Motor Designs

Motor Designs

What design capabilities Magnequench Technology Center have?

The applications team at the Magnequench Technology Center has experts with rich experience on design of various magnetic devices especially the permanent magnet brush and brushless motors, design and optimization of the magnetic fixture for magnetization of both isotropic and anisotropic bonded neo magnets.

Does Magnequench charges for the assistance in application or magnetic fixture design?

Magnequench Technology Center does not charge for the assistance in any application or magnetic fixture design if one of the following conditions is met.

  • The application has potential to use isotropic or anisotropic bonded neo and the present evaluations are pertaining to the use of such magnets.
  • Fixture design is for the magnetization of the isotropic or anisotropic bonded neo magnets.

For applications where other types of magnets are being considered of the magnetic fixture design for the magnetization of other magnet types may be considered on a case by case basis. Interested partie can contact either the nearest Magnequench office or the Magnequench Technology Center for further details.

What hardware or software does the Magnequench Technology Center have for the analysis, testing and design of magnetic application or magnetic fixture?

Some of the software and hardware is as mentioned below.

Software

  • SPEED- Analytical software for the design of permanent magnet brushed and brushless motors.
  • Vector Fields Opera – A 2D and 3D Finite element analysis software for the electromagnetic design and analysis
  • SOLIDWORKS – For 3D mechanical CAD
  • AutoCad- For 2D mechanical design

Hardware

  • Computer controlled dynamometer of various ratings
  • Cogging torque measurement setup
  • Test setup for skew angle and airgap flux density measurement
  • Capacitive discharge magnetizers including the pulse transformer and impulse magnetizer
  • Helmoltz coils
  • Powder testing using VSM
  • Magnet testing using Hysteresisgraph

Is it possible to replace ferrite with bonded neo in a motor without increasing the overall motor cost?

Yes, it is possible to replace ferrite with bonded neo in a motor without increasing the overall motor cost. Bonded neo magnets offer substantially better magnetic properties compared to ferrite. For certain applications, the size of the motor as well as the requirement of other raw material like copper and soft iron can be reduced substantially, resulting in lower motor cost.

How are isotropic bonded neo magnets useful in achieving reduced torque ripple?

By proper design of the magnetic fixture used for the magnetization of the isotropic bonded neo magnets, one can achieve the desired flux profiles such as radial, trapezoidal, sinusoidal or somewhere in between. Depending on the parameters like slot or pole combination, drive type to be used for brushless permanent magnet motor (sinusoidal or rectangular) etc., a proper profile for the magnetization of the magnets will be selected and the magnets will get magnetized. Hence by using bonded neo magnets, one can achieve desired airgap flux profile and reduced torque ripple without shaping the magnets, or the soft iron parts just by shaping the magnetization profile of the magnets, which is a great advantage from the manufacturing point of view.

For skewed magnetization of the ring magnet how to define skew angle of magnetization?

Please refer to the page 18 of the Magnetizing guide.
http://www.mqitechnology.com/downloads/articles/MagnetizingGuide.pdf

After receiving magnets from a magnet manufacturer, what are some ways to verify the consistency of the magnets?

There are various ways preferred by various users of the magnets. Some of the most common methods are as below:

  • Use a hall probe to measure the flux scan at the surface of the magnet using the hall probe
  • Use a hall probe to measure the airgap flux density for a closed magnetic circuit in which the armature/slotted part of soft magnetic material is replaced with the closed cylinder of the soft magnetic material
  • Assemble the magnet in the motor and measure the back emf
  • Use a gauss meter measure coil flux-linkage by fabricating a system in which a relative motion between the coil and magnet is generated.

What data does the Magnequench Technology Center need in order to begin assisting the analysis of a current design?

For Permanent Magnet Brushed (PMDC) Motor

  • Motor sample or the 2-D and 3-D drawing of the motor in AutoCad/SolidWorks compatible format.
  • Motor Performance characteristics or the Performance requirements like,
    • Starting torque, stall torque, starting current, stall current, rated speed, rated current, rated load torque/rated power, efficiency at the rated load torque/rated power, maximum allowable peak to peak cogging torque, no-load speed, no-load losses
  • Material Characteristics
    • Soft magnetic material B Vs. H and Loss characteristics
    • Brush characteristics
    • Type of Magnet and magnet property including the second quadrant characteristics of the magnet
  • Design Constraints if any,
    • Like maximum allowable diameter and length, winding type, no. of slots, minimum efficiency, maximum allowable peak to peak cogging torque etc.
  • Winding Arrangement
    • Turns/coil, Wire size, no. of coils or slot, slot pitch, winding front and back pitch

For Permanent Magnet Brushless (PMBLDC/PMAC) Motor

  • Motor sample with appropriate controller or the 2-D and 3-D drawing of the motor in a format which can be open in AutoCad/SolidWorks
  • Motor Performance characteristics or the Performance requirements like,
    • Starting torque, stall torque, starting current, stall current, rated speed, rated current, rated load torque/rated power, efficiency at the rated load torque/rated power, maximum allowable peak to peak cogging torque, no-load speed, no-load losses
  • Material Characteristics
    • Soft magnetic material B Vs. H and Loss characteristics
    • Brush characteristics
    • Type of Magnet and magnet property including the second quadrant characteristics of the magnet
  • Design Constraints if any,
    • e.g. Maximum allowable diameter and length, winding type, no. of slots, minimum efficiency, maximum allowable peak to peak cogging torque etc.
  • Winding Arrangement
    • Turns/coil, Wire size, no. of coils/slot, slot pitch, winding arrangement
  • Drive Details
    • Type of drive (Rectangular/ Sinusoidal)
    • Type of control (PWM/Hysteresis/Phase angle control)
    • Maximum allowable continuous current for the switches used in the drive

What are the commonly used adhesive materials to glue the isotropic bonded magnet with the back iron of the motor?

There are two alternatives 3M Scotch-Weld 2214 Hi-Temp and Loctite 332.

In a production type environment, one can consider to use the 3M Scotch-Weld 2214 Hi-Temp (original formula) when adhering a MQ1 type magnet to a steel surface. This adhesive can hold up to severe shock conditions, providing great shear strength, but it requires an oven cure cycle.

Please consider the following while deciding the material for the glue,

  1. 3M Scotch-Weld 2214 Hi-Temp. (Original formula) requires oven cure cycle. Please note that the 3M Scotch-Weld 2214 is not a two part adhesive.
  2. The 3M Scotch-Weld 2214 also requires an oven cure cycle. The demagnetization of the magnet due to an oven curve process will be highly related to the load line that the magnet is in while being exposed to the high temperature cure cycle.
  3. Loctite 332 is a two part adhesive that targets the permanent magnet market. It requires an activator but cures at room temperature.
  4. Two part adhesives might be a problem. They can do a good job when handled well, but introducing another variable can become an issue (too much activator can cause long term problems that cannot be detected immediately after assembly even with load testing).
  5. Surface preparation is typically a big factor. Thus, do ensure your frame surfaces are clean and void of oils, and slightly rougher surfaces (sandblasted vs. polished) typically provide much better adhesion. Coated magnet surfaces typically degrade adhesion performance, while a very smooth coated surface is the least desirable situation.
  6. When gluing a ring magnet to a hub, the application of the adhesive must be made to both the magnet surface and the hub surface as application to one surface does not provide proper wetting of the adhesive to the other surface when the two parts are joined. If not, one might not get the expected performance. Also a consistent glue gap around the full circumference of hub/shaft is important. One can either consider wounding up with the use of piano wire as spacers between the ring magnet ID and the hub or use fixtures to keep the ring concentric with the hub.

If your process cannot tolerate an oven curve process, then the Loctite 332 might be a good starting point (assuming its published properties meet the needs).

Please visit the respective 3M and Loctite website if you wish to find out more about the properties of the recommended adhesives.