eli5 why motors need drivers and cannot be powered directly or with potentiometer
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You can power a motor directly from a AC or DC source, it is done all the time. A desk fan you power from a out less it is unlikely to have a driver. A battery power fan can just have the motor connected to the battery via a switch to turn it on and off.
You can regulate the speed of a DC motor speed with a potentiometer, It is just a very inefficient way to do it. Triac designs like power tools uses are a lot more efficient.
All motors that result in continuous rotation are really AC motors. A motor with DC input has brushes and a commutator that physically changes how the coils are connected to the input. So mechanical AC generation. A drawback of this is the brushes can wear out
A brushless DC motor is really an AC motor with a driver that has DC input. The output to the motor is AC so the commutator and brushes are no longer required. The advantage is no brushes that wear out, and the torque and speed are also higher for a motor of the same size
If you want to control the speed of an AC motor you need a driver that changes the frequency. Today they work just like the controller of a brushless DC motor, the difference is just you need a rectifier at the input to create the DC the electronics used to produce the AC that you can change the frequency of.
So if the motor needs a driver or not depends on how you intend to use it and what type if motor and power input you have.
Many motors do not need specialized drivers. It depends a ton on the motor’s design and how it’s being powered.
The most basic motor, the brushed DC motor, cheats and uses the commutator as a “driver”. You can hook this up to a potentiometer, but you will lose a decent fraction of your energy into the potentiometer this way. There are AC motors that work similarly.
However if you need more power or efficiency, or you need better control of the speed and torque of the motor, a driver becomes incredibly helpful. This opens up your motor options quite a bit, and as electronics get cheaper these better systems are becoming more and more popular.
There are may different types of electric motor. some types can run straight off of DC current, others can run straight off of AC current, and some as you say require a driver.
The reality is ALL electric motors require a changing electric current to provide a changing magnetic field. Different motors accomplish this changing current in different ways. Motors that run directly from DC use a “commutator” — essentially a rotary switch built into the motor — to change the current. Motors that run off of AC current can use the sine wave of the input electricity to vary the current.
Using a motor driver (on the right type of motor) can improve efficiency and flexibility in output speed and power over other types of motors.
They don’t need a driver it’s simply for speed control unless you have a brushless DC motor then you need it
the hard part in making an electric motor is getting a rotating magnetic field if you don’t have this your motor will simply ocilate
the most common motor is the 3 phase induction motor it uses the grid’s 3phase power to achieve rotation brushless dc motors are 3 phase motors controled by turning dc power on and off very fast this is called pulse width modulation if you want to run a motor at variable speed from a battery this is normally what you use
brushed dc and universal motors use a commutator to achieve the rotating magnetic field no need for a driver single phase motors normally use a capacitor to shift the phase angle of the current to get rotation if you see a motor with a bulge in the side that’s what it is
You can power a.motor with a potentiometer if you leave one leg unconnected. Then it becomes a Rheostat or variable resistor. A potentiometer provides variable voltage by moving a wiper up and down a voltage divider. You want to vary resistance. Easily done. H Brodge drivers are more efficient because they used switched pulse signals that are always in full conduction or open circuit
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