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83
-
507
-
013 Rev. D
20
3.9.4
Noise and I
m
pedance 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 no
ise env
i-
ronments. 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 powe
r 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 fr
e-
quency voltage spikes at the load and the output of the 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 lo
ads
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. C
onnect 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 suppre
s-
sor across the output to protect the power supply. The breakd
own 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
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
Hazardous voltages may exist at the outputs and the load conne
c
tions
when using a power supply with a rated output greater than 40V. T
o
protect personnel against accidental contact with hazardous vol
t
ages,
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 powe
r supply.
CAUTION
Ensure that the load wiring mounting hardware does not short the ou
t
put
terminals. Heavy connecting cables must have some form of strain relief
to prevent loosening the connections or bending the bus
-
bars.