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Two N5751A supplies with paralleled outputs - no slave current

Question asked by dave.natrop on Dec 11, 2014
Latest reply on Dec 12, 2014 by dave.natrop
I have a configuration of two N5751A supplies with outputs wired in parallel.  The slave unit is not outputting any current.

The output voltage is set for 150 VDC, the OVP is at the power-on default (300 VDC), the UVL is at the power-on default (0 VDC),  and OCP is disabled.  The master delivers power, but there is no current output from the slave unit.  Per the instructions on pages 30 to 32 of the N5700 Users’ Guide, I have the outputs wired with 12 AWG  wire in parallel approximately 12 inches from the supply outputs.   Remote sensing has a sense point (+S, -S) connected to the master and then a parallel connection from the master to the slave remote sense inputs.  Using the rear panel J1 connector, there is a conductor from master J1-25 to slave J1-10.  There is a jumper wire from slave J1-8 to slave J1-12.
On the master, SW1-5 is UP and all other positions are in the factory-default DOWN.  On the slave, SW1-2 and SW1-5 are UP.  All other position on the slave SW1 are in the factor-default DOWN.

Using the Limit button, I set the current limit on the master to 1.0 A.  Likewise, on the slave I set the current limit to 1.2 A  When I enable the outputs of both the master and slave, I can increase the output voltage by turning the voltage adjustment **** on the master.  The display on the slave indicates that its voltage is the same as the master.  On the slave, neither the voltage adjust **** nor the current limit **** have any effect since the slave SW1-2 is in the UP position.  The voltage of the slave unit cannot be set independent of the master (higher or lower) because the voltage adjust **** has no effect.

With a load of 0.50 A connected to the paralleled outputs of the supplies, the master display indicates it is delivering current.  The slave display indicates a voltage, but the current value remains at exactly 0.  The constant voltage (CV) indicators on both supplies are on.  The constant current (CC) indicators on both the master and slave are off (not illuminated).  The PROT indicators on both supplies are off.  Changing the load demand either up or down has no apparent impact on the slave.  The slave delivers no current.  

In trying to debug, I temporarily decoupled the master and slave.  I verified that each supply, when configured as independent (stand-alone) power supplies, is capable of delivering their full rated current into my load.

Where am I going wrong?

Edited by: DNatrop on Dec 12, 2014 4:06 PM (typo)