EMC - EV

Electromagnetic Compatibility for Electric Vehicles

ISO 6469-3:2014 - EV Protection of persons against electric shock - Isolation Resistance Measurements


ISO 6469-3 Voltage Classes

Voltage Class

Maximum Working Voltage

V (d.c.)

V(a.c.) RMS

A

0<U<=60

0<U<=30

B

60<U<=1500

30<U<=1000

The values 60 V d.c./30 V a.c. (rms) are selected taking into account humid weather conditions




Isolation resistance measurements for voltage class B electric circuits

Prior to the measurement, the device under test (DUT) shall be subjected to a preconditioning period of at least 8 h at (5+/- 2) °C, followed by a conditioning period of 8 h at a temperature of (23+/- 5) °C, a humidity of 90 (+10%, -5%), and an atmospheric pressure of between 86 kPa and 106 kPa.

Alternative preconditioning and conditioning parameters may be selected provided transition across the dew point occurs shortly after the beginning of the conditioning period. The isolation resistance shall be measured during the conditioning period at a rate from which the lowest value can be determined.

 

Isolation resistance measurements of the balance of electric power systems

The test voltage shall be a d.c. voltage of at least the maximum working voltage of the voltage class B power system and be applied for a time long enough to obtain stable reading. If the system has several voltage ranges (e.g. because of boost converter) in conductively connected circuit and some of the components cannot withstand the maximum working voltage of the entire circuit, the isolation resistances of components can be measured separately by applying their own maximum working voltages after those components are disconnected.

 

The following test procedure combines the measurement of the isolation resistance of the live parts of the voltage class B balance of electric power systems against the vehicle electric chassis and against the live parts of the voltage class A balance of auxiliary electric systems.

  • Traction batteries shall be disconnected at their terminals from the power system.
  •  Electric power sources of the voltage class B power systems other than the traction batteries (fuel cell stacks, capacitors) may be disconnected at their terminals from the power system; if they remain connected, power generation shall be deactivated. 
  • Barriers and enclosures shall be included unless evaluations prove otherwise.
  • All live parts of the balance of electric power systems (voltage class B) shall be connected to each other.
  • All exposed conductive parts of the balance of electric power system shall be connected to the electric chassis.
  •  Batteries of the auxiliary electric systems (voltage class A) shall be disconnected at their terminals from the auxiliary circuits.
  •  All live parts of the balance of auxiliary electric systems (voltage class A) shall be connected to the electric chassis.

Then the test voltage shall be applied between the connected live parts of the voltage class B balance of electric power systems and the electric chassis. 

The measurements shall be performed using suitable instruments that can apply d.c. voltage (e.g. megohmmeter, provided they deliver the required test voltage). Alternatively the isolation resistance may be measured using the test procedure for the measurement of the RESS as given in ISO 6469-1 with the balance of electric power system connected to an external power source.

 Isolation resistance measurement of the voltage class B electric power sources

The measurement of the isolation resistance of an RESS, if any, shall be in accordance with ISO 6469-1. The measurement of the isolation resistance of a fuel cell stack, if any, shall be in accordance with ISO 6469-1 with the fuel cell stack in operation.

Alternatively for the measurement of the isolation resistance of a fuel cell stack, the entire mechanical structure of the fuel cell system (including the cooling system with its cooling medium) shall be considered.

Prior to the measurement, stop power generation after operation at maximum output according to the manufacturer's specification. The voltage across the fuel-cell stack power terminals shall be discharged. All cables shall be disconnected from the fuel-cell stack power terminals, and all other cables from other electric terminals of the fuel-cell stack. All cooling pipes, fuel pipes, and air pipes shall remain connected. The applied test voltage shall be at least the maximum open circuit voltage of the fuel cell stack. Apart from these specific conditions, the procedure shall be performed as given in Isolation resistance measurements of the balance of electric power systems.

 Isolation resistance measurement of entire voltage class B electric circuits

The isolation resistance of entire conductively connected voltage class B electric circuits may be measured using the test procedure for the measurement of the RESS given in ISO 6469-1 with the balance of electric power system connected to the voltage class B power sources.

Alternatively, the isolation resistance of entire conductively connected voltage class B electric circuits may be measured using an isolation resistance monitoring system, if installed on the vehicle, provided that its accuracy is sufficiently high.

In case electric or electronic switches exist in the circuit (e. g. transistors in power electronics), these switches shall be activated. If these switches cannot be activated, the relevant part of the circuit may be measured separately in accordance Isolation resistance measurements of the balance of electric power systems.

Instead of being measured, the isolation resistance of the entire conductively connected circuit may be calculated using the measured resistances of the power sources and the balance of electric power system.


Christian Rosu

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