Document ID: chunk:federal_register_of_legislation:F2023L01529:body:0:p29
Version: federal_register_of_legislation:F2023L01529
Segment Type: other
Provision Reference: 
Character Range: 81103–84076

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 (Vb) is recorded. Vb 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 Vb, V1, V2

        Measure and record the voltage (V1) 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 (V2) between the positive side of the high voltage bus and the electrical chassis (see Figure 1).

       2.2.3.4. Fourth step

        If V1 is greater than or equal to V2, 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 (V1') 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*(Vb/V1' – Vb/V1) or Ri = Ro*Vb*(1/V1' – 1/V1)

       Figure 2
       Measurement of V1'

       If V2 is greater than V1, insert a standard known resistance (Ro) between the positive side of the high voltage bus and the electrical chassis. With Ro installed, measure the voltage (V2') between the positive side of the high voltage bus and the electrical chassis (see Figure 3). Calculate the electrical isolation (Ri) according to the formula shown. Divide this electrical isolation value (in Ω) by the nominal operating voltage of the high voltage bus (in volts).

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

       Ri = Ro*(Vb/V2' – Vb/V2) or Ri = Ro*Vb*(1/V2' – 1/V2)

       Figure 3
       Measurement of V2'

       2.2.3.5. Fifth step

        The electrical isolation value Ri (in Ω) divided by the working voltage of the high voltage bus (in volts) results in the isolation resistance (in Ω/V).