TM 11-6625-2958-14&P
Figure 3-2.Normal Strapping Pattern
3-7CONSTANT VOLTAGE
3-8 To select a constant voltage output, proceed as follows:
a. Turn on power supply and adjust VOLTAGE controls for desired output voltage with output terminals open.
b. Short circuit output terminals and adjust CURRENT controls for maximum output current allowable (current limit), as determined by load con- ditions. If a load change causes the current limit to be exceeded, the power supply will automatically cross over to constant current output at the preset current limit and the output voltage will drop proportionately. In setting the current Iimit, allowance must be made for high peak currents which
can cause unwanted crossover. (Refer to Paragraph 3-60.)
3-9CONSTANT CURRENT
3-10 To select a constant current output, proceed as follows:
a. Short circuit output terminals and adjust CURRENT controls for desired output current.
b. Open output terminals and adjust VOLTAGE controls for maximum output voltage allowable (voltage limit ), as determined by load conditions. If a load change causes the voltage limit to be ex- ceeded, the power supply will automatically cross over to constant voltage output at the preset voltage limit and the output current will drop propor- tionately. In setting the voltage limit, allowance must be made for high peak voltages which can cause unwanted crossover. (Refer to Paragraph 3-60.)
3-11OVERVOLTAGE TRIP POINT ADJUSTMENT
3-12 The crowbar trip voltage can be adjusted by using the screwdriver control on the front panel. The trip voltage range is as follows:
6259B, 6260B | 6 2 6 1 B | 6268B, 6269B |
2 to 12Vdc | 2 to 23Vdc | 4 to 45Vdc |
When the crowbar trips, the output is shorted and the amber indicator on the front panel lights.
Clockwise rotation of the control produces higher trip voltages. The factory sets the control fully clockwise. The crowbar may be disabled completely if desired. (Refer to Paragraph 5-111.)
3-13 False crowbar tripping must be considered when adjusting the trip point. If the trip voltage is set too close to the operating output voltage of the supply, a transient in the output will falsely trip the crowbar. It is recommended that the crowbar be set higher than the output voltage by 5% of the output voltage plus 2 volts. However, If occasional crowbar tripping on unloading can be tolerated, the crowbar trip point can be set much closer to the operating out put voltage of the supply.
3-14CONNECTING LOAD
3-15 Each load should be connected to the power supply output terminals using separate pairs of connecting wires. This will minimize mutual coupling effects between loads and will retain full advantage of the low output impedance of the power supply. Each pair of connecting wires should be as short as possible and twisted or shielded to reduce noise pickup. (If a shielded pair is used, connect one end of the shield to ground at the power supply and leave the other end unconnected.)
3-16 If load considerations require that the output power distribution terminals be remotely located from the power supply, then the power suppIy output terminals should be connected to the remote distribution terminals via a pair of twisted or shielded wires and each load should be separately connected to the remote distribution terminals. For this case, remote sensing should be used. (Refer to Paragraph 3-4 1.)
3-17 Positive or negative voltages can be obtained from this supply by grounding either one of. the output terminals or one end of the load. Always use two leads to connect the load to the supply, regardless of where the setup is grounded. This will eliminate any possibility of output current return paths through the power source ground which would damage the line cord plug. This supply can also be operated up to 300Vdc above ground, if neither output terminal is grounded.
3-18 NO LOAD OPERATION
3-19 When the supply is operated without a load, down-programming speed is considerably slower than in normal loaded operation. This slower programming speed is evident when using any method of down-programming - either turning the VOLTAGE controls fully counterclockwise, activating the crowbar, or throwing the LINE circuit breaker to OFF. Under any of these conditions, the supply output will rapidly fall to approximately two volts,
