Rockwell Automation 8720MC 8720MC Regenerative Power Supply User Manual - Manual (Page 62)

4-24 Wiring
Capacity of built-in Capacitor
Built-in Resistor (Resistance Value/Wattage)
External Resistor (Minimum Resistance Value),
Connect to PR1 and PR2
External Circuit (Minimum Resistance Value),
Refer to figure 4.10
8720MC-RPS190 Unit
7600
µ
F
25000
µ
F
(10 ohm/400W)
165000
µ
F
(10 ohm)
495000 µ F
(1.5 ohm)
External resistor case
Most applications are successfully integrated using the internal
precharge resistor provided in the 8720MC-RPS Regenerative
Power Supply. For instances where there is a large amount of load
capacitance, caused by connecting several 8720MC drives to a
single 8720MC-RPS Regenerative Power Supply, an external
precharge resistor may be required. To determine the total
capacitance C[F] add the capacitance for the applicable RPS190
unit, as determined from row 1 of Table 4.5, to the sum of the drive
capacitance as determined by the drive specifications in Chapter 2
of the 8720MC-RPS User Manual, Publication 8720-UM-001-B-
US-P FEB 2001. In the case of the RPS190 if the total capacitance
is above 25,000
µ
f, but less than 165,000
µ
f an external precharge
resistor connected to PR1 and PR2 is required. Table 4.8 provides
the minimum resistance value for the external resistor od 10 ohms.
The wattage is determined by the equation presented above.
Connect the external precharge resistor to terminals PR1 and PR2
When Model 8720MC-RPS190 is adapted to Capacitors having
large capacity
8720MC-RPS190 unit charges to capacitors with a single phase,
full-wave rectification circuit through the built-in precharge/
discharge resistor. When the load capacitors have large
capacitance, it takes more time for charging, and the wattage of the
internal resistor becomes insufficient. When the load capacitance is
large, disable the built-in precharge/discharge resistor and connect
an external resistor or external circuit for precharging/discharging
(Note that minimum precharging/discharging cycle is 3 minutes).
Calculate a rated wattage of the external precharge/discharge
resistor to be connected to the outside in accordance with the
following formula depending on the total capacitance of all the
capacitors including the built-in capacitor.
Rated wattage [W] = 17000 x C[F]
But, serge resistivity of J[J] = 28000 x C[F] must be provided.
When an external precharge/discharge resistor is connected, change
the set value of the following parameters, if necessary.
• Precharge/Discharge Time (F.014)
• Wattage of Precharge/Discharge Resistor (F.015)
Table 4.8
Maximum Applicable Capacitance of Capacitor and Minimum Resistance Value