How to avoid loops when the inverter is grounded at both ends

In applications where inverter cable shielding is double-grounded, avoiding harmful ground loops is crucial. Double-grounding provides a good return path for high-frequency common-mode noise, but if a potential difference exists between the two grounding points, a low-frequency ground loop current can form, potentially causing interference. Methods to avoid loops include: ensuring the inverter housing and motor housing (or remote equipment housing) are connected to the same grounding system via a low-impedance path, i.e., achieving effective equipotential bonding. Use grounding conductors with sufficiently large cross-sectional areas or utilize natural conductors such as mounting rails or metal cable trays to strengthen the equipotential bonding. Insert a common-mode choke in series in the shielding layer to increase loop impedance, suppress low-frequency loop currents, and maintain high-frequency grounding effectiveness.

For signal cables, use balanced transmission or differential interfaces. If equipotential bonding cannot be guaranteed, consider grounding one end of the shielding layer through a capacitor, creating a high-frequency ground and a low-frequency open circuit, but this may affect the shielding effectiveness for extremely low-frequency or DC signals. Loop risk can be assessed by measuring the ground potential difference across the shielding layer and the current flowing through it. Planning a unified grounding network in the early stages of system design is fundamental to avoiding double-ended grounding loops. Etymotic provides components and common-mode suppression devices for shielding grounding to help manage grounding loop issues.