High power motor applications can range anywhere from lower voltage systems that result in hundreds of watts, such as a 12-V automotive power seats, to multiple kilowatt systems, such as 60-V and 100-A power tools. Typically, these systems use shunt-based current sensing, and non-isolated gate drivers that control large power MOSFETs. While these applications can be powered from a battery or gridded AC power converted to DC, they all have the common goals to be robust and protected against high current and high voltage events that result from shoot-through, short-circuit, overcurrent, MOSFET reverse recovery, or PCB parasitic inductance behavior.
For example, power tools have high power ratings for industrial and household purposes, such as drilling, grinding, cutting, polishing, driving fasteners, and more. Requirements include:
When designing high power systems, these requirements produce tradeoffs and conflict with each other. In the case of power tools, high current, efficiency, and thermal performance can be an increased with a larger board size which conflicts with the need to be small and hand-held.
This makes high power design very important. Like in the case of Electromagnetic Interference (EMI), designing for high power applications is a process of making decisions and planning to mitigate problems that may or may not occur.
Surprisingly, poor high-power design does not always result in an electrical fire or smoke. The results are a spectrum. In the case of the electrical fire, the results may be instantaneous, and the first time the motor spins is also the last time the motor spins due to catastrophic board damage. This indicates that something is fundamentally faulty with the design, or some aspects of normal operation are amplified. As a result, some aspect of the design can be reduced or mitigated, controlling the source of damage and reducing its negative effects on the system to bring probability of damage to a negligible level.
In other cases, the motor will spin and damage might occur when commanded to deliver more current, or stop rotating. A change in operation stresses the system beyond what it is capable. In more difficult cases, the motor will spin at the same current or speed for a hundred hours but fail minutes before the test concludes. This could mean that a special use case might cause the design to fail, or regular operation might result in damage to the design over time until a permanent and observed failure occurs.
Understanding the differences in the spectrum allows the designer to understand what kind of change is needed to fix or prevent damage. Just like the spectrum of damage, the spectrum of changes could vary from replacing a component on the bill of materials to a complete redesign of the schematic and layout.