CN109444549B - Rapid detection method for vehicle body insulation - Google Patents
Rapid detection method for vehicle body insulation Download PDFInfo
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- CN109444549B CN109444549B CN201811242110.3A CN201811242110A CN109444549B CN 109444549 B CN109444549 B CN 109444549B CN 201811242110 A CN201811242110 A CN 201811242110A CN 109444549 B CN109444549 B CN 109444549B
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R27/00—Arrangements for measuring resistance, reactance, impedance, or electric characteristics derived therefrom
- G01R27/02—Measuring real or complex resistance, reactance, impedance, or other two-pole characteristics derived therefrom, e.g. time constant
- G01R27/08—Measuring resistance by measuring both voltage and current
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Abstract
The invention discloses a quick detection circuit and a method for vehicle body insulation, which are characterized in that the voltage at two ends of a first capacitor is detected, after the first capacitor is completely discharged, a first switch is closed to detect the voltage at two ends of a first resistor, the current passing through the first resistor is calculated, and the voltage at two ends of a fourth resistor, a third resistor, a fifth resistor and the parallel resistance value of the fourth resistor in parallel connection are calculated; when the voltage value of the first resistor is smaller than the set voltage value, closing the second switch, re-detecting the voltages at the two ends of the first resistor, calculating the current of the first resistor and the voltage at the two ends of the fourth resistor, and calculating the parallel resistance value of the fourth resistor and the fifth resistor; when the parallel resistance value exceeds the set resistance value, the first relay switch and the second relay switch are allowed to be closed; when the parallel resistance value does not exceed the set resistance value, the first relay switch and the second relay switch are forbidden to be closed; the electric automobile has the advantages that before the electric automobile is started, the insulation detection can be realized on the automobile body, and the safety accidents caused by the electric leakage of the electric elements in the automobile can be effectively avoided.
Description
Technical Field
The invention relates to the field of insulation detection, in particular to a method for quickly detecting insulation of a vehicle body.
Background
The electric automobile is an electromechanical integration product, and parts such as a power battery, a motor, an auxiliary charging device and the like contained in the electric automobile need to consider the problem of high-voltage insulation. Meanwhile, the environment conditions for the electric automobile are severe, such as high-strength bumping vibration, acid-base gas corrosion and temperature change, and the electric automobile part insulating material is aged or even damaged in the environment, so that electric leakage is caused. The voltage value of the power battery pack of the electric automobile is more than 300 volts and far exceeds the human body safety voltage of 36 volts, so that once electric leakage occurs and the electric leakage is not detected in time, life danger is caused to a driver or passengers. Insulation detection is mainly carried out insulation judgment through the insulation resistance of an object to be detected, and the existing measurement mode of the insulation resistance comprises the following steps: an alternating current signal injection method and an unbalanced bridge method; the alternating current signal injection method is influenced by the load of a power battery in the electric automobile, and the measurement of the alternating current signal injection method is inaccurate due to the instability of the load after the power battery works; the unbalanced bridge measurement method needs to arrange a high-voltage loop to pressurize a component to be measured so as to measure.
Disclosure of Invention
The invention aims to solve the technical problem of providing a rapid detection method for vehicle body insulation, which realizes rapid measurement by applying a direct-current power supply with a lower voltage value and has higher reliability.
The technical scheme adopted by the invention for solving the technical problems is as follows: a method for quickly detecting the insulation of a vehicle body comprises the following steps:
step 3, calculating a voltage value of two ends of the fourth resistor to be Ursio 1 by applying an excitation power supply with the voltage of Uax and the detected voltage of two ends of the first resistor;
step 4, when the voltage value at the two ends of the first resistor detected by the voltage detection module is not less than the set voltage value, calculating a first parallel resistor in which the third resistor, the fifth resistor and the fourth resistor are connected in parallel according to the current value of the first resistor obtained in the step 2 and the voltage value at the two ends of the fourth resistor obtained in the step 3, wherein the first parallel resistor is Rplaclel;
step 5, when the voltage value at the two ends of the first resistor detected by the voltage detection module is smaller than the set voltage value, closing the second switch, and detecting the voltage value U1 ' at the two ends of the first resistor again at the moment to calculate a current value I1 ' passing through the first resistor and a voltage value uri 1 ' at the two ends of the fourth resistor;
step 6, calculating a second parallel resistor formed by connecting the fourth resistor and the fifth resistor in parallel through the current value I1 ' flowing through the first resistor, the voltage value Ursio 1 ' at the two ends of the fourth resistor and the resistance value R2x of the second resistor obtained in the step 5, wherein the second parallel resistor is Rparallell ';
step 7, when the first parallel resistance value in the step 4 or the second parallel resistance value in the step 6 exceeds a set resistance value, the first switch is switched off, and at the moment, a control system in the electric vehicle allows the first relay switch and the second relay switch to be closed; and when the first parallel resistance value in the step 4 or the second parallel resistance value in the step 6 does not exceed the set resistance value, the control system in the electric vehicle does not allow the first relay switch and the second relay switch to be closed.
Preferably, the voltage of the excitation power supply in step 3 is 12V, and the set voltage value in step 5 is 0.5 volt.
Preferably, the calculation formula of the current value I1 passing through the first resistor in step 2 is: i1= U1/R1 x.
Preferably, the calculation formula of the voltage value uri 1 across the fourth resistor in step 3 is: ursio 1= Uax-U1.
Preferably, in step 4, a calculation formula of the parallel resistance value Rparallel of the parallel connection of the third resistor, the fifth resistor and the fourth resistor is as follows: rparallel = urino 1/I1= (Uax-U1) × R1 x/U1.
Preferably, the calculation formula of the current value I1' passing through the first resistor in step 5 is: i1 '= U1'/R1 x;
the voltage value uri 1' across the fourth resistor is calculated as: ursio 1 '= Uax-U1'.
Preferably, in step 6, the parallel resistance value Rparallel' of the fourth resistor and the fifth resistor is calculated according to the following formula:
Rparallel’=R1x*R2x*（Ua-U1’）/（R2x*U1’-R1x*Uax+R1x*U1’）。
preferably, the resistance value of the third resistor is 1K ohm.
Preferably, the set resistance value in step 7 is 30K ohms.
Compared with the prior art, the invention has the advantages that the insulation detection can be realized on the automobile body before the electric automobile is started, the safety accident caused by the electric leakage of the electric elements in the automobile is effectively avoided, and only the 12V direct current excitation power supply is applied during the insulation detection on the automobile body without applying larger voltage; the insulation of the automobile body is detected before the electric automobile is started, so that the influence of factors such as noise after the electric automobile is started, a power battery of the electric automobile and the like is avoided, the insulation resistance value of the automobile body can be accurately measured, and the insulation of the automobile body can be accurately judged; meanwhile, the circuit structure is simple, quick response can be realized, the detection time of the insulation resistance value of the vehicle body is greatly shortened, and quick detection of the insulation resistance value is realized.
Drawings
FIG. 1 is a circuit diagram of the present invention;
FIG. 2 is a state diagram of the circuit diagram of the present invention with only the first switch closed;
fig. 3 is a state diagram of the circuit connection diagram of the present invention when the first switch and the second switch are closed.
Detailed Description
The invention is described in further detail below with reference to the accompanying examples.
A method for quickly detecting the insulation of a vehicle body comprises the following steps: step 1, constructing a rapid detection circuit as shown in the figure, which includes a power battery V, a first relay switch SW1, a second relay switch SW2, a first capacitor C1, a second capacitor Cy1, a third capacitor Cy2, a first resistor R1, a second resistor R2, a third resistor R3, a fourth resistor Riso1, a fifth resistor Riso2 and an excitation power Ua, wherein an anode of the power battery is connected with one end of the first relay switch SW1, a cathode of the power battery V is connected with one end of the second relay switch SW2, the other end of the first relay SW1 is electrically connected with one end of the first capacitor C1, one end of the second capacitor Cy1, one end of the third resistor R3, one end of the fourth resistor Riso1, one end of the first switch S1, the other end of the second relay switch SW2 is electrically connected with one end of the third capacitor C2, one end of the fifth resistor R2, one end of the first capacitor Riso1, one end of the first capacitor R867, and the other end of the first resistor S8658, the second relay switch S1, the other end of the first relay switch S8672, the second relay switch S1 and the second, One end of each first resistor R1 is electrically connected, the other end of each second switch S2 is electrically connected with one end of each second resistor R2, the other end of each first resistor R1 is connected with the positive electrode of the excitation power supply Ua, and the other end of each second resistor R2, the other end of each second capacitor Cy1, the other end of each third capacitor Cy2, the other end of each fourth resistor Riso1 and the other end of each fifth resistor Riso2 are electrically connected with the negative electrode of the excitation power supply Ua;
step 4, when the voltage value at the two ends of the first resistor detected by the voltage detection module is not less than the set voltage value of 0.5 volt, calculating a first parallel resistor formed by connecting the third resistor R3, the fifth resistor Riso2 and the fourth resistor Riso1 in parallel according to the current value of the first resistor R1 obtained in the step 2 and the voltage value at the two ends of the fourth resistor Riso1 obtained in the step 3, wherein the first parallel resistor is Rplacell;
step 5, when the voltage value at the two ends of the first resistor R1 detected by the voltage detection module is smaller than the set voltage value by 0.5 volt, closing the second switch S2, and re-detecting the voltage value U1 ' at the two ends of the first resistor R1 at this time, and calculating to obtain a current value I1 ' passing through the first resistor R1 and a voltage value uri 1 ' at the two ends of the fourth resistor Riso1 at this time;
step 6, calculating a second parallel resistor formed by connecting the fourth resistor Riso1 and the fifth resistor Riso2 in parallel through the current value I1 ' flowing through the first resistor R1, the voltage value Ursio 1 ' at the two ends of the fourth resistor R1 and the resistance value R2x of the second resistor R2 obtained in the step 5, wherein the second parallel resistor is Rparallell ';
step 7, when the first parallel resistance value in the step 4 or the second parallel resistance value in the step 6 exceeds the set resistance value, namely 30K ohms, the first switch S1 is opened, and at the moment, the control system in the electric vehicle allows the first relay switch SW1 and the second relay switch SW2 to be closed; when the first parallel resistance value in step 4 or the second parallel resistance value in step 6 does not exceed the set resistance value, that is, 30K ohms, the control system in the electric vehicle does not allow the first relay switch SW1 and the second relay switch SW2 to be closed.
Further, the excitation power source Ua in step 3 is a dc power source with a voltage of 12V.
Further, the calculation formula of the current value I1 passing through the first resistor R1 in step 2 is: i1= U1/R1 x.
Further, the voltage value uri 1 across the fourth resistor Riso1 in step 3 is calculated as: ursio 1= Uax-U1.
Further, in step 4, the calculation formula of the parallel resistance Rparallel of the parallel connection of the third resistor R3, the fifth resistor Riso2 and the fourth resistor Riso1 is as follows: rparallel = urino 1/I1= (Uax-U1) × R1 x/U1.
Further, the calculation formula of the current value I1' passing through the first resistor R1 in step 5 is: i1 '= U1'/R1 x;
the voltage value uri 1' across the fourth resistor Riso1 is calculated as: ursio 1 '= Ua-U1'.
Further, the parallel resistance value Rparallel' of the fourth resistor Riso2 and the fifth resistor Riso2 in step 6 is calculated by the following formula: rparallell ' = R1x × R2x ' (Uax-U1 ')/(R2 x × U1 ' -R1x × Uax + R1x × U1 ').
Further, the resistance value of the third resistor R3 is 1K ohm.
In light of the above description of the preferred embodiments of the invention, it is to be understood that many changes and modifications may be made by one skilled in the art without departing from the spirit and scope of the invention.
Claims (9)
1. A method for rapidly detecting the insulation of a vehicle body is characterized by comprising the following steps:
step 1, constructing a rapid detection circuit, wherein the rapid detection circuit comprises a power battery, a first relay switch, a second relay switch, a first capacitor, a second capacitor, a third capacitor, a first resistor, a second resistor, a third resistor, a fourth resistor, a fifth resistor and an excitation power supply, the anode of the power battery is connected with one end of the first relay switch, the other end of the power battery is connected with one end of the second relay switch, the other end of the first relay is electrically connected with one end of the first capacitor, one end of the second capacitor, one end of the third resistor, one end of the fourth resistor and one end of the first switch, the other end of the second relay is electrically connected with one end of the third capacitor, one end of the fifth resistor, the other end of the first capacitor and the other end of the third resistor, the other end of the first switch is electrically connected with one end of the second switch and one end of the first resistor, the other end of the second switch is electrically connected with one end of a second resistor, the other end of the first resistor is connected with the anode of the excitation power supply, and the other end of the second resistor, the other end of the second capacitor, the other end of the third capacitor, the other end of the fourth resistor and the other end of the fifth resistor are electrically connected with the cathode of the excitation power supply;
step 2, when the electric automobile is started and powered on, before the first relay switch and the second relay switch are closed, the voltage at two ends of a first capacitor on the automobile body is detected, after the first capacitor is completely discharged, the first switch is closed, the voltage at two ends of a first resistor with the resistance value of R1x is detected to be U1 through a voltage detection module, and the current value passing through the first resistor is calculated to be I1;
step 3, calculating a voltage value of two ends of the fourth resistor to be Ursio 1 by applying an excitation power supply with the voltage of Uax and the detected voltage of two ends of the first resistor;
step 4, when the voltage value at the two ends of the first resistor detected by the voltage detection module is not less than the set voltage value, calculating a first parallel resistor in which the third resistor, the fifth resistor and the fourth resistor are connected in parallel according to the current value of the first resistor obtained in the step 2 and the voltage value at the two ends of the fourth resistor obtained in the step 3, wherein the first parallel resistor is Rplaclel;
step 5, when the voltage value at the two ends of the first resistor detected by the voltage detection module is smaller than the set voltage value, closing the second switch, and detecting the voltage value U1 ' at the two ends of the first resistor again at the moment to calculate a current value I1 ' passing through the first resistor and a voltage value uri 1 ' at the two ends of the fourth resistor;
step 6, calculating a second parallel resistor formed by connecting the fourth resistor and the fifth resistor in parallel through the current value I1 ' flowing through the first resistor, the voltage value Ursio 1 ' at the two ends of the fourth resistor and the resistance value R2x of the second resistor obtained in the step 5, wherein the second parallel resistor is Rparallell ';
step 7, when the first parallel resistance value in the step 4 or the second parallel resistance value in the step 6 exceeds a set resistance value, the first switch is switched off, and at the moment, a control system in the electric vehicle allows the first relay switch and the second relay switch to be closed; and when the first parallel resistance value in the step 4 or the second parallel resistance value in the step 6 does not exceed the set resistance value, the control system in the electric vehicle does not allow the first relay switch and the second relay switch to be closed.
2. The method for rapidly detecting the insulation of the vehicle body according to claim 1, wherein the voltage of the excitation power supply in the step 3 is 12V, and the set voltage value in the step 5 is 0.5V.
3. The method for rapidly detecting the insulation of the vehicle body according to claim 1, wherein the calculation formula of the current value I1 passing through the first resistor in the step 2 is as follows: i1= U1/R1 x.
4. The method for rapidly detecting the insulation of the vehicle body according to claim 1, wherein the voltage value Ursio 1 at the two ends of the fourth resistor in the step 3 is calculated by the formula: ursio 1= Uax-U1.
5. The method for rapidly detecting the insulation of the vehicle body according to claim 1, wherein in the step 4, a calculation formula of a parallel resistance value Rparallell of a third resistor, a fifth resistor and a fourth resistor connected in parallel is as follows: rparallel = urino 1/I1= (Uax-U1) × R1 x/U1.
6. The method for rapidly detecting the insulation of the vehicle body according to claim 1, wherein the current value I1' passing through the first resistor in the step 5 is calculated by the formula: i1 '= U1'/R1 x;
the voltage value uri 1' across the fourth resistor is calculated as: ursio 1 '= Uax-U1'.
7. The method for rapidly detecting the insulation of the vehicle body as claimed in claim 1, wherein the calculation formula of the parallel resistance value Rparallel' of the fourth resistor and the fifth resistor in the step 6 is as follows:
Rparallel’=R1x*R2x*（Ua-U1’）/（R2x*U1’-R1x*Uax+R1x*U1’）。
8. the method as claimed in claim 1, wherein the third resistor has a resistance of 1K ohms.
9. The method for rapidly detecting the insulation of the vehicle body according to claim 1, wherein the resistance value set in the step 7 is 30K ohms.
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