Document ID: chunk:federal_register_of_legislation:F2023L01526:body:0:p37
Version: federal_register_of_legislation:F2023L01526
Segment Type: other
Provision Reference: 
Character Range: 104889–108003

R shall be less than 0.1 Ω.

       2. Test method using DC power supply, voltmeter and ammeter.

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

Figure 1
Example of Test Method using DC Power Supply

       2.1. Test Procedure.

        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.

Annex 5A

Isolation resistance measurement method for vehicle based tests

       1. General

        The isolation resistance for each high voltage bus of the vehicle shall be measured or shall be determined by calculation using measurement values from each part or component unit of a high voltage bus (hereinafter referred to as the "divided measurement").

       2. Measurement method

        The isolation resistance measurement shall be conducted by selecting an appropriate measurement method from among those listed in paragraphs 2.1. through 2.2. of this annex, depending on the electrical charge of the live parts or the isolation resistance, etc.

        Megohmmeter or oscilloscope measurements are appropriate alternatives to the procedure described below for measuring isolation resistance. In this case, it may be necessary to deactivate the on-board isolation resistance monitoring system.

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

        Moreover, modification 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, change in software, etc.

        In cases where the measured values are not stable due to the operation of the on-board isolation resistance monitoring system, necessary modification for conducting the measurement may be carried out by stopping of the operation of the device concerned or 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 as to shor t circuit and electric shock since this confirmation might require direct operations