An electric motor does draw more current when under load.
As more mechanical load is applied, the motor slows, the back emf decreases, and more current is drawn.
Depending on the size electric motors can draw between 1 to 20 amps and larger electric motors will draw around 30 to 50 amps and sometimes more.
A fan motor for example usually draws only 1 amp to 2 amps.
Things that can damage an electric motor include lack of lubrication, overheating, overloading, too much voltage, over current, moisture, humidity, dirt and contaminants and even vibration.
A good way to tell if an electric motor is burned out is to check the ohms of the motors windings.
You can test for a short circuit by checking the resistance of the windings with an ohmmeter; a reading of 0 ohms (Ω) indicates a short.
So long as the shell exists, a motor can be repaired and reconditioned.
The key is to remember that eventually that motor will need a burnout and rewind before it is insulated again.
Then, with proper maintenance and smart reconditioning, there is no limit to how many times you can have that motor repaired.
Electric motors do weaken overtime and also lose some of their torque because the heat overtime weakens the magnets and also messes up the windings.
The most common cause of motor failure, and arguably the most difficult to overcome, is low resistance.
Low resistance is caused by the degradation of the insulation of the windings due to conditions such as overheating, corrosion, or physical damage.
Electric motors rarely fail and when an electric motor fails it's usually because it's been overloaded, overheated, the bearings wore out or if it's a brush type motor the brushes wear out.
Sometimes the windings can get too hot and then burn out which then causes the electric motor to fail.
Electric motors don't really wear out but instead the bearings in the electric motor are what mostly wear out.
However the electric motor windings can also break down due to the heat and if the electric motor is worth it you may have the electric motor rewound.
The difference between a brushed motor and a brushless motor is that the brushed motor contains brushes and a commutator while the brushless motor does not contain the brushes or commutator and works on induction.
A brushed DC motor uses a configuration of wound wire coils, the armature, acting as a two-pole electromagnet.
The current's directionality is reversed twice per cycle by the commutator, a mechanical rotary switch.
This facilitates flow of the current through the armature; thus, the electromagnet’s poles pull and push against the permanent magnets along the outside of the motor.
The commutator then reverses the polarity of the armature's electromagnet as its poles cross the permanent magnets' poles.
A brushless motor, by contrast, utilizes a permanent magnet as its external rotor. In addition, it uses three phases of driving coils and a specialized sensor that tracks rotor position.
As the sensor tracks the rotor position, it sends out reference signals to the controller.
The controller, in turn, activates the coils in a structured way – one phase after the other.
DC motors can be better in some cases than an AC motor.
However AC motors are cheaper, tend to last longer and also are more powerful than DC motors.
AC motors also have better torque due to the higher voltage current they use.
The disadvantage of a DC motor is they require DC or direct current to run on and need transformers to change the voltage from AC to DC or you have to run them off of a DC battery.
Also DC motors are usually more expensive and also require brushes and commutators which can wear out overtime which adds to the cost.
DC motors have a high initial cost.
Maintenance cost is high and increased operation due to the presence of brushes and commutator.
Due to sparking at brush DC motors cannot operate in explosive and hazardous conditions.
You cannot run an AC motor on DC power directly as the motor would not have the correct current to start up and run.
The AC motor requires AC power while the DC motor requires DC power.
Although if you have an inverter that is big enough then you could plug the AC motor into the DC to AC inverter and power the AC motor off the DC power that way.
DC motors are continuous and can run for a very long time before they get too hot or wear the brushes out.
The rotation of the DC motor is accomplished by the force which is developed on a current-carrying conductor in a magnetic field.
The current-carrying conductor is connected to the shaft which is able to rotate relative to the stationary body of the DC motor.
You can run a DC motor continuous as long as it has enough power to the motor and as long as it does not overheat and until the brushes wear out.
Although it's not recommended to run a DC motor longer than a few hours or so at a time but they can run longer.
A 12v DC motor can run continuously 24/7 until the brushes wear out as long as the motor is not overloaded or doesn't get too hot.
A brushless motor can run 24 hours continuously as long as it's continuously rated although if it has a thermal shut down switch then the motor will shut down if the motor gets too hot.
If it does it usually takes longer than 10 hours and then the motor shuts down and has to cool off before it can be turned back on.
An electric motor can run for 24 hours a day 7 days per week as long as it's a continuous duty electric motor.
If it's not a continuous duty electric motor then it may only run for 10 hours or 24 hours before it gets too hot and needs to shut down.
An electric motor can work for 24 hours if the electric motor is a continuous duty electric motor.
If the electric motor gets too hot then it will shut off before it actually overheats due to a thermally protected motor switch.
So the electric motor can stay on for as long as it stays cool enough before it shuts off.
Some electric motors are rated to run continuous and can run 24/7 without shutting off for a very long time.
And then some motors may need to shut off after a 10 to 14 hours to cool down.
For DC motors they will usually overheat if left running longer than 15 hours or so and the brushes will wear out for a brush type DC motor.
But as for an AC electric motor that is brushless it will run and run until it either gets too hot or until the bearings wear out.
The bearings in an AC electric motor will most often wear out eventually after several months or years of continuous running.
But the motor itself is basically just a magnet that uses the electricity to turn the rotor and as long as power is supplied the motor can run and run and run.