Page 9 - PCIM and APEC 2021 - Technical Coverage, eBook

APEC - MOTOR APEC - Motor

Figure 1: Expectation with SiC MOSFET compared with Si devices

SiC’s elevated electron mobility enables faster switching speeds to be supported. These faster
switching speeds mean that, in turn, the associated switching losses will be reduced. Its dielectric
breakdown field strength is almost an order of magnitude higher than Si. This allows a thinner
drift layer to be implemented, which translates into lower on-resistance figures. Also, as SiC has

triple the thermal conductivity of Si, and it is much more effective at dissipating heat energy.
Consequently, thermal stresses are much easier to mitigate.

Conventional high-voltage motor drives will have a three-phase inverter arrangement, with Si
IGBTs accompanied by integrated anti-parallel diodes. The three half-bridge phases drive the
corresponding phase coils of the inverter to deliver a sinusoidal current waveform that subsequently
runs the motor. The energy wasted in the inverter will come from two main sources — namely

conduction losses and switching losses. By replacing the Si-based with SiC-based switches, both
Silicon Carbide’s Role of these losses can successfully be combated.

Rather than using anti-parallel
in Next-Generation Si diodes, SiC Schottky

barrier
can
diodes
be
Industrial Motor Drives incorporated into the system.
While the Si-based diodes
have a reverse-recovery

By Corporate Marketing at onsemi current that contributes to
switching losses (as well as
The International Energy Agency (IEA) at onsemi estimates that motors are responsible for more generating electromagnetic
than 45% of the world’s total electricity. Thus, finding ways to maximize their operational efficiency interference, or EMI), the
is paramount. Higher-efficiency drives can be smaller and moved closer to the motor, which reduces SiC diodes have a negligible
challenges arising from long cables. This will have relevance from an overall cost and ongoing reliability reverse-recovery current. This
perspective. The advent of wide-bandgap (WBG) semiconductor technology is expected to play a enables switching losses to be

major role in enabling new motor efficiency and form-factor benchmarks to be achieved. reduced by as much as 30%.
Because the EMI these diodes
The use of WBG materials, such as silicon carbide (SiC), means that devices can be fabricated and generate is much lower, the
are able to outperform their silicon (Si) equivalents. Though there are various key opportunities for need for filtering will not be
this technology, industrial motor drives are receiving the greatest interest and attention. as great either (resulting in Figure 2: onsemi solutions

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