SWITCH AS-TOGGLE 8C9812 - Caterpillar

Power Electronics
The electronics perform the following functions:
Control the force that is required to unload the flywheel.
Rotate the flywheel.
Regulate the DC bus voltage.
Generate the voltage and the current that is used in the event of an outage.There are four electronic assemblies: static switch, utility inverter, field coil drivers and flywheel inverter.Static Switch
Illustration 1 g03404378
Static switch assemblyThe 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 2 g01007660
Sine wave of the thyristor for phase AOne 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.Gate Signals (Static Switch)
Illustration 3 g03404380
Gate signals of the thyristor
Illustration 4 g01007665
Gate signals of the composite static switchDuring 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. Refer to illustration 3. 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 4.Utility Inverter
Illustration 5 g03404381
Simplified utility inverterThe utility inverter is used in order to charge the DC bus. The utility inverter contains a three-phase full wave insulated gate bipolar transistor (IGBT). The insulated gate bipolar transistors (IGBTs) rectify the AC voltage from the filter node. The insulated gate bipolar transistors (IGBTs) invert the DC voltage back to AC voltage during discharge.Field Coil Drivers
Illustration 6 g00802180
Field coil circuit (1) Top field coil (2) Bottom field coilThe insulated gate bipolar transistors (IGBTs) for the field coil are connected to the 400 VDC bus. 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 electromotive force that enables the flywheel to spin during start-up.
Generate an electromotive force during discharge that provides energy to the bus.The amount of current through the top field coil and the bottom field coil is controlled by the two Insulated Gate Bipolar Transistors (IGBTs) that are connected across the field coils.
Illustration 7 g00690678
Gate signals of the field coilOne driver is always on. When both of the drivers are on, the current that is in the coil is increased.The unloading force and the speed of the flywheel determine the current that is applied to the field coils. As the speed of the flywheel increases, the field current that is needed