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Why measure magnetic fields in electric motors?

Magnetic fields are the heart of every electric motor. Their exact shape determines efficiency, torque, noise behaviour and much more. That is why precise magnetic field measurement is a central part of modern test systems — especially in series testing and in the development of electric machines.

Our test systems enable high-resolution analysis of the magnetic fields in permanent-magnet and externally excited rotors — contactless, automated and in real time. That brings several advantages at once:

The advantages at a glance

  1. Defects found early, without destroying parts

    Deviations in the field point to production faults such as incorrectly inserted permanent magnets, material faults such as demagnetised components, and assembly faults such as misaligned rotors.

  2. Consistent performance across the batch

    Measured parts can be matched on purpose: a strong rotor paired with a slightly weaker counterpart, and the other way round. Less spread in performance, higher yield, despite the natural tolerances of the individual parts.

  3. Simulations validated against real parts

    In the development of new drive systems the magnetic field is often simulated. The real measurement serves to validate that simulation — essential for OEMs and tier-1 suppliers who want to build reliable, efficient drives.

  4. Evidence for safety and EMC

    Strong or unexpected stray fields interfere with sensors and control units and carry risk in medical and automotive applications. Measurement is how electromagnetic compatibility gets demonstrated and improved.

  5. Faster maintenance

    Mechanical damage or demagnetisation can also impair the magnetic field in operation and reduce efficiency. With magnetic field analysis, maintenance is targeted rather than blanket, with shorter downtimes and lower costs.

Functional testing of electric motors

Electric motors work through the interplay of electric currents and magnetic fields. The quality and orientation of these magnetic fields affect:

  • the torque
  • the efficiency
  • and the smooth running of the motor

Measuring the magnetic fields therefore helps to ensure that the motor works correctly.

Defect detection and quality assurance

Deviations in the magnetic field often point to:

  • production defects (e.g. incorrectly inserted permanent magnets)
  • material defects (e.g. demagnetised components)
  • assembly defects (e.g. misaligned rotors)

A precise magnetic field measurement system can detect these defects early and non-destructively — ideal for end-of-line test benches such as those developed by Koob Testsystems.

Safety and EMC (electromagnetic compatibility)

Strong or unexpected magnetic fields can:

  • interfere with other components (e.g. sensors, control units)
  • pose safety risks (e.g. in medical technology or automotive applications)

Magnetic field measurement helps to demonstrate and improve electromagnetic compatibility.

Validating simulation and development data

When new drive systems are developed, the magnetic field is often simulated. Real measurement serves to validate the simulation — essential for OEMs and tier-1 suppliers who want to build reliable, efficient drives.

Optimising motor performance and matching in series production

The magnetic flux density in the rotor has a major influence on the efficiency and performance of an electric motor. Precise magnetic field measurement makes it possible to:

  • improve the design in a targeted way,
  • use material more efficiently,
  • optimise weight and size (e.g. in e-mobility).

In series production, magnetic field measurement can also be used for targeted matching of components: rotors with particularly good magnetic properties can deliberately be paired with slightly weaker counterparts — and vice versa. This achieves consistent performance across the entire production batch, despite the natural tolerances of the individual parts.

This ensures:

  • consistent quality for the customer
  • higher yield in production
  • less variation in performance

Targeted maintenance

Mechanical damage or demagnetisation can also impair the magnetic field in operation and reduce efficiency. With magnetic field analysis, maintenance is targeted rather than blanket, with shorter downtimes and lower costs.

How Koob Testsystems can help

Koob Testsystems builds custom test systems for electric machines. Integrating magnetic field measurement into test benches makes it possible to:

  • ensure the quality of customers’ products
  • compare results against development data
  • detect defects automatically
  • meet regulatory requirements (e.g. in the automotive sector)

This makes Koob a partner that adds real value to the manufacture and development of modern electric motors.

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