How to Measure Hairpins in an EV Motor Stator

Creepage distance describes the shortest distance along the insulating surface between the stripped pins. In EV motor stators, sufficient creepage distances are critical to prevent electrical breakdown and ensure long-term insulation reliability, especially under high voltage conditions.

In the eMotor Stator Inspection app, the function for calculating the creepage distances uses the insulation edges and pin axes as base elements. The result is a creepage curve. On this resulting element, you can perform the creepage distances check.

The paper height in the stator of an electric motor is crucial for ensuring proper insulation between the windings and the iron core, preventing short circuits and enhancing safety. It also aids in heat dissipation and provides mechanical stability to the windings, contributing to the motor's efficiency and longevity. Proper paper height helps maintain optimal magnetic properties and cost-effectiveness.

The airgap distance refers to the space between the hairpins in an electric motor. Maintaining a consistent airgap is critical for optimal magnetic flux, motor efficiency, and overall performance. Variations in the airgap can lead to increased losses, noise, or uneven torque generation. As part of quality control, the airgap distance is measured at multiple points along the pins to ensure it meets the nominal CAD specifications.

Hairpins in electric motors are typically insulated—either coated or lacquered—to prevent short circuits. To establish electrical connections, for example with end caps, weld points, or solder joints, the insulation must be removed at the ends. The length of the exposed copper along the pin’s axis is called the stripping height. This measurement must be precise, as deviations can lead to faulty electrical connections or damage the remaining insulation. As part of quality control, the stripping height is measured along the pin’s longitudinal axis, following the direction of the wire.

The eMotor Stator Inspection app provides the inspector with a clear quality assessment. The results are visualized in a color-coded way, which allows issues to be identified immediately. 

The pin height refers to the total length of a hairpin from its base to its tip. Accurate pin height is critical for ensuring proper fit within the stator slots and correct alignment with the end caps or other motor components. Deviations in pin height can cause assembly issues or affect the motor’s electrical performance. As part of quality control, each hairpin is measured along its longitudinal axis to verify that it conforms to the nominal CAD specifications.

The eMotor Stator Inspection app not only displays the measured values along with their deviations from the tolerances but also presents all measurements of a feature in a single overview. Any measurement points that are out of tolerance are highlighted in red. Since each pin is assigned an individual number, the user can quickly identify the faulty pins.