Rockwell Automation 2364P Parallel DC Bus Supply Config. - Manual (Page 23)

Publication 2364P-5.01 December 1999
Theory of Operation 1-11
Precharge Operation
When the disconnects are closed and the start switch is turned
on, each RGU in the parallel configuration will begin its
precharge routine. This routine charges the capacitors on the
DC bus (the RGU capacitor bank and inverter capacitors) in a
controlled fashion.
Two contactors (M1 and M2) are used to perform the precharge
operation in the K, L, and M-code RGUs (the N-code RGU precharge
circuit is slightly different).
When the disconnect (MCP1 or CB1) is closed and the start switch is
turned on, the main contactor (M1) 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 contactor (M1)
closes, the precharge contactor (M2) opens, the NRU circuit breaker
closes, and normal operation begins.
Figure 1.18
Precharge Circuit
Circuit Breaker or
MCP
(CB1 or MCP1)
Main
Contactor
(M1)
Precharge Circuit
Precharge
Contactor
(M2)
R
Note: The precharge circuitry is slightly
different in the N-code RGU. See the product
schematics for further details.