In radio-controlled models, you can see that three capacitors are connected to the electric motor.One capacitor is parallel to the power supply, and the other two are from the power supply to the housing.The capacitance of the capacitors is mainly 0.1UF.Why do they do this?
This is done in order to get rid of the interference that the electric motor creates to the power source and the radio receiver.If the radio-controlled model uses interference-sensitive electronics, capacitors for the motor will be required. Capacitors eliminate or reduce power supply interference and high frequency interference.
You can see that if the capacitors are not connected to the motor housing, there will be interference on the housing during engine operation, they are visible as vertical stripes on the oscilloscope
Now I connect the capacitor to the housing and the interference has disappeared
Turn on the radio receiver next to the running electric motor.The receiver is tuned to frequencies of approximately 1700 kHz.You will hear a loud sound, this is interference that the electric motor emits.Now connect the capacitor in parallel to the power supply and the noise in the radio will become quieter.
