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

• US 20120161810A1
• Filed: 11/27/2007
• Published: 06/28/2012
• Est. Priority Date: 12/20/2006
• Status: Active Grant

• Current Assignee: Valeo Equipements Electriques Moteur (Valeo SE)
• Original Assignee: Valeo Equipements Electriques Moteur (Valeo SE)
• Inventors: Pierret, Jean-Marie, Masson, Philippe
• Granted Patent: US 8,618,829 B2
• Time in Patent Office: Days
• US Class Current: 324/765.01
• CPC Class Codes: G01R 31/343 in operation
• CPC Class Codes: G01R 31/346 Testing of armature or field windings
• CPC Class Codes: G01R 31/54 Testing for continuity
• CPC Class Codes: H02P 9/305 controlling voltage H02P9/302 takes precedence

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.

Claims

1. Method for detecting the failure of an excitation circuit of a polyphase alternator controlled by a regulator, said method comprising the following steps:

a) electrical information (Iexc;

Von) is continuously taken from said excitation circuit;

b) the electrical information taken in step a) is continuously compared with a predetermined threshold value (Iref, Vref);

c) a logic state (LT) is continuously determined according to the result of the comparison made in step b);

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.

2. Method for detecting the failure of an excitation circuit of a polyphase alternator according to claim 1, suitable for use in an alternator having a rotor with permanent magnets or a rotor having a high remanence of the magnetic circuit, wherein said electrical continuity fault is only signalled if, as supplementary condition, a command is detected in said regulator to supply a maximum current (Imax) to said excitation circuit.

3. Method according to claim 1, wherein said electrical information taken is an excitation current (Iexc) and said threshold value is a predetermined reference current (Iref).

4. Method according to claim 1, wherein said electrical information taken is a breakdown voltage (Von) of a switching transistor (2) of said excitation circuit and said threshold value is a predetermined reference voltage (Vref).

5. Device for detecting the failure of an excitation circuit of a polyphase alternator according to claim 3, said excitation circuit comprising a first switching transistor (2) mounted in series with a field winding (1 ) of said alternator at the terminals of a supply voltage source (UB), wherein said device contains a second transistor (10) mounted in series with a reference current source (11) at the terminals of said supply voltage source (UB), said second transistor (10) serving to mirror the current from said first switching transistor (2 ), and delivering a testing current (Iexc/n) proportional to said excitation current (Iexc) present in said first transistor.

6. Device for detecting the failure of an excitation circuit of a polyphase alternator according to claim 5, it wherein said device also includes a resistor (8) and a first peak-clipping diode (9) in series shunted to the terminals of said field winding (1), a second peak-clipping diode (12) shunted to the terminals of said reference current source (11), and a gate (6,7,13,14) generating said logic state (LT) as a function of first and second logic levels present at the terminals of the first and second peak-clipping diodes (9,12) respectively.

7. Device for detecting the failure of an excitation circuit of a polyphase alternator according to claim 4, said excitation circuit containing a switching transistor (2) mounted in series with a field winding (1) of said alternator at the terminals of a supply voltage source (UB), wherein said device includes a voltage comparator (15), a first input of said voltage comparator (15) being connected to a first terminal common to said field winding (1) and to said switching transistor (2), a second input of said voltage comparator (15) being connected by means of a reference voltage source (16) to a second terminal common to said switching transistor (2) and to said supply voltage (UB), and the output of said voltage comparator (15) being connected to a gate (6, 7) for generating said logic state (LT).

8. Device for detecting the failure of an excitation circuit of a polyphase alternator according to claim 5, wherein said gate (6,7,13,14) for generating said logic state contains a delay circuit (6).

9. Polyphase alternator containing a device for detecting the failure of the excitation circuit according to claim 5.

10. Alternator-starter containing a device for detecting the failure of the excitation circuit according to claim 5.