Rockwell Automation 2364F Regenerative DC Bus Supply Unit (RGU) - Manual (Page 27)

Publication 2364F-5.01– October 2003
Overview 1-11
Precharge Operation for N-Code RGUs
The precharge circuit for the N-code RGU uses the main disconnect
(motor-operated circuit breaker, CB1) in place of a main contactor.
When MCP2 is closed and the start switch is turned on, the main
disconnect (CB1) remains open, the precharge contactor (M2) closes,
and current begins to flow through the precharge circuit (bypassing
the main 3-phase circuit). This precharge circuit (which has a
resistive load) charges up the capacitor bank. As the bank approaches
capacity, the main disconnect (CB1) closes, the precharge contactor
(M2) opens, and normal operation begins.
Figure 1.7
Precharge Circuit (N-Code RGU)
D C
B us
M otor-O perated
C ircuit B reaker
(C B 1)
Pow er S tructure
+
-
C apacitor
B ank
P recharge
C ontactor
(M 2 )
R
Precharge C ircuit
M otor C ircuit
Protector
(M C P 2)
Note: Older N-code RGUs may have a single-pha
precharge circuit (on L1 and L2).