Document ID: chunk:federal_register_of_legislation:F2025L00028:reg:3:p8
Version: federal_register_of_legislation:F2025L00028
Segment Type: reg
Provision Reference: reg 3 (pt 8/11)
Character Range: 140857–144181

resistance tester that meets the specification that follows:

                   (i) Resistance tester: Measurement current at least 0.2 A;

                   (ii) Resolution: 0.01 Ω or less;

                   (iii) The resistance R shall be less than 0.1 Ω.

                  (b) Test method using DC power supply, voltmeter and ammeter.

                   The DC power supply, voltmeter and ammeter are connected to the measuring points (Typically, electrical chassis and electro conductive enclosure/electrical protection barrier).

                  The voltage of the DC power supply is adjusted so that the current flow becomes at least 0.2 A.

                  The current "I" and the voltage "U" are measured.

                  The resistance "R" is calculated according to the following formula:

                  R = U / I

                  The resistance R shall be less than 0.1 Ω.

                Note: If lead wires are used for voltage and current measurement, each lead wire shall be independently connected to the electrical protection barrier/enclosure/electrical chassis. Terminal can be common for voltage measurement and current measurement.

                Example of the test method using DC power supply, voltmeter and ammeter is shown below.

              Figure 4
       Example of test method using DC power supply

              5. Isolation resistance

              5.1. General.

               The isolation resistance for each high voltage bus of the vehicle is measured or shall be determined by calculating the measurement values of each part or component unit of a high voltage bus.

               All measurements for calculating voltage(s) and electrical isolation are made after a minimum of 10 s after the impact.

              5.2. Measurement method.

               The isolation resistance measurement is conducted by selecting an appropriate measurement method from among those listed in paragraphs 5.2.1. to 5.2.2. of this Annex, depending on the electrical charge of the live parts or the isolation resistance.

               The range of the electrical circuit to be measured is clarified in advance, using electrical circuit diagrams. If the high voltage buses are conductively isolated from each other, isolation resistance shall be measured for each electrical circuit.

               Moreover, modifications necessary for measuring the isolation resistance may be carried out, such as removal of the cover in order to reach the live parts, drawing of measurement lines and change in software.

               In cases where the measured values are not stable due to the operation of the on-board isolation resistance monitoring system, necessary modifications for conducting the measurement may be carried out by stopping the operation of the device concerned or by removing it. Furthermore, when the device is removed, a set of drawings will be used to prove that the isolation resistance between the live parts and the electrical chassis remains unchanged.

               These modifications shall not influence the test results.

               Utmost care shall be exercised to avoid short circuit and electric shock since this confirmation might require direct operations of the high-voltage circuit.

              5.2.1. Measurement method using DC