Ametek Sorensen DLM-E, Operation Manual

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DLM-E 3kW & 4kW Series Power Supplies Installation
M362000-01 Rev E 2-11
2.8.1 Load Conductor Ratings
As a minimum, load wiring must have a current capacity greater than the output current rating of
the power supply. This ensures that the wiring will not be damaged even if the load is shorted.
The table below shows the maximum current rating, based on 450 amps per square centimeter,
for various gauges of wire rated for 105 degrees C operation.
Operation at the maximum current rating results in approximately a 30–degree temperature rise
for a wire operating in free air. Where load wiring must operate in areas with elevated ambient
temperatures or bundled with other wiring, larger gauges or higher temperature–rated wiring
should be used.
To overcome impedance and coupling effects, which can degrade the power supply
performance, the use of leads of the largest gauge and shortest length possible is
recommended.
AWG Maximum Current AWG Maximum Current
16 7 1 209
14 11 1/0 270
12 18 2/0 330
10 23 3/0 350
8 39 4/0 408
6 67 250 MCM 425
4 106 300 MCM 480
2 170
2.8.2 Noise and Impedance Effects
To minimize noise pickup or radiation from load circuits, load wires and remote sense wires
should be twisted-pair with minimum lead length. Shielding of the sense leads may be
necessary in high noise environments. Even if noise is not a concern, the load and remote
sense wires should be twisted-pairs to reduce coupling between them, which could impact the
stability of the power supply. If connectors are utilized for the power and sense leads, be
careful not to introduce coupling between the leads. Ensure that the connector terminals for the
sense leads are in adjacent locations, and minimize the physical loop area of the untwisted
portions. Ideally, the sense leads should be separated from the power leads and should have
their own connector.
Twisting the load wires provides an additional benefit in reducing the parasitic inductance of the
cable. This improves the dynamic response characteristics at the load by maintaining a low
source impedance at high frequencies. Also, with long load wires, the resultant inductance and
resistance could produce high frequency voltage spikes at the load due to current variations in
the load itself. The impedance introduced between the output of the power supply and the load
could make the ripple/noise at the load worse than the specifications of the power supply (which
are valid when measured at the rear panel bus bars). Additional filtering with bypass capacitors
at the load terminals may be required to bypass the high frequency load currents.