Appendix D Application For Pm2812 And Pm2813 - Fluke PM2811 User Manual

Application for PM2812 and PM2813
APPENDIX D
APPLICATION FOR PM2812 AND PM2813
The following application support information is meant for the user who wants to
extend the maximum current of the PM2812 or PM2813 Power Supply by parallel
connection of channels.
PARALLEL CONNECTION OF OUTPUT CHANNELS
When you connect output channels in parallel to a load, be aware of the following:
The 'down programmer'
This is a circuit in the output channel that unloads the internal filter capacitors
when the output voltage is set to a lower value, to achieve a short response time.
The down programmer will have the same effect on (external) capacitive loads to
shorten the response time. The down programmer will sink a fixed current (about
10% of the rated current) as long as the voltage on the channel output is higher
than the programmed setting.
The down programmer will influence also the result of parallel connected
channels when the channels are set to different voltages. The channel set to the
lowest voltage will activate its down programmer, which will behave as a constant
current load. This current is not shown by the display or by readback. Then the
total current through the load is not equal to the total readback current of the
channels.
Example:
Vset = 12V
Iset = 5A
CH1
CC
Vset = 10V
Iset = 5A
CH2
CV
Figure D.1 Channels connected in parallel to a load. CH 1 in Constant Current
mode, CH 2 in Constant Voltage mode.
5A
10V
10V 8A
3A
10V
1.25
D - 1