SamplexPower SEC-4825BRM, Owner'S Manual

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26 | SAMLEX AMERICA INC. SAMLEX AMERICA INC. | 27
SeCtION 7 | limiting electro-Magnetic
Interference (eMI)
the chassis. As explained earlier, the noise currents are filtered to the chassis of the
unit and the chassis is connected to the Earth Ground through the Earth Ground Pin
of the AC power outlet receptacle. Avoid connecting (referencing) the DC Negative
output terminal of the power supply to the Earth Ground.
• Connect a ¼” wavelength of wire on the Negative terminal of the power supply.
Connect one end of the wire to the Negative terminal and leave the other end free.
The wavelength corresponds to the wavelength of the interfering frequency. (May
not be practical for long wave lengths).
[Formula: Wave length (Meters) = 300 / frequency in MHz]
coMBineD FiLteReD noiSe cURRentS FRoM MULtiPLe SMPS on A BRAncH
ciRcUit MAY tRiP GRoUnD FAULt ciRUit inteRRUPteR (GFci)
During malfunction or an accident, the metal chassis of a device may get energized to
unsafe voltage due to internal high voltage section coming in contact with the chassis.
If a person standing on Earth touches this energized chassis, a leakage current
proportional to the person’s skin resistance will flow through the person’s body to Earth
Ground. The leakage current through the body is higher when the skin contact resist-
ance is lower i.e. if the skin is wet or wounded. This leakage current does not return to
the power source but is dissipated in Earth Ground. A leakage current of > 5mA could
produce lethal electrical shock. Ground fault Circuit Interrupter (GfCI) is used for safety
against electrical shock due to leakage. GfCI measures the difference between the
current sent to the load and returned from the load and will trip and disconnect the
power circuit if the difference is > 5 mA. GfCIs are normally installed in AC Branch
Circuits feeding power outlets in wet areas like marine craft, RVs, spas, hot-tubs,
kitchens, washrooms, etc.
As explained earlier, Rf noise filtration circuits in SMPS generate intentional Earth Leak-
age Current. SMPS are used extensively as DC power sources in modern day electrical
/ electronic devices e.g. Audio / Video / Computing devices, power supplies, battery
chargers etc. A single GfCI outlet / GfCI breaker may be serving multiple SMPS loads
and therefore, will be sensing the sum of all the Earth Leakage Currents and, if the sum
is > 5mA after connecting this unit, the GfCI will trip. In such a case, disconnect other
SMPS based device(s) being served by this GfCI one by one till the net leakage current is
reduced to < 5mA and the GfCI does not trip. other solution is to power this unit from
a GFci outlet / GFci breaker that does not have any SMPS load or power from an outlet
that is not protected by GFci.