BODY 1U2775 - Caterpillar

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 electromotive force that enables the flywheel to spin during start-up.
Generate an electromotive force during discharge that provides energy to the bus.
Illustration 6 g00729581
Field Coil CircuitThe 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 decreases.Inverters
There are two inverters in the system, the flywheel inverter and the utility inverter. The inverters are used for the reasons in the following list:
Develop the current that is necessary in order to rotate the flywheel.
Develop the voltage that is used during an outage.
Maintain the DC bus Voltage.Illustration 8 shows the way that the inverters are connected together. The system uses a 450 VDC split bus. The utility's neutral wire is the reference potential. This neutral is also connected to the neutral post on the armature of the flywheel.
Illustration 8 g00690715
System InvertersPower is provided by