Noise suppression of brush motor for cars

Frequent Issues

Is it possible to add a capacitor for noise suppression in a high-temperature environment with minimum space?

Recently, electronization of car designs has been advancing. Since the number of units installed in cars has increased, the design space for each part has decreased. Furthermore, there are many cases where measures to suppress noise are required in the units, where noise suppression measures have never been taken before.
Company C, which designs and manufactures motors for cars, was also concerned about noise suppression measures in small design spaces.

- Example Case: Company C -
It is necessary to add a capacitor, but a printed circuit board cannot be used.

Company C was struggling to come up with a means to suppress noise with a capacitor. They searched for a capacitor from an available catalog; however, the only capacitor they found was a chip type that is mounted on a board by soldering.
However, a dedicated locking pin is required to fix the board to the motor for a car. In addition, a general glass epoxy board cannot be used in a 150°C environment.
This is not realistic, as the costs will greatly increase due to the orders for dedicated locking pins and using a board made of a material that can handle a high temperature environment.
Even if a capacitor for noise suppression were added to a board that could control the environment to a temperature lower than the periphery of the motor, it would not be effective because the board is mounted away from the motor, which is the noise source. If the components cannot be directly mounted to the motor unit, it is difficult to suppress the noise.
Leaded products are required for direct mounting of the components to a motor unit.

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"I would like to mount a capacitor by welding"
Can such a special request be realized?

Recently, manufacturers that sell leaded products are decreasing.
Furthermore, after confirming with an internal welding engineer, it became clear that it was difficult to perform the welding unless copper was used as the material of the lead wires, if the facilities owned by Company C were used. There are many cases where the lead wires of capacitors are made of low carbon steel, which makes it even more difficult to select a capacitor.
Company C approached Murata, which offers a variety of leaded products. Company C was able to find a solution for a difficult issue.

Points of Issue

  • POINT1
    There is no space to mount a board
  • POINT2
    To directly mount a capacitor to a motor terminal
  • POINT3
    Steel lead wires cannot be used in the internal welding process
The Solution

To examples of adding capacitors for noise suppression in a minimum space