If you have ever disassembled a children's car and taken out small motors from it, you may have noticed that each of them has a small capacitor soldered to the power terminals.
If you unsolder it and check the operation of the motor, then practically nothing will change. So why is it needed?
Capacitors with a capacity of 0.1-0.01 μF are usually soldered parallel to the terminals of collector electric motors.
Let's check it out experimentally
Let's take the motor and unsolder the capacitor. Take a voltmeter and connect it parallel to the motor terminals. For power supply we will use two AA batteries connected in series, with a total voltage of 3 V.
When turning the motor on and off from the power supply, high voltage pulses up to 1000 V appear
This is normal, no one has yet canceled the EMF of self-induction. Moreover, such jumps were not observed with the capacitor.
I also call such impulses reverse current; they are usually destructive for any circuit where there is electronics. This is the first reason why this capacitor is installed.
Changes in work
Now let's connect each engine separately and listen to their operation by ear.
The changes are certainly not obvious, but the motor without a capacitor works with chatter and is no longer stable. This is the second reason for installing a capacitor: spark extinguishing, which increases the life of the brushes and the engine as a whole.
And finally, the third thing a capacitor is used for is noise immunity. If you turn on any radio while the motor is running without a capacitor, you will clearly hear the noise emitted by the motor commutator.
Bottom line: why does an electric motor need a capacitor?
During operation, a commutator motor constantly switches the armature windings. Using a capacitor in the motor power circuit solves the following problems:
- The first is spark extinction on the commutator brushes.
- The second is noise protection.
- Third - protection of the supply circuit from reverse current.
