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diagnose any possible gate degradation of the SiC MOSFET and thus predict its remaining lifetime based on some estab- lished models. One example of this is TI’s UCC5870-Q1, which measures the SiC MOSFET gate threshold voltage and reports back to the controller during every power-up. This measurement result can be tracked for the whole operation time of the motor drive.
As the voltage range of SiC MOSFETs increases, they will be able to replace series- connected IGBTs, reducing the solution size, weight, and cost. When will SiC MOSFETs with a several-kilovolt voltage range be available?
Wang: Multi-kilovolt SiC MOSFETs [all the way up to 15 kV] are available today and can be seen in various articles being issued by universities, consortia, and the Department of Energy. To enable and expedite the commercialization of high-voltage multi-kilovolt SiC MOSFETs, one key consider- ation is how to drive this high-working–voltage SiC with a >40-year galvanic isolation barrier lifetime. The high working voltage of capacitive isolation technology can help address the high-voltage–isolation requirement inside the chip with significantly higher TDDB than opto-based isolation and inductive isolation, and this translates to a longer lifetime and higher reliability at a higher operating voltage.
Besides TDDB, another consideration is the package develop- ment used for the isolated gate driver to achieve the required creepage and clearance distance.
Speer: For sure, the market is hungry to replace 3.3-kV– plus IGBTs with SiC, as all of the benefits we’ve discussed today are only more substantial as the voltage requirements increase. It may be worth reflecting that the first SiC power transistor at 1,200 V was released almost exactly 10 years ago today. The release of the first transistor followed the release of the first SiC Schottky diode at 650 V, 10 years prior. So we can expect to see higher-voltage SiC solutions being released in very short order to meet the needs you described: simplify- ing multi-level architectures and control schemes by going to a simple, two-level hard-switched design with improved performance and reliability to match.
What will be curious is at what voltage class the SiC market will choose to go from a unipolar device like a MOSFET to an alternative device design. What we see in the silicon world is that most suppliers offer an IGBT once the blocking voltage goes above 600 or 900 V. If SiC has 10× the breakdown field, will the same trend occur from MOSFETs to IGBTs at 6.5 kV? We shall see. Either way, SiC is here to stay and promises to
The use of SiC in motor control applications enables energy savings, size reduction, integration opportunities, and reliability.
completely upend power conversion from what’s been pos- sible with silicon.
Conclusion
Motor control technology, particularly the frequency- controlled drive, has evolved very rapidly in recent years as motor use has skyrocketed in various application contexts and as the potential to save massive amounts of energy has become clear. Since their introduction, frame-based power modules for motor control have been a game changer for various aspects of application fields that are particularly sen- sitive to cost, size, and performance optimization.
The industrial automation sector is certainly the most emblematic example. A servo drive is the motor activation element in many types of automated production equipment, such as robots and transport belts. The ohmic conduction losses and fully controllable switching transients of SiC MOSFETs offer a perfect match for their load profile.
The use of SiC devices in motor control and electrical power control applications in general is a real breakthrough, enabling energy savings, size reduction, integration oppor- tunities, and reliability. Among other options, in inverter cir- cuits, it is now possible to use the optimum switching fre- quency for the connected motor, which leads to important advantages in motor design.
Stefano Lovati
is a technical writer for Power Electronics News and EEWeb.
Maurizio Di Paolo Emilio
is editor-in-chief of Power Electronics News and EEWeb.
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Technology Analysis Motor Control Design with SiC Power Devices