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Resolvers

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VR resolvers (variable reluctance resolvers) are angular displacement sensors that detect motor rotation angles and provide analog output signals. Featuring a simple structure without rotor windings or brushes, they offer excellent durability in harsh environments subject to heat, vibration, and dust. This robustness directly contributes to extended equipment service life and stable operation.
MinebeaMitsumi’s VR resolvers achieve highly accurate angle detection through advanced manufacturing techniques, maintaining copper wire winding precision to within half the specified tolerance.
To further enhance durability, TIG (tungsten inert gas) welding is used for wire connections instead of conventional soldering. During this process, the molten metal forms a spherical bead that encapsulates the copper wire, creating a highly resilient joint that minimizes the risk of vibration-induced wire breakage. This uniform bead shape also streamlines visual inspection; any joint defects, such as a deformed or collapsed bead, are easily identified during manufacturing. Ultimately, this ensures the consistent quality and reliability you need for your end products.

Applications

  • Automotive

  • EVs

  • Electric Power Steering (EPS)

  • Speedometers

  • Hybrid Vehicles

  • Electric Power Steering (EPS)

  • Integrated Starter Generator (ISG)

  • Brake-by-Wire (BBW)

  • Steer-by-Wire (SBW)

  • Valve Control

Resolvers Parts List

Click the arrow icon in the table below to switch from ascending to descending order.

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Parts

Number of multiple

Stator outer diameter
[mm]

Rotor inner diameter
[mm]
10VRX 2X-4X 25 6
15VRX 2X-5X 37 12
21VRX 2X-8X 52 18
26VRX 2X-8X 66 30
40VRX 2X-6X 101 45
52VRX 2X-6X 132 52
63VRX 2X-8X 160 93

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Product Topics

    Industry

    FAQ

    What are the key differences between brushless and VR resolvers, and how do I choose between them?
    The key difference lies in the rotor structure: Conventional brushless resolvers use rotor windings and a rotary transformer, whereas Variable Reluctance (VR) resolvers have no rotor windings or electronics.
    Brushless Resolvers:
    Deliver high accuracy for general servo applications, but require a longer axial length and higher structural complexity due to the internal rotary transformer.
    VR Resolvers:
    Feature a rotor made solely of stacked magnetic steel laminations. Placing all windings on the stator enables a thinner, lighter profile and lower manufacturing costs, making VR resolvers the industry standard for space-constrained EV traction motors and high-rpm applications.
    Please feel free to contact us if you need help selecting the right option.
    What is the difference between resolvers and encoders?
    Resolvers operate via analog electromagnetic induction, whereas encoders generate digital signals using optical or magnetic sensing.
    While optical encoders offer higher precision for position detection, their glass disks and internal electronics are vulnerable to dust, vibration, and extreme temperatures. Resolvers share the rugged structural characteristics of transformers, providing dependable performance in harsh environments. Consequently, they are the preferred solution for angle sensing in industrial equipment and automotive drivetrains where long-term durability is essential.
    Why are VR resolvers preferred for EV traction motors over optical or magnetic encoders?
    VR resolvers are chosen because they provide angular positioning without failure under extreme thermal shocks (often exceeding 150°C–200°C), mechanical stress, and aggressive fluids.
    Traction motors generate intense heat and continuous mechanical vibration that degrade optical encoder glass disks and built-in semiconductor electronics over time. Constructed strictly from high-grade silicon steel laminations and heavy-duty copper magnet wire, VR resolvers contain no fragile components. This mechanical simplicity guarantees ISO 26262 functional safety compliance and a extended service life in harsh automotive environments.
    What factors affect resolver position accuracy, and how can installation errors be minimized?
    Resolver transformation accuracy is mainly affected by air gap variations between the rotor and stator, axial eccentricity during installation, and external stray magnetic fields.
    Because VR resolvers detect angle through variations in magnetic reluctance, component machining tolerances and shaft concentricity during motor assembly directly influence signal linearity. Furthermore, strong leakage flux from the motor windings and electromagnetic interference (EMI) on signal cables can introduce position errors. Maintaining high accuracy requires targeted EMI mitigation, including magnetic shielding and twisted-pair shielded cabling.
    How are resolver output signals (SIN/COS) processed?
    Analog SIN/COS amplitude-modulated signals from the resolver are processed by a Resolver-to-Digital Converter (RDC) and transformed into digital angle data.
    By calculating the ratio of the two signals (typically using an arctangent algorithm), the RDC automatically cancels out common-mode noise caused by excitation voltage fluctuations or temperature drifts. The resulting high-resolution digital position data is then transmitted to the motor control unit (MCU) or host system via serial or parallel interfaces for real-time torque and speed control.

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