EMC and petrol engine interference

For more than a decade now, Australia has had mandatory regulations in place for electromagnetic compatibility (EMC) for the majority of electric and electronic devices.

The government body responsible for managing the EMC framework in Australia is the Australian Communications and Media Authority (ACMA). This regulatory framework encompasses the vast majority of electrical and electronic equipment.

Compliance with the Australian and New Zealand EMC regulations is indicated by the application of the C-tick logo to the product.

These regulations have been imposed to protect radio communications, including mobile telephones, two-way radio, and free-to-air radio and television services from interference, which can occur due to unintentional emissions emanating from various electric or electronic devices.

Vehicles and equipment with internal combustion engines are a potential source of RF interference to radio communications.

Petrol engines produce significant RF emissions from their ignition systems. Diesel engines do not have an ignition system and as such their RF emission profile is significantly lower, with emissions emanating only from electronic control circuitry.

DC electric motors can also produce significant RF noise from the intermittent connection of the brushes during rotation of the commutator.

The relevant EMC standard for such products is AS/NZS CISPR 12. The scope of AS/NZS CISPR 12 includes vehicles and boats which are powered from internal combustion engines or electric motors, as well as devices powered from internal combustion engines, examples of which are shown in the table.

Excluded from the scope of AS/NZS CISPR 12 are aircraft, traction systems (for trains, trams and electric trolley buses), partial vehicles and boats more than 15 m long.

The ACMA has also exempted vehicles or machines that are supplied by a member of the Federal Chamber of Automotive Industries (FCAI), the Truck Industry Council (TIC), the Construction and Mining Equipment Industry Group (CMEIG) or the Tractor and Machinery Association (TMA), provided they comply with all relevant EMC emission standards applicable to their respective vehicle or unit.

The test procedures detailed in AS/NZS CISPR 12 require EMC measurements performed on vehicles and boats to be carried out on both the left and right sides, in line with the engine position. These measurements are performed with the ignition on (engine off) and then repeated with the engine running.

Single-cylinder engines are operated at 2500 rpm, while multi-cylinder engines are operated at 1500 rpm. Vehicles and boats fitted with an electric motor are configured in a free-wheeling or unloaded condition while simulating an operating speed of 40 km/h (or at maximum speed, if that is less than 40 km/h).

If a vehicle can be connected to the mains electricity supply (such as for charging batteries of an electric vehicle), then other EMC standards may also be applicable.

Measurements on equipment or devices are performed in the direction of maximum emissions and, for handheld equipment, in three orientations as is practical. RF emissions are measured at idle and again at normal/full load. If applicable, ignition on (engine off) and engine running measurements are also required.

Aftermarket devices installed into a vehicle do not fall within the scope of AS/NZS CISPR 12 and are required to comply with a separate EMC standard relevant to the specific aftermarket product. Some examples are shown here:

• Audio entertaining system AS/NZS CISPR 13;
• GPS receiver AS/NZS CISPR 22;
• Refrigeration unit AS/NZS CISPR 14.1;
• DC to DC inverter AS/NZS CISPR 11.

All suppliers marketing electric or electronic products to the Australian or New Zealand market, including vehicles, boats or devices fitted with an internal combustion engine, must comply with mandatory C-tick requirements.

An EMC test report is required for each product as evidence of compliance and forms part of the Compliance Folder, which must be held at the supplier’s premises. The C-tick logo and supplier number must also be affixed to each product to indicate compliance with the applicable EMC standard.