RACE & ROLLER ASSEMBLY FORWARD & REVERSE PINION 5L5772 - Caterpillar

Power Electronics
The electronics perform the following functions:
Control the force that is required to unload the flywheel.
Rotate the flywheel.
Regulate the voltage that is on the DC bus.
Generate the voltage and the current that is used in the event of an outage.The four electronic assemblies are in the following list: static switch, field coil driver, utility inverter and flywheel inverter.Static Switch
Refer to illustration 1 in order to view the electronics for the static switch. The static switch assembly is composed of three discrete thyristor modules. One module is connected to each of the input phases. Each module has two devices. In the system, the devices are connected in parallel. However, the devices are connected in opposite directions. The functions of the static switch are in the following list:
Isolation of the input node during a discharge
Synchronization of the signals of the inverter node to the signals of the input node upon restoration of the input signals after an outage .
Initial charge of the DC bus
Illustration 1 g00655027
Static Switch AssemblyOne of the parallel sets of thyristors is turned on at a time. The thyristors only conduct current when the thyristors are forward biased. This is true for all three of the phases. Refer to illustration 2.
Illustration 2 g00690667
Sine Wave of the ThyristorUtility Inverter
Illustration 3 g00690668
Simplified Utility InverterThe utility inverter is used in order to charge the DC bus. The utility inverter contains a three-phase full wave rectifier and other electronics. The electronics rectify the AC voltage from the inverter node and the electronics invert the DC voltage back to AC voltage for the inverter node.Gate Signals
During start-up, the system monitors the AC voltage that is on each phase of the input node. The thyristors are turned on by the system at the proper phase angle in order to slowly increase the DC bus voltage. The gate signals operate at a frequency of 16 kHz. The gate signals have a duty cycle of 30 percent. The thyristors will begin to shift just before crossing zero. The thyristors are enabled for a period of time just before crossing zero. This period increases in order to increase the DC bus voltage. Refer to illustration 4. Once the DC bus charges to approximately 350 VDC, the gate signals will be enabled for the entire portion of the phase. Refer to illustration 5.During discharge or loss of utility, the utility inverter will invert the DC bus voltage to AC voltage that is 480 volts and 60 Hz. This power will be identical to the voltage that is provided by the utility.
Illustration 4 g00690670
Gate Signals of the Thyristor
Illustration 5 g00690674
Gate Signals of the Composite Static SwitchField Coil Drivers
The field coil that is on the top of the flywheel is connected between the positive rail and the neutral rail. The bottom field coil is connected between neutral and the negative rail. The field coils are used to generate magnetic fields in the flywheel which perform the following functions in the system:
Provide a lifting force on the rotor in order to prolong bearing life.
Generate an