Resolver Engineering

Basic Mechanism of a Resolver

A resolver is a type of rotation angle sensor for controlling the drive motor that is the power source of EVs. By efficiently controlling the motor, power consumption can be suppressed. To control the motor according to various driving conditions of a vehicle, it is necessary to detect the magnetic pole position of the motor and accurately grasp its rotational speed. The resolver serves as a sensor for these tasks.

Fixing method of small-diameter resolver

Stator mounting method (fixed plate)

• Mount to the housing in a loose fitting.
• Do not fix by press fitting.
• Fix the stator by fastening it with the fixing plate using bolts and nuts.

Rotor mounting method

• Mount to the shaft either in a loose fitting or press fitting. If the rotor has been fit in a loose fitting, fix the rotor by fastening it with the fixing plate using bolts and nuts.
• Do not perform press fitting that will deform the rotor.

Fixing method of large-diameter resolver (Bigger than 40VRX)

Mounting method of stator and rotor

• Fix the stator in a loose fitting with the coaxiality of the rotor (Recommendation: 0.1mm or less). Mount the rotor either in a loose fitting or by press fitting.
• Fix the stator to the housing with bolts and nuts, etc. using fixing holes.
• If the rotor has been fit in a loose fitting, fix it by fastening the rotor with the fixing plate using bolts and nuts.
• Do not perform press fitting that will deform the rotor. Doing so may degrade the accuracy.

• Fix the rotor and the stator using the fixing plate with bolts and nuts.
• Use your hands or a press when mounting the rotor and stator so that the product does not tilt. Do not strike the product with a hammer, etc. Doing so may degrade the electrical characteristics.
• Be careful not to damage the winding while performing work. Damaging the winding may result in the wire breaking or an insulation failure.

*Not sold by NMB Technologies Corp.

Resolver: Analog converter that converts the rotor’s mechanical rotation angle into electric signals based on electromagnetic induction.

VR Resolver: Variable reluctance type resolver.

Primary winding: Input winding (input side).

Secondary winding: Output winding (output side).

Input voltage: Voltage applied to the primary winding.

Output voltage: Voltage induced in the secondary winding.

Number of multiple: Value that shows the number of electric signal cycles that will be output when the rotor makes one revolution.

Transformation ratio: Ratio of maximum output voltage to input voltage.
(Transformation ratio = maximum output voltage / input voltage)

Phase shift: Shift in time of output voltage to input voltage.

Angle accuracy: Maximum error when the mechanical angle is 360°.

Input frequency: Frequency of the input voltage applied to the primary winding.

Input impedance: Minimum impedance at the input side.

Output impedance: Maximum impedance at the output side.

R/D (Resolver to Digital) conversion IC: Converts resolver signals into digital absolute position angle signals.