Rockwell Automation 8720MC 8720MC Regenerative Power Supply User Manual - Manual (Page 46)

4-8 Wiring
• 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]