3.5. DC Output Connection
Warning
SHOCK HAZARD. Depending on the application, high voltages hazardous to human safety may be present on the output terminals of the MagnaDC power supply during normal operation. Disconnect AC power from the mains and open the AC input breaker before attempting any installation procedure. Ensure that the output power cables are properly labeled as to the safety hazards and that any inadvertent contact with hazardous voltages is eliminated.
DC power is wired to the ML Series MagnaDC power supply by attaching cables or bus bars to the output bus at the rear of the cabinet. The output bus design depends on the model’s maximum DC output voltage rating — the voltage in the model number, not the voltage the supply is set to operate at — and is the same on 500 kW and 1000 kW models. All connections are made through 3/8” through-holes using the 3/8” mating hardware included with the unit; if cable is used, terminate each conductor with a 3/8” ring terminal. The recommended torque for the DC connection is 240 in-lbf (27.1 Nm).
At the currents the lower-voltage models deliver, a single conductor is rarely sufficient. Where the bus provides more than one connection point per output, distribute the conductors evenly across the available points rather than stacking them on one, or connect the load bus bar directly to the output bus.
Caution
Make sure connections are tight and torqued to the recommendation above to avoid overheating of the bus bars. At the currents the ML Series delivers, a loose or partially seated connection will overheat well before any protective device responds.
Select a wire size sufficient to handle the maximum output current of the unit, whatever the intended load current or current limit setting.
Wire Size (USA) |
Equivalent Wire Size
(International)
|
Wires Per Output Terminal |
Maximum Current |
|---|---|---|---|
6 AWG |
10 mm2 |
1 |
85 Adc |
4 AWG |
25 mm2 |
1 |
110 Adc |
3 AWG |
25 mm2 |
1 |
130 Adc |
2 AWG |
35 mm2 |
1 |
150 Adc |
1 AWG |
50 mm2 |
1 |
170 Adc |
1/0 AWG |
50 mm2 |
1 |
200 Adc |
2/0 AWG |
70 mm2 |
1 |
235 Adc |
3/0 AWG |
95 mm2 |
1 |
275 Adc |
4/0 AWG |
120 mm2 |
1 |
315 Adc |
1/0 AWG |
50 mm2 |
2 |
400 Adc |
2/0 AWG |
70 mm2 |
2 |
470 Adc |
3/0 AWG |
95 mm2 |
2 |
550 Adc |
4/0 AWG |
120 mm2 |
2 |
630 Adc |
1/0 AWG |
50 mm2 |
4 |
800 Adc |
2/0 AWG |
70 mm2 |
4 |
940 Adc |
3/0 AWG |
95 mm2 |
4 |
1100 Adc |
4/0 AWG |
120 mm2 |
4 |
1260 Adc |
Notes:
Ampacities are derived from the National Electrical Code.
Values assume a 40 °C ambient and 90 °C rated wire.
Aluminum conductors carry approximately 84% of the ampacity of an equivalently sized copper conductor.
For output currents beyond the range of a single conductor, use multiple conductors in parallel or bus bars sized for the application. Magna-Power manufactures DC power cables rated to 1250 Adc, cut to length; contact your Magna-Power sales partner.
Warning
FIRE HAZARD. Select a wire size large enough to carry the ML Series MagnaDC power supply model’s maximum rated current to prevent overheating of the wires. Make sure power cable connections are secured tightly in accordance with the torque recommendation to prevent overheating of the bus bars.
After the output connections are made and verified, install the protective covers over the output bus as described in Protective Covers.
3.5.1. Grounding the DC Output
The DC output of the ML Series MagnaDC power supply is floating with respect to earth ground, and either output terminal may be earthed to establish a ground reference for the application. The maximum permissible potential from either output terminal to ground depends on the model and on whether the High Isolation Output option is fitted; refer to the DC Output Isolation entries under Output Specifications.
Warning
Do not exceed the published output isolation rating. Grounding one output terminal of a series-connected string can place the far end of the string well above the isolation rating of an individual unit. See Parallel and Series before series-connecting units.