john aitken, aitken & partners consulting engineers - electromagnetic compatibility (emc) for...

EMC forSafety

John Aitken

Aitken & Partners

Electromagnetic Compatibility

Ability to function satisfactorily in its electromagnetic environment

Electromagnetic Compatibility

Ability to function satisfactorily in its electromagnetic environment

without introducing

intolerable electromagnetic disturbances to

anything in that environment.

IEC 600500-826

“… must be designed, built and

maintained with regard to EMC in

order that they operate safely

throughout their operational life.

Safety

Freedom from

unacceptable

risk of harm.

EN 50126

unacceptable

risk of harm

Disturbances

intolerable

disturbances

conducted

disturbance

Midya

Midya

inductive

disturbance

Armstrong

Hill

radiated

disturbance

EN 50238

Simple

concept

✗

Don’t let unwanted energy out of component

Don’t let unwanted energy into component

Minimise unwanted energy

Make systems compatible

✗

safety

margin

Standards

• EN 50121 – Railway System

• EN 50238 – Train Detection

• EN 50500 – Effects on People

• ARPANSA No 3 – Australian Law

Standards

• Precise tests of one thing at a time

• Repeatable results

• Laboratory conditions

• Nothing like a railway!

EN 50121

• Part 1 – General

• Part 2 – Emission of the entire railway

• Part 3 - 1 Rolling Stock – Train

• Part 3 – 2 Rolling Stock – Components

• Part 4 – Signalling and Telecommunications

• Part 5 – Fixed Power.

Immunity Standards

Immunity Standards

Radiated Emissions

Conducted Emissions

ECP – Right side failure

Sudden, unexplained emergency brake application

Often at the same place – but not always

Many Observations

• Only with ECP

• Not always, but usually in electrified area

• Usually associated with dynamic brake

• More often on the steep grades on the mountain range

• Happens sometimes when you cut off power

• Very frequently at the port.

The cause – traction harmonics

• Always there:

– Absorbed into traction circuit under load

– Distributed on overhead system when in dynamic brake or stationary

Finding the problem

• The problem was found – a design issue in a power supply.

• The balanced line for ECP was not balanced at all frequencies because the power supply designer put in a component to pass an EMC test. The component shunted unwanted frequencies from the power supply to ground.

Finding the problem

• The problem was found – a design issue in a power supply.

• The balanced line for ECP was not balanced at all frequencies because the power supply designer put in a component to pass an EMC test. The component shunted unwanted frequencies from the power supply to ground.

Good design

• Standards prescribe tests to identify known problems

• The tests cover a limited number of circumstances

• Tests are done sequentially.

• Real life is not like that. Things happen.• They don’t check the standards first!• Careful, consistent design is essential.

Thank you