Integrated Filters

Integrated filters for power electronics represent an improvement over electrical filters made from discrete components. These patented [1-2] filters may be smaller, lighter, and more cost effective to manufacture than filters made from discrete inductors and capacitors. Integrated filters incorporate the electric field from a capacitor, and the magnetic field from an inductor in a single volume.

Integrated Filter Schematic
Figure 1 – Schematic view of the electric field in a capacitor, a magnetic field in an inductor, and both fields in the integrated device.

Integrated dv/dt Filters for Motor Protection

Integrated electrical filters work well as dv/dt filters for motor protection. Some motor and drive systems need filters to bring the system into compliance with the NEMA MG 1 Part 31 standard.

These filters are incorporated into the copper bus bars of wide bandgap Silicon Carbide motor drive systems [3]. In this application, the integrated filter is smaller and lighter than an equivalent filter made from discrete components. Figure 2 shows the film and foil wrapped around the bus bar. This device exhibits capacitance in the dielectric between the foil layers and inductance in the metal foil material encircling the current in the bus bar.

Figure 2 – Cross-section view of an integrated dv/dt filter incorporated onto a copper bus bar.

Then, by making the proper electrical connections, the integrated dv/dt filter can function as a low pass electric filter at the output of the motor drive. The filter lowers the dv/dt and limits the voltage overshoot. This protects the motor in a compact and efficient manner.

Integrated Filter Connections
Figure 3 – Experimental integrated filter incorporated into a motor drive bus bar showing the different terminals.

This filter has been experimentally tested on a 480 Volt, 30 HP motor and drive system. The filter mitigates the dv/dt, damps the high frequency ringing, and brings the system into compliance with the NEMA MG 1 standard.

Do you want to learn more or do you have questions about integrated dv/dt filters for motor protection or any other application? Get in touch!


[1] D. Ludois and A. Schroedermeier, “Integrated Capacitor and Inductor with Low Parasitic Inductance,” US9934903, 23-Apr-2018. (Link)

[2] D. Ludois and A. Schroedermeier, “Bus Bar with Integrated Voltage Rise Time Filter,” US15658989, 31-Jan-2019. (Link)

[3] A. Schroedermeier and D. Ludois, “Integrated Inductors, Capacitors, and Damping in Bus Bars for dv/dt Filter Applications,” 2018 IEEE Applied Power Electronics Conference and Exposition (APEC), 2018. (IEEEXplore Link)