The failure modes must all be considered throughout the traction inverter's design and implementation to ensure safe and efficient operation. Some mechanical or electronics failures that can impact the motor's performance related to the inverter system are shown in Table 2-2. Causes such as a motor short or open due to mechanical failure will not be discussed in this application note. Those failures that occur from the vantage point of the power electronics' will be discussed in more detail and the prevention mechanisms outlined in this section.

The voltage applied to the three windings of the motor, as previously discussed, determine the speed and torque of the motor. Disturbances can occur due to a variety of events. The power switching devices in the inverter, referred to as the IGBTs from this point on, may become shorted or open due to a mechanical failure, over-heating, etc. The gate driver itself could be a source for failure if it is damaged due to over-temperature or mechanical reasons, has a latched output, receives an incorrect signal from the MCU, or has experienced isolation barrier failure. To cover a variety of potential failures, the gate driver and auxiliary circuits are used to monitor the power switch for short circuit, proper gate voltage and other signals to protect the IGBTs and gate drivers. Additionally, circuitry is included to perform self-tests on critical functions in the case of a latent failure which occurs after a cycle of operation. Aside from the gate driver circuits, the MCU or PMIC should also have redundant monitoring circuits to prevent controller failure or supply failure.

The following sections introduce the UCC217xx-Q1 and the UCC5870-Q1 drivers, their integrated protection and diagnostic functions, and how they simplify the design of the traction inverter system. External circuits are also described, when necessary, to assist in performing self-tests and diagnostics.