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For proper regulation the load wires should be large enough to limit the voltage drop to no more than 0.5 volts per lead. Table 3-2 lists resistivity for various wire sizes and the maximum lengths that may be used to limit voltage drop to 0.5 volts for various currents. Lengths listed are the sum of the lengths of the (+ ) and ( - ) load wires. Lengths are given in meters and (feet). To determine maximum lengths (in meters or feet) for currents not listed, use the formula: 0.5 x 1000 maximum length = current x resistance where current is expressed in amps and resistance is expressed in ohms/km or ohms/1000 feet. If load regulation is critical, use remote voltage sensing . WARNING: While calculating load wire size, remember that the wire must be large enough not to overheat while carrying the current that would flow if the load were shorted. Table 3-3 lists the maximum current-carrying capacity (ampacity) for various sizes of stranded copper wire. If multiple loads are connected to one supply, each load should be connected to the supply's output terminals using separate pairs of connecting wires. This minimizes mutual coupling effects and takes full advantage of the supply's low output impedance. Each pair of connecting wires should be as short as possible and twisted or shielded to reduce noise pickup and radiation. If load considerations require the use of output distribution terminals that are located remotely from the supply, then the power supply output terminals should be connected to the remote distribution terminals by a pair of twisted or shielded wires. Each load should be separately connected to the remote distribution terminals. Remote voltage sensing is suggested under these circumstances. Sense either at the remote distribution terminals, or (if one load is more sensitive than the others) directly at the most critical load. 28 Operating Instructions Table 3-2. Maximum Wire Lengths To Limit Voltage Drops Wire Size Resistivity Maximum Length In Meters (Feet)To Limit Voltage Drop To 0.5V Or Less AWG Cross-section (mm2) W/kft W/km 5 A 10A 17 A 30A 50A 120A 22 16.15 (6.19) * * * * * 0,5 40.1 2.5 * * * * * 20 10.16 (9.8) * * * * * 0,75 26.7 3.7 1.8 * * * * 18 6.388 (15.6) (7.8) * * * * 1 20,0 5.0 2.5 * * * * 16 4.018 (24.8) (12.4) (7.3) * * * 1,5 13.7 7.3 3.64 * * * * 14 2.526 (40) (19.7) (11.6) (6.6) * * 2,5 8.21 12.2 6.1 3.5 * * * 12 1.589 (62.9) 13.46) (18.5) (10.49) * * 4 5.09 19.6 9.8 5.7 3.27 * * 10 .9994 (100) (50) (29.4) (16.68) (10.01) * 6 3.39 29.5 14,7 8.6 5.9 * * 8 0.6285 (160) (79.5) (46.7) (26.52) (15.91) * 10 1.95 51,2 25,6 15 8.55 5.13 * 6 0.3953 (252) (126.5) (74.4) (42.16) (25.3) * 16 1.24 80.6 40,3 23.7 13.44 8.06 * 4 0.2486 (402) (201) (118) (67.04) (40.23) (16.76) 25 0.795 125.7 62.8 37 20.96 12.58 5.24 2 0.1564 (639) (319) (188) (106.5) (63.94) (26.64) 35 0.565 176.9 88.5 52 29.5 17.7 7.37 50 0.393 254.4 127 74.8 42.4 25.45 10.6 0 0.09832 (1017) (508) (299) (169.5) (101.7) (42.38) * Wire not rated for power supply maximum current rating. Table 3-3. Stranded Copper Wire Ampacity Wire Size Ampacity NOTES: 1. Ratings for AWG-sized wires are derived from MIL-W5088B. Ratings for metric-sized wires are derived from IEC Publication 335-1. 2. Ampacity of aluminum wire is approximately 84% of that listed for copper wire. 3. When two or more wires are bundled together, ampacity for each wire must be reduced to the following percentages: 2 conductors 94% 3 conductors 89% 4 conductors 83% 5 conductors 76% 4. Maximum temperatures: Ambient, 50°C; conductor, 105°C AWG Cross Section (mm2) 22 5.0 20 8.33 0.75 10 1 13.5 18 15.4 1.5 16 16 19.4 2.5 25 14 31.2 4 32 12 40 6 40 10 55 10 63 8 75 6 100 4 135 2 180 0 245 Operating Instructions 29 Either positive or negative voltages can be obtained from the supply by grounding one of the output terminals. It is best to avoid grounding the output at any point other than the power supply output terminals to avoid noise problems caused by common-mode current flowing through the load leads to ground. Always use two wires to connect the load to the supply regardless of where or how the system is grounded. Never ground the system at more than one point. The maximum potential (including output voltage) that either output terminal is from ground must not exceed that specified on the output label on the rear chassis. The PARD specifications in Table 1-1 apply at the power supply output terminals. However, noise spikes induced in the load leads at or near the load may affect the load although the spikes are inductively isolated from the power supply. To minimize voltage spikes at the load, connect a bypass capacitor as shown in Figure 3-2. With this setup, peak-to-peak noise at the load can actually be reduced to a level below the value specified at the power supply output terminals. 500 Figure 3-2. Connecting a Bypass Capacitor Overvoltage Protection (OVP) The overvoltage trip point is adjusted at the front panel. The approximate trip voltage range is from zero v...

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