Rockwell Automation SA3000 High Power Modules - Manual (Page 18)

2-6 High Power SA3000 AC Power Modules
2.2 Electrical Description
DC bus input power is applied to the Power Module through terminals 45 (–) and
47 (+), passes through the optional DC bus disconnect and in-line fuses, and is then
fed to the optional pre-charge circuitry. See figures 2.4 to 2.7.
When pre-charge circuitry is present and DC input power is applied, the internal DC
bus begins charging through the pre-charge resistors. Once the DC bus capacitors
are fully charged (per the programmable threshold value) and all pre-charge criteria
are met, the internal pre-charge contactor closes and bypasses the pre-charge
resistors. If the DC bus disconnect option is not used, the bus supply is responsible for
the charging operation. Refer to Appendix B for additional information on SA3000
internal DC bus control.
The DC bus voltage is filtered and stored by the electrolytic capacitors. Discharge
resistors are designed to discharge the capacitors down to 50 VDC within 5 minutes
after power is removed from the input terminals. However, if a DC bus fuse has blown,
it is possible for a charge to be stored on the DC bus capacitors without being
indicated on the DC bus voltmeter. Wait 10 minutes before working on the unit. Be
sure to measure the DC bus potential of each Power Module capacitor bank before
touching any internal circuitry. See figure 4.1 for test point locations.
When the DC bus operating voltage is reached, the connected Inverter Power
Modules may be operated. Note that if an SB3000 Power Module is used to supply the
DC bus, the SB3000 Power Module cannot support the loading of SA3000 Inverter
Power Modules when the soft-charge resistors in the SB3000 are limiting the bus
charging current.
The SA3000 inverter power circuitry uses the filtered DC bus voltage to provide the
variable-voltage, variable-frequency output to the motor (terminals U, V, W). The 972
Amp and 1457 Amp units have reactors for load sharing on their outputs. The IGBTs
are switched by the gate drivers on the IGBT phase module under the control of the
PMI rack. A LEM sensor is located on each output phase (U,V,W) of each SA3000
Inverter Power Module (A,B, or C) to provide output current feedback for overcurrent
protection.
!
ATTENTION: DC bus capacitors retain hazardous voltages after input
power has been disconnected. After disconnecting input power, wait ten
(10) minutes for the DC bus capacitors to discharge. Open the cabinet
doors and check the voltage across the DC bus bars, 347 A,B,C (+ bus)
and 345 A,B,C (- bus), with an external voltmeter to ensure the DC bus
capacitors are discharged before touching any internal components.
Failure to observe this precaution could result in severe bodily injury or
loss of life.
!
ATTENTION: When used with an SB3000 bus supply, the SA3000 Power
Module must be in standby or in regeneration whenever the SB3000
Power Module’ s pre-charge contactor opens. The SB3000 Power
Module’s soft-charge resistors may fail if this interlocking restriction is
not observed. Failure to observe this precaution could result in damage
to, or destruction of, the equipment.