Siemens A1 Manual De Usuario
Electromagnetic Compatibility
International English
30
MICROMASTER Applications Handbook
· The output of all inverters generates high frequency, high voltage switching
waveforms in the output cables between the motor and inverter.
· A lot of EMI occurs at high frequency. At high frequencies the shape and
length of the cable has a big effect on its impedance. Therefore short, thick,
braided leads will be most effective in grounding, and high quality screened
cable, grounded at both ends, will be needed to limit effects on signal leads.
braided leads will be most effective in grounding, and high quality screened
cable, grounded at both ends, will be needed to limit effects on signal leads.
· If equipment is badly grounded, high levels of EMI may connect from the power
part of equipment into the control connections. Similar effects can occur when
badly grounded equipment is connected together and EMI is conducted via the
control cables.
badly grounded equipment is connected together and EMI is conducted via the
control cables.
· Particular care is needed when equipment is used with low signal sensors such
as load cells and capacitive sensors.
· Conducted interference is more likely to cause problems than radiated
interference.
· The signal and control leads in any electronic system are generally low voltage,
high impedance, and are therefore particularly sensitive to the high level of EMI
present in industrial systems.
present in industrial systems.
· Switching inductive loads, such as electro-mechanical brakes, relay and
contactor coils generate severe EMI.
6.2.1
Immunity and Immunity testing
Immunity is very important as damage and nuisance tripping will cause failure and
service costs irrespective of where the fault lies. Therefore the tests carried out
during product development are quite severe, and represent conditions
encountered in industry.
service costs irrespective of where the fault lies. Therefore the tests carried out
during product development are quite severe, and represent conditions
encountered in industry.
Tests include:
· Electrostatic Discharge testing of all exposed surfaces, terminal and buttons
using high voltage discharge gun. This simulates the effect of discharge from
a human body electrostatically charged from a carpet for example.
a human body electrostatically charged from a carpet for example.
· High voltage very high frequency discharges capacitively coupled into the
control lines. This simulates the interference that couples from power
switching (contactors etc.) into control leads.
switching (contactors etc.) into control leads.
· Similar discharges directly into the supply leads, line to line and line to ground.
This simulates conducted interference from arcing contacts in other equipment.
· High energy, lower frequency interference in the supply leads, line to line and
line to earth. This simulates lightning strike interference and similar supply
disturbance.
disturbance.