SENSOR FOR REGISTRATION OF LEAK CURRENT

Abstract: A sensor for registration of leak current between metal element (12) in a vehicle's chassis or body and electric wires that run along said metal element. The sensor includes at least one resistor bridge connection connected between the vehicle's poles (10, 11). One side of the bridge connection is connected to said metal element (12) and the other side forms a reference point (13) for a detection circuit connected between said point (13) and metal elements (12), said detection circuit including devices (16, 20) for registration of leak current.

Description: SENSOR FOR REGISTRATION OF LEAK CURRENT TECHNICAL AREA The present invention refers to a sensor for registration of leak current between metal elements in a vehicle's chassis or body and electric wires that run along said metal ele¬ ments. BACKGROUND OF THE INVENTION In almost all electric vehicles there is electric energy which is classified within the concept high-tension current, which is considered as dangerous for man. For instance,ele¬ ctric vehicles occur with voltages up to 400 volt and cur- rents of approximately 500 ampere. Many electric vehicles work in a difficult environment with presence of moisture, dirt, dust and vibrations. If any leak currentfault occurs in the electric vehicle's high-tension current system this can be very dangerous from the aspect of personal safety. Danger arises as soon someone touches a component (or moisture/fluid upon said component), e.g. by connection of mains current for charging of batteries or for service and inspection. If a fault already exists in some component a second fault can cause an explosion in batteries or other critical electric components. Already a minor collision can cause damages onto the vehicle's cabling. An earth fault breaker is used to detect a leak current between phase and earth by A.C.-apparatus, whereby the current is cut off as soon as a fault is detected. These devices are based on detection of a difference of current between conductor and reconductor and is therefore not possible to apply onto electric vehicles where considerable parts of chassis and body consists of metal which can be electric conducting. THE PURPOSE AND MOST IMPORTANT FEATURES OF THE INVENTION The purpose of the present invention is to achieve a effi¬ cient leak current-detector for electric vehicles. This purpose is achieved with the invention by means of at least one resistorbridgeconnection including resistors adapted for high registrationsensitivity, which bridgecon- nection is connected between the vehicle's poles, whereby one side of the bridge is connected to said metal elements and the other side forms a reference point for a detection- circuit connected between said point and the metal elements, said detectioncircuit including devices for registration of leak current. DESCRIPTION OF THE FIGURE The invention will be described herebelow with reference to the embodiment that is shown in the enclosed drawing. DESCRIPTION OF EMBODIMENT The figure discloses a resistorbridgeconnection with the resistors Rl, R2, R3, R4, R5 and R6, that is connected between the plus- and minus poles in a electric vehicle's cabling at the points 10 respectively 11. The point 12 is connected to the vehicle's body (point of electric earth), i.e. any voltage is balanced to the body. On the opposite side of the bridge the point 13 forms a point of reference and is equivalent to an artificial earth. The resistors R3 and R4 have the same resistance, which should be chosen so that it is approximately five times higher than a chosen detectionvalue for the leak current- resistors R5 and R6 (inverted proportional to the limit for the leak current 15 or 16). The resistors Rl and R2 have the same resistance, which should be less than a fifth of the resistance for R3 and R4 where one must consider the power outlet. A detection circuit is connected between the point of elec¬ tric earth 12 and the point 13. The detection circuit in¬ cludes the resistors R7, R8 and means 15, 16 for registra¬ tion of leak current, which are exemplified by optoswitches, which are used for galvanic separated transfer of signals. If for instance a short-circuit-fault (= the resistor R6) arises between the point of grounding 12 and the minuscon- ductor to the point 11 the resistor R4 becomes short-cir¬ cuited. Hereby occurs an imbalance in the resistorbridgecon- nection and a currentflow is formed through the resistor R3 and also parallel to this via the resistors Rl, R2 and also parallel through the detection circuit's resistors R8, R7 and through a in the optoswitch 16 arranged diode 17. The diode 17 activates the optoswitchexit 18 witch is connected with a secondary circuit and a output signal is received at 19. The output signal then control a non shown device to interrupt the current quickly at the source of supply. If on the other side a short-circuit-fault (= resistor R5) arises between the point of grounding 12 and the plusconduc- tor to the point 10 becomes the resistor R3 short-circuited. Hereby arises an imbalance on the other side of the resis¬ torbridgeconnection and a currentflow is formed trough the resistor R4 and parallel with this via the resistors Rl, R2 and also parallel through the detection circuit's resistors R7, R8 and through the in the optoswitch 15 arranged diode 20. The diode 20 activates exit 21 on the optoswitch witch is connected with the secondary circuit, and a output signal is received at 22. The output signal then control the device so that the current is quickly interrupted at the source of supply. As the secondary circuit has two exits 19, 22 one can recei¬ ve information on which of the conductors the leak current appears. At an embodiment of the invention adapted for 220 volt alternating current, the resistors Rl, R2 each has a resis¬ tance of approximately 10 kΩ, the resistors R3, R4 each has a resistance of approximately 50 kΩ, the resistor R7 a resistance of approximately 100 Ω, the resistor R8 a resis- tance of approximately 500 Ω and the resistors R9, R10 each a resistance of approximately 10 kΩ. The values of detection for the resistances R5, R6 thereby amount to approximately 20-25 kΩ. The device according to the invention can be used as well for direct current as for alternating current. In an alter¬ nating current application with three phases, can three devices according to the invention be connected with each other in a starshaped form with the bodyconnection as cen- tre. The invention is not limited to the above described embodi¬ ments, instead more variants are conceivable within the scoop of the invention. For instance, the optoswitches can be replaced with suitable relays.

Claims: CLAIMS 1. Sensor for registration of leak current between meta- lelement (12) in a vehicle's chassis or body and electric wires that run along said metal element, c h a r a c t e r i z e d t h e r e o f, that at least one resistorbridgeconnection comprising the resistors (R3, R4) adapted for high registrationsensitivity, which bridgeconnection is connected between the vehicle's poles (10, 11), whereby one side of the bridge is connected to said metal element (12) and the other side forms a refe¬ rence point (13) for a detectioncircuit connected between said point (13) and the metal elements (12), said detection- circuit including devices (16, 20) for registration of leak current. 2. Sensor according to claim 1, c h a r a c t e r i z e d t h e r e o f, that the devices (16, 20) for registration of leak current includes means for quick interruption of the current via the electric wires. 3. Sensor according to claim 1 or 2, c h a r a c t e r i z e d t h e r e o f, that the devices for registration of leak current consist of at least one for each electric pole and respective phase ar¬ ranged optoswitch (16, 20). 4. Sensor according to claim 3, c h a r a c t e r i z e d t h e r e o f, that the devices (16, 20) for registration of leak current include separate signaloutlets (19, 22) for each electric pole and respective phase, for indicating which of the wires having part in the leak current. 5. Sensor according to any of preceding claims, c h a r a c t e r i z e d t h e r e o f, that it includes several resistorbridgeconnections placed onto different places in the electric system of the vehicle, and connected to common registration devices. 6. Sensor according to any of preceding claims, for use in alternating current systems with several phases, c h a r a c t e r i z e d t h e r e o f, that several resistorbridgeconnections are mutually con- nected with the metalelementconnection (12) forming the centre of a starconnection. AMENDED CLAIMS [received by the International Bureau on 25 February 1994 (25.02.94); original claims 1-6 replaced by amended claims 1-6 (2 pages)] 1. A sensor for registration of any leak current between metal elements (12) in a vehicle's chassis or body and elec¬ tric wires that run along said metal elements, c h a r a c t e r i z e d in that at least one resistor bridge connection comprising resistors (R3, R4), adapted for high registration sensitivity, is connected between the battery poles (10, 11) of the vehicle, wherein one side of the bridge is connected to said metal element (12) and the other side forms a reference point (13) for a detection circuit connected between said point (13) and the metal elements (12), said detection circuit including devices (16, 20) for registration of any leak current. 2. A sensor according to claim 1, c h a r a c t e r i z e d in that the devices (16, 20) for registration of any leak current includes means for quick interruption of the current via the electric wires. 3. A sensor according to claim 1 or 2, c h a r a c t e r i z e d in that the devices for registra¬ tion of any leak current consist of at least one optoswitch (16, 20) arranged for each electric pole and respective phase. 4. A sensor according to claim 3, c h a r a c t e r i z e d in that the devices (16, 20) for registration of leak current include separate signal outlets (19, 22) for each electric pole and respective phase, for indicating which of the wires is taking part in any leak current. 5. A sensor according to any of preceding claims, c h a r a c t e r i z e d in that it includes several resistor bridge connections placed onto different places in the electric system of the vehicle, and connected to common registration devices. 6. A sensor according to any of the preceding claims, for > use in alternating current systems with several phases, c h a r a c t e r i z e d in that several resistor bridge connections are mutually connected with the metal element connection (12) forming the centre of a star connection.

Inventors: SVEDOFF GOERAN, SVEDOFF, GOERAN
Applicants: SVEDOFF GOERAN, VOLVO AB, AB VOLVO
Application year: 1993
Main classification: H02H3
IPC codes: G01M17, G01R19, G01R31, H02H3