Rockwell Automation 8720MC 8720MC Regenerative Power Supply User Manual - Manual (Page 61)

4-23 Wiring
It is possible to select the 8720MC-RPS units depending on the
regenerative power when only regenerated power of the unit
integrating converter and inverter is used. In this case, however,
the following cautions must be observed. Figure 4.4 shows wiring
of the 8720MC-RPS027 or 8720MC-RPS065 unit used as a
converter for the power regeneration mode only.
• Rating of regenerative power of the 8720MC-RPS is less than
rated power both in the instantaneous rating and continuous
rating.
• When rectifier portion of inverter is composed of thyristor, CR
snubber circuit between anode and cathode of thyristor may
become overloaded. Therefore, treating time for regenerative
power must be within 5 seconds for 3 minutes. Because the
current "I
CR
" flowing through CR snubber circuit in the power
regeneration mode is represented by the following formula,
verify the specifications of CR snubber circuit.
• Do not fail to connect ACL unit of 3% impedance toward
inverter rating with the AC input line of inverter. Without ACL
unit, excessive circulating current will flow between the
8720MC-RPS units.
• Even during the power running, current will be supplied from
the 8720MC-RPS unit to DC bus proportionally to the impedance
ratio of both reactors at the 8720MC-RPS unit and inverter. This
current must not exceed the rating of the 8720MC-RPS unit.
• Set the parameter of the FWD Current Limit (U.001) to zero (0).
• Set the parameter of the Discharging Function Enable (F.017) to
zero (OFF).
• Set the DC bus voltage to start power regeneration to the
parameter of the DC Bus Voltage Reference (U.000).
• Open all the terminals PR1, PR2 and PR3 for connecting
precharge/discharge resistor. Because these terminals are open,
the unit does not perform precharge/discharge operations.
Precharge/discharge must be performed on inverter side.
• Do not fail to enter the READY signal of inverter to (PWR).
I
CR
[A] = (8 0.03 x R [
Ω
]) x C [
µ
F]