TM 11-6625-2958-14&P
on the maximum voltage rating of the "master" sup- ply. The value of RX is this voltage divided by the voltage programming current of the slave supply (1/Kp where KP is the voltage programming coeffi- cient). The voltage contribution of the slave is determined by its voltage control setting.
3-53 Overvoltage protection is provided in Auto- Series operation by connecting the crowbars in parallel with correct polarity as in Auto-Parallel operation (see Paragraph 3-49). The OVERVOLTAGE ADJUST potentiometer in each supply should be adjusted so that it trips at a point slightly above the output voltage that the supply will contribute.
3-54 When the center tap of an Auto-Series combination is grounded, coordinated positive and negative voltages result. This technique is commonly referred to as “robber-banding” and an external reference source may be employed if desired. Any change of the internal or external reference source (e.9. drift, ripple) will cause an equal percentage change in the outputs of both the master and slave supplies. This feature can be of considerable use in analog computer and other applications, where the load requires a positive and a negative power supply and is less susceptible to an output voltage change occurring simultaneously in both supplies than to a change in either supply alone.
3-55AUTO-TRACKING OPERATION (Figure 3-12)
3-56 The Auto-Tracking configuration is used when several different voltages referred to a common bus must vary in proportion to the setting of a particular instrument (the control or master). A fraction of the master’s output voltage is fed to the comparison amplifier of the slave supply, thus controlling the slave's output. The master must have the largest output voltage of any power supply in the group. It must be the most positive supply in the example shown on Figure 3-12.
3-57 The output voltage of the slave (Es) is a percentage of the master's output voltage (EM), and is determined by the voltage divider consisting of RX and the voltage control of the slave supply, Rp, where ES = EM [Rp/(Rx+Rp)]. Remote sensing and programming can be used (each supply senses at its own load), though the strapping patterns given in Figure 3-12show only local sensing and program- ming. In order to maintain the temperature coefficient and stability specifications of the power sup- ply, the external resistors should be stable, low noise, low temperature coefficient (less than 30ppm per degree Centigrade) resistors.
3-58 The overvoltage protection circuit in each unit is operable end independently monitors the voltage across its own load. Notice that if the master supply crowbars, the output voltage of
Figure 3-12.Auto-Tracking, TwO and Three Units
each slave will also decrease. However, the reverse is not true. If one of the slave units crow- bars, the other supplies in *the ensemble will not be affected.
3-59SPECIAL OPERATING CONSIDERATIONS
3-60“PULSE LOADING
3-61 The power supply will automatically cross
