferably comprises a second transistor connected in series with a reference current source across the supply voltage source. This second transistor operates as a current mirror of the first switching transistor, and delivers a measuring current proportional to the excitation current present in the first transistor.

Advantageously, the device further comprises a resistor and a first clipping diode connected in series across the inductor, a second clipping diode connected in parallel across the reference current source, and a circuit for producing said logic state as a function of first and second logic levels respectively present at the terminals of the first and second clipping diodes.

In a second particular embodiment, the device according to the invention applies to an excitation circuit also comprising a switching transistor connected in series with an inductor of the alternator at the terminals of a supply voltage source. .

The device is remarkable in that it preferably comprises a voltage comparator, a first input of this comparator being connected to a first terminal common to the inductor and to the switching transistor, a second input of the comparator being connected by the intermediate of a reference voltage source to a second terminal common to this switching transistor and to the supply voltage, and the output of the comparator being connected to a circuit for producing said logic state.

In one and the other particular embodiments of the invention, it is advantageous that the circuit for producing said logic state comprises a timer circuit.

The invention also relates to a polyphase alternator and an alternator-starter comprising a device for detecting the failure of the excitation circuit as described above.

These few essential specifications will have made obvious to the skilled person the advantages provided by the invention compared to the state of the prior art.

The detailed specifications of the invention are given in the following description in conjunction with the accompanying drawings. It should be noted that these drawings other purpose than to illustrate the text of the description and in no way constitute a limitation of the scope of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is the block diagram of the first embodiment of the device for detecting the failure of the excitation circuit of a polyphase alternator according to the invention.

Figure 2 is the block diagram of the second embodiment of the device for detecting the failure of the excitation circuit of a polyphase alternator according to the invention.

Figure 3 shows a time diagram of the normal mode excitation current and the detection signal in the absence of excitation circuit failure.

Figure 4 shows a time diagram of the excitation current in full field mode and the detection signal in the absence of failure of the excitation circuit.

Figure 5 shows a timing diagram of the excitation current as a result of a "full field" control and the detection signal in case of failure of the excitation circuit. Figure 6 shows a timing diagram of the excitation current as a result of a "full field" control and of the detection signal at the time of the failure of the excitation circuit.

DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION In the case where the magnetic circuit of an alternator comprises permanent magnets, or has a high remanence, it is therefore not possible to indirectly detect a failure of the excitation circuit by the absence of phase signals.

The solution to this problem is to notice that in case of breakage of the excitation circuit, the output voltage of the alternator decreases when charges are applied. The regulator then switches to the full-field state in order to provide a predetermined maximum excitation current Imax, for example 5 A. Under these conditions, it is sufficient to measure the value of the excitation current or the waste voltage of the transistor supplying the inductor, and to compare them with predetermined threshold values: a) If the excitation current is large, or if the waste voltage is high, the inductor winding is not cut. b) If the excitation current is zero, or if the waste voltage is low, the inductive winding is cut off.

This fault detection mode is added to the modes already implemented in an existing controller, such as that described in document FR2642580, and does not replace them.

The method according to the invention is based on the addition of a logic relation which involves the level of the excitation current or the voltage of the power transistor supplying the inductor and the level of the output voltage UB by relative to the setpoint voltage One. Preferably, the new logical relation has the following arguments:

UB: rectified output voltage of the alternator (or voltage of the battery which is connected to the alternator); A: control voltage regulation, lexc: excitation current; Iref: predetermined reference current, that is to say a predetermined excitation current threshold below which it is considered that the excitation circuit is open when UB <Un;

LT: logical state of a detection signal of the failure of the excitation circuit, or state of the charge indicator (lamp, LED, LCD ...), taking the values:

LT = O if there is no fault detected (the light is off); LT = 1 if a fault is detected (the indicator is lit). The detection condition of an open excitation circuit is realized in this case by a simple logical OR: Table 1

Alternatively, if the regulator does not have means for measuring the excitation current lexc, the same result is obtained by measuring the voltage of the excitation transistor.

Is :

Von: drop voltage of the excitation transistor in the full field state. Vref: predetermined threshold Von below which it is considered that the excitation circuit is open when UB <Un.

In this case, the logic state LT of the detection signal is then determined by the relation:

UB

UB <One UB> One

von

Table 2

Von <Vref LT = 1 LT = 0

Von> Vref LT = 0 LT = 0

The detection of the decrease of the battery voltage (that is to say when UB <Un) is ensured by the setting of the field inductor in full field.

The delay present in the fault detection circuits of an existing regulator, such as that described in the document FR2642580, naturally achieves this detection (of the order of 300 ms). This delay only detects confirmed faults of greater duration than the duration of this delay and for which the cutting of the excitation has disappeared. In the event of a fault, the controller remains in a determined stable state, which is the case when the inductor is switched off (full field status).

FIG. 1 represents a first embodiment of a device for detecting the failure of the excitation circuit of a polyphase alternator according to FIG. the invention, implementing the method of measuring the excitation current lexc (Table 1).

In a manner known per se, the induction coil 1 of the alternator is supplied from the battery voltage UB by a power electronics comprising a first switching transistor 2 and a free-wheeling diode 3.

In a manner also known, defects other than the failure of the excitation circuit are indicated by a charge indicator 4, one terminal of which is connected to the battery voltage UB, and the other terminal of which is switched to ground by a transistor 5 controlled by the output signal of a timer circuit 6.

The timer circuit 6, which preferably provides a delay of 300 ms, is triggered by the output signal of a first NOR circuit 7, the inputs of which receive logic levels F1, F2 representative of the various faults of the alternator. , and associated power electronics. In addition to these known elements, a resistor 8 in series with a first Zener diode 9 is connected in series across the winding of the inductor 1. This first clipping diode 9 limits the excitation signal to logic levels ( for example: 5 V).

A second transistor 10 is also added. It operates in mirror with the first switching transistor 2 delivering a low lexc / n current, but proportional to the excitation current lexc.

If lexc = 5A and n = 100, the current Iref / n delivered by the second transistor 10 is equal to 50 mA, which corresponds to a full-field state with a good inductor. If the winding of the inductor 1 is cut off, the value of lexc / n falls to a value equal to zero, or close to zero.

The cut-off detection of the winding of the inductor 1 is done by comparing the current lexc / n to a source of reference current 1 1 fixed to an intermediate value (for example: Iref / n = 25 mA). A second zener diode

12 sets the amplitude of the voltage across the reference current source 1 1 to be compatible with logic levels (for example: 5 V).

A detection signal LT of the failure of the inductor 1 is produced from a first logic level present on the anode of the first Zener diode 9, and a second logic level present on the anode of the second Zener diode 12. The first logic level is applied to the input of an inverter circuit 13 whose output is connected to an input of a second NOR circuit 14; the second logic level is applied to another input of this second NOR circuit 14.

The output of the second NOR circuit 14 is connected to an input of the first NOR circuit 7.

In normal regulation, the switching of the first switching transistor

2 is such that the input of the inverter circuit 13 passes through the logic levels 0 and 1, lexc / n is less than or passes on either side of the reference value Iref / n, and the levels of the inputs of the second circuit NOR 14 produce a level 0 at the output (or a succession of levels 0 and 1).

As a result, the output of first NOR circuit 7 remains at level 1 or passes successively through logic levels 0 and 1. The timer circuit 6 is permanently reset, and there is no fault detection.

When the voltage UB drops at the output of the alternator and the winding of the inductor 1 is not cut off, the first switching transistor 2 is full field, but lexc / n is always greater than the reference value Iref / n, the second logic level and the corresponding input of the second NOR circuit 14 are always at level 1, so that its output remains at level 0.

In the absence of other detected faults on the logic levels F1 and F2, the corresponding input of the first NOR circuit 7 remains at level 1, and the timer circuit 6 is inhibited: there is no detection of default.

In the event of a break in the winding of the inductor 1, the regulator seeks to set full field, the input of the inverter circuit 13 goes to level 1 and its output goes to level 0. On the other hand, the voltage across the terminals of the reference current source 1 1 falls to the ground potential (level 0). The output of the second NOR circuit 14 therefore goes to logic level 1, and the output of the first NOR circuit 7 therefore passes to level 0.

If the breakage of the winding of the inductor 1 is confirmed, the output of the first NOR circuit 7 is maintained at the level 0, as well as the resetting input R of the timer circuit 6. As a result, the timer circuit 6 is triggered , and its output goes to level 1 after 300 ms.

The control transistor 5 of the charge indicator 4 is then turned on, which has the effect of signaling the failure of the inductor 1. A second embodiment of a device for detecting the failure of the excitation circuit of a polyphase alternator according to the invention is shown in FIG. 2. This second embodiment alternately implements the method consisting in measuring the waste voltage of the switching transistor 2 of the excitation circuit (Table 2).

We find the known elements already used in the first embodiment, that is to say:

an inductive winding 1;

a switching transistor 2; a freewheeling diode 3;

- a charge indicator 4;

a transistor 5 which switches this charge indicator with respect to a fixed potential (ground);

a NOR circuit 7 taking into account all the faults F1, F2 detected by the specific means internal to the regulator.

- a timer circuit 6.

In addition to these elements, the mounting of a voltage comparator 15 makes it possible to compare the voltage drop Von of the switching transistor 2 with a reference voltage Vref of a reference voltage source 16. When the regulator is in the field , and that the excitation current is maximum, the voltage of waste Von is important (for example: 200 mV).

In the event of a break in the inductor winding, the regulation loop tends to control the supply of a maximum excitation current Imax. Since this maximum excitation current Imax can not be established, the waste voltage Von remains zero or close to zero.

It suffices to choose a value of Vref between these two values, for example of 50 mV, to detect a break in the winding of the inductor 1.

An advantage of this second embodiment in the first embodiment is that the combination of the switching transistor 2 and the voltage comparator 15 makes it possible to directly detect the breaking of the winding of the inductor 1 without the need for another NO circuit. OR.

In normal regulation, the switching transistor 2 is cut out so that Von is alternately lower and higher than the reference voltage Vref; therefore, the outputs of the voltage comparator 15 and the NOR circuit 7 pass successively through logic levels 0 and 1. The timer circuit 6 is permanently reset, and there is no fault detection.

When the output voltage UB of the alternator drops, and the winding of the inductor 1 is not cut off, the switching transistor 2 is full field, the waste voltage Von is greater than 50 mV, the output of the voltage comparator 15 is at logic level 0, the output of the NOR circuit 7 is at level 1, and the timer circuit is inhibited: there is no fault detection.

In the event of a break in the winding of the inductor, the output voltage UB of the alternator drops, the switching transistor 2 is full field, but the waste voltage Von is less than 50 mV and the output of the voltage comparator 15 is at logic level 1. The fault is detected after the delay of 300 ms imposed by the timer circuit 6.

In order to illustrate the operation of the devices described above, FIGS. 3, 4, 5 and 6 show the logic state of the detection signal LT, or of the charge indicator, as a function of the lexc excitation current in different modes. operating the alternator.

FIG. 3 shows, in normal operating mode of the alternator, the waveform 17 of the excitation current lexc, whose amplitude and the duty cycle are determined by the control loop. In this mode, the duty cycle is less than 1, and the intensity of the excitation current lexc remains lower than the maximum intensity Imax.

The detection signal LT of a failure of the inductor remains at logic level 0.

FIG. 4 represents the case where the excitation current lexc is continuous and of maximum intensity Imax, that is to say the case where the regulator has received a "full field" command. The detection signal LT remains at logic level 0, that is to say that the excitation circuit is in good condition, and that the alternator is indeed in full field mode.

FIG. 5 shows the case of a break in the winding of the inductor 1. The regulator has received a "full field" command, but the excitation current lexc is zero.

The detection signal LT of a failure of the inductor is at logic level 1. As shown in FIG. 6, the timer circuit 6 causes a delay of 300 ms between the moment 18 of the breakage of the winding of the inductor 1 and the moment 19 when the detection signal LT passes to the logic level 1.

It goes without saying that the invention is not limited to the only preferred embodiments described above.

In particular, the particular values of the intensities, voltages and the delay specified above are only given as examples.

It is the same for particular types of discrete elements, analog circuits or logic cited: they could, alternatively, be replaced by other electronic components performing the same functions.

On the contrary, the invention embraces all the possible embodiments that would remain within the scope defined by the claims below.

Claims

1) A method for detecting the failure of the excitation circuit of a polyphase alternator controlled by a regulator, said method comprising steps of: a) continuously taking electrical information (lexc; Von) in said excitation circuit; ;

- b) continuously compare the electrical information taken in step a) to a predetermined threshold value (Iref, Vref);

c) continuously determining a logical state (LT) as a function of the result of the comparison performed in step b);

- d) if the logic state (LT) determined in step c) persists for a duration at least equal to a predetermined time delay (6), report a lack of electrical continuity of said excitation circuit.

2) A method of detecting the failure of the excitation circuit of a polyphase alternator according to claim 1, suitable for implementation in an alternator comprising a rotor with permanent magnets or a rotor with a strong remanence of the magnetic circuit, characterized in that said electrical continuity fault signaling is made only if it is detected, as an additional condition, a command in said regulator for supplying a maximum current (Imax) to said excitation circuit.

3) Process according to claim 1 or 2, characterized in that said electrical information taken is an excitation current (lexc) and said threshold value is a predetermined reference current (Iref).

4) Method according to claim 1 or 2, characterized in that said electrical information taken is a voltage drop (Von) of a switching transistor (2) of said excitation circuit and said threshold value is a reference voltage ( Vref) predetermined. 5) Device for detecting the failure of the excitation circuit of a polyphase alternator adapted to the implementation of the method according to claim 3, said excitation circuit comprising a first switching transistor (2) connected in series with a inductor (1) of said alternator at the terminals of a supply voltage source (UB), characterized in that it comprises a second transistor (10) connected in series with a reference current source (11) across said supply voltage source (UB), said second transistor (10) operating in current mirror of said first switching transistor (2), and delivering a measurement current (lexc / n) proportional to said excitation current (lexc present in said first transistor.

6) Device for detecting the failure of the excitation circuit of a polyphase alternator according to claim 5, characterized in that it further comprises a resistor (8) and a first clipping diode (9) in series mounted. in branching across said inductor (1), a second clipping diode (12) shunt-connected across said reference current source (1 1), and a producing circuit (6, 7, 13, 14 ) of said logic state (LT) as a function of first and second logic levels present respectively at the terminals of the first and second clipping diodes (9, 12).

7) Device for detecting the failure of the excitation circuit of a polyphase alternator adapted to the implementation of the method according to claim 4, said excitation circuit comprising a switching transistor (2) connected in series with an inductor (1) said alternator across a supply voltage source (UB), characterized in that it comprises a voltage comparator (15), a first input of said voltage comparator (15) being connected to a first terminal common to said inductor (1) and said switching transistor (2), a second input of said voltage comparator (15) being connected via a reference voltage source (16) to a second terminal common to said transistor of switching (2) and at said voltage power supply (UB), and the output of said voltage comparator (15) being connected to a generating circuit (6, 7) of said logic state (LT).

8) Device for detecting the failure of the excitation circuit of a polyphase alternator according to any one of claims 5 to 7, characterized in that said circuit for producing (6, 7, 13, 14) said logic state. comprises a timer circuit (6).

9) polyphase alternator comprising a device for detecting the failure of the excitation circuit according to any one of claims 5 to 8.

10) alternator-starter comprising a device for detecting the failure of the excitation circuit according to any one of claims 5 to 8.