Document ID: chunk:federal_register_of_legislation:F2023L01526:body:0:p38
Version: federal_register_of_legislation:F2023L01526
Segment Type: other
Provision Reference: 
Character Range: 107711–110777

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 of the high-voltage circuit.

       2.1. Measurement method using DC voltage from external sources

       2.1.1. Measurement instrument

        An isolation resistance test instrument capable of applying a DC voltage higher than the working voltage of the high voltage bus shall be used.

       2.1.2. Measurement method

        An isolation resistance test instrument shall be connected between the live parts and the electrical chassis. Then, the isolation resistance shall be measured by applying a DC voltage at least half of the working voltage of the high voltage bus.

        If the system has several voltage ranges (e.g. because of boost converter) in galvanically connected circuit and some of the components cannot withstand the working voltage of the entire circuit, the isolation resistance between those components and the electrical chassis can be measured separately by applying at least half of their own working voltage with those component disconnected.

       2.2. Measurement method using the vehicle's own REESS as DC voltage source

       2.2.1. Test vehicle conditions

        The high voltage-bus shall be energized by the vehicle's own REESS and/or energy conversion system and the voltage level of the REESS and/or energy conversion system throughout the test shall be at least the nominal operating voltage as specified by the vehicle manufacturer.

       2.2.2. Measurement instrument

        The voltmeter used in this test shall measure DC values and shall have an internal resistance of at least 10 MΩ.

       2.2.3. Measurement method

       2.2.3.1. First step

        The voltage is measured as shown in Figure 1 and the high voltage bus voltage (Ub) is recorded. Ub shall be equal to or greater than the nominal operating voltage of the REESS and/or energy conversion system as specified by the vehicle manufacturer.

    Figure 1
    Measurement of Ub, U1, U2

       2.2.3.2. Second step

        Measure and record the voltage (U1) between the negative side of the high voltage bus and the electrical chassis (see Figure 1).

       2.2.3.3. Third step

        Measure and record the voltage (U2) between the positive side of the high voltage bus and the electrical chassis (see Figure 1).

       2.2.3.4. Fourth step

        If U1 is greater than or equal to U2, insert a standard known resistance (Ro) between the negative side of the high voltage bus and the electrical chassis. With Ro installed, measure the voltage (U1') between the negative side of the high voltage bus and the electrical chassis (see Figure 2).

        Calculate the electrical isolation (Ri) according to the following formula:

        Ri = Ro*Ub*(1/U1' – 1/U1)

    Figure 2
    Measurement of U1'

        If U2 is greater than U1,