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3.9.4 Noise and Impedance Effects
To minimize the noise pickup or radiation, the load wires and remote sense wires should be twisted-
pairs to the shortest possible length. Shielding of sense leads may be necessary in high noise
environments. Where shielding is used, connect the shield to the chassis via a rear panel Ground
screw. Even if noise is not a concern, the load and remote sense wires should be twisted-pairs to
reduce coupling, which might impact the stability of power supply. The sense leads should be
separated from the power leads.
Twisting the load wires reduces the parasitic inductance of the cable which could produce high
frequency voltage spikes at the load and the output of power supply, because of current variation in
the load itself.
The impedance introduced between the power supply output and the load could make the ripple
and noise at the load worse than the noise at the power supply rear panel output. Additional filtering
with bypass capacitors at the load terminals may be required to bypass the high frequency load
current.
3.9.5 Inductive loads
Inductive loads can produce voltage spikes that may be harmful to the power supply. A diode should
be connected across the output. The diode voltage and current rating should be greater than the
power supply maximum output voltage and current rating. Connect the cathode to the positive
output and the anode to the negative output of the power supply.
Where positive load transients such as back EMF from a motor may occur, connect a surge
suppressor across the output to protect the power supply. The breakdown voltage rating of the
suppressor must be approximately 10% higher than the maximum output voltage of the power
supply.
3.9.6 Making the load connections
Hazardous voltages may exist at the outputs and the load connections
when using a power supply with a rated output greater than 40V. To
protect personnel against accidental contact with hazardous voltages,
ensure that the load and its connections have no accessible live parts.
Ensure that the load wiring insulation rating is greater than or equal to
the maximum output voltage of the power supply.
Ensure that the load wiring mounting hardware does not short the output
terminals. Heavy connecting cables must have some form of strain relief
to prevent loosening the connections or bending the bus-bars.
6V to 60V Models
Refer to Fig.3-5 for connection of the load wires to the power supply bus-bars and to Fig.3-6
for mounting the bus-bars shield to the chassis.
WARNING
CAUTION
20
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