For the majority of DC/DC converter applications
in the telecommunications and
datacommunications equipment, the applicable
safety standards are UL1950 (and its
Canadian equivalent C22.2 No. 950-95) for
North America and EN60950 for Europe.
Both are titled ?Standards for Safety of
Information Technology Equipment (ITE),
Including Electrical Business Equipment,?.
2- UL1950/EN60950 Safety
Principle
These safety standards address construction
issues and are intended to prevent injury to
equipment operators and service personnel as
well as other forms of damage caused by :
- Electric shock,
- Energy hazards,
- Fire,
- Mechanical and heat hazards,
- Radiation Hazards,
- Chemical Hazards.
Electric shock is due to current passing through
the human body. Currents of the order of a
milliampere can cause a reaction in persons in
good health and may cause indirect danger
due to involuntary reaction. Higher currents
can have more damaging effects.
Voltages up to about 40Vac peak, or 60Vdc,
are not generally regarded as dangerous under
1- General
dry conditions, but parts which have to be
touched or handled should be at earth potential
or properly insulated. It is normal to provide
two levels of protection for operators to prevent
electric shock.
Energy Hazards can be caused by arcing or
ejection of molten metal when adjacent poles
of high current supplies or high capacitance
circuits are short-circuited. Protection is made
by separation, by shielding or by using safety
interlocks.
Fire risks may result from overloads,
component failure, insulation breakdown or
loose connections. Fires should not spread
beyond the immediate vicinity of the source of
the fire or cause damage to the surroundings
of the equipment.
Mechanical and heat hazards should be
prevented by providing adequate stability, by
avoiding sharp edges and points or by
restricting access to dangerous parts.
Radiation Hazards encountered can be sonic,
radio frequency, infra-red, high intensity visible
and coherent light, ionising, etc.
Requirements are necessary to keep person
exposures to acceptable levels.
Chemical Hazards through contact with
chemicals, their vapours and fumes are required
to be limited under normal and abnormal conditions.