B&K Precision 1730A - Manual - Manual (Page 17)

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The working characteristic of the Model 1710A and 1730A Power
Supplies is called a constant voltage/constant current automatic crossover
type. This permits continuous transition from constant current to constant
voltage modes in response to the load change. The intersection of constant
voltage and constant current modes is called the crossover point. Fig. 7
shows the relationship between this crossover point and the load.
For example, if the load is such that the power supply is operating in the
constant voltage mode, a regulated output voltage is provided. The output
voltage remains constant as the load increases, up until the point where the
preset current limit is reached. At that point, the output current becomes
constant and the output voltage drops in proportion to further increases in
load. The crossover point is indicated by the front panel LED indicators.
The crossover point is reached when the CV indicator goes off and the CC
indicator comes on.
Similarly, crossover from the constant current to the constant voltage
mode automatically occurs from a decrease in load. A good example of this
would be seen when charging a 12-volt battery. Initially, the open circuit
voltage of the power supply may be preset for 13.8 volts. A low battery will
place a heavy load on the supply and it will operate in the constant current
mode, which may be adjusted for a 1 amp charging rate. As the battery
becomes charged, and its voltage approaches 13.8 volts, its load decreases
to the point where it no longer demands the full 1 amp charging rate. This is
the crossover point where the power supply goes into the constant voltage
mode.
CONNECTING TWO POWER SUPPLIES IN SERIES
Two Model 1710A or 1730A power supplies may be connected in series to
provide a variable 0-60 volt output. In this configuration, two 1710As
Figure 7. Constant Voltage/Constant Current Characteristic.
provide up to 1 amp; two 1730As provide up to 3 amps. See
Fig. 8 for the connection scheme.
When connected in series, the VOLTAGE controls of each
power supply exercise control over a 0-30 volt range. Add the
two V meter readings together to determine the total output
voltage, or an external voltmeter may be connected across the
load.
Load current may be monitored from either supply; the
readings will be identical since they are connected in series.
Also, since the supplies are connected in series, it is only
necessary to set the current limit on one of the supplies; the
other may be set for maximum.