Mobile Newsletter banner close. Mobile Newsletter chat close. Mobile Newsletter chat dots. Mobile Newsletter chat avatar. Mobile Newsletter chat subscribe. Solid State Electronics. The brushes eventually wear out. Having the electromagnet in the center of the motor makes it harder to cool. The use of brushes puts a limit on how many poles the armature can have.
The poles on the stator of a two-phase BLDC motor used to power a computer cooling fan. The brushes, as the rotor spins, make contact with the stator, flipping the magnetic field and allowing the rotor to spin a full degrees. A brushless DC motor is essentially flipped inside out, eliminating the need for brushes to flip the electromagnetic field.
In brushless DC motors, the permanent magnets are on the rotor, and the electromagnets are on the stator. A computer then charges the electromagnets in the stator to rotate the rotor a full degrees. Brushes eventually wear out, sometimes causing dangerous sparking, limiting the lifespan of a brushed motor. To demonstrate this idea, we present a comparison of two similar BLDC motors with different price ranges.
To compare the motors' performance, we used the RCbenchmark Series test stand. It is capable of measuring thrust, torque, voltage, current, RPM and efficiency. The data acquisition is done using the RCbenchmark software. The two motors tested are Ts of Kv and Kv respectively.
Both motors spin the same 7-inch propeller with a pitch of 4. The first graph in figure 7 displays the efficiency of both motors compared to the throttle. The second graph shows the efficiency at specific speeds. Clearly, the smaller Kv motor requires more throttle to run efficiently. The efficiency range is also better on the Kv motor, meaning the motor keeps a high efficiency at both low and top speed.
On the other hand, the smaller motor can operate at low speed and would probably be more efficient with a smaller propeller. A drone used for transport would use a smaller motor to be able to stay idle and stable at low speed, while for a racing drone, a bigger motor that would struggle to hover at lower speed would work just fine.
To get a full comparison, we would need to know the purpose of the drone and the RPM it will operate at. It is possible that the Kv motor is more efficient with a different propeller suited for a different function. Only through testing can we find out. The most important characteristic is motor Kv, which describes the rotation speed you get for the power input to the motor.
A motor with Kv will spin at rotations per minute for every volt sent to the motor. Size is closely related to the Kv. A wide and large motor will often have higher torque but lower Kv and use a bigger propeller, while a thin but longer motor will have high Kv, low torque and would be best suited for a small propeller. This makes sense when you consider that a larger motor operates at lower RPM while a small motor operates at relatively high RPM. The maximum power of a motor is also something to take into consideration.
Exceeding the motor's power restriction would result in the motor heating up and thus drastically lowering its efficiency or even damaging it. The brand can also change a motor's performance. For the same Kv value, a motor from one brand may perform better than others.
As a general rule, it is wise to use the smallest lightest motor possible without being in danger of overpowering and overheating it. The reason for this is to reduce the excess weight of a motor that is larger than needed. We have compiled a list of large motor manufacturers with products suitable for heavy-lift and manned drone operations. The brushless DC motor is a genius invention that has been a game changer in the world of electric propulsion.
Simple and streamlined in design, they allow vehicles like RC cars and drones to operate at high efficiency with maximum control. We also covered electromagnetism and how an ESC controls the speed of the motor. Difference between brushed motor and brushless motor. What are the disadvantages of brushless DC motors? And how can they be overcome? Contact us. How do brushless DC motors work? This page goes into detail about how brushless DC motors work.
Brushless DC motors offer long life and ease of maintenance. Brushed DC motors These motors work by means of the mechanical linkage between their commutator and brushes.
The brushes and commutator are in continual contact as the motor rotates. This causes wear of the motors by long-term use that can ultimately result in motor failure. For this reason, brushed DC motors have a shorter life than brushless DC motors, and require regular maintenance.
Another disadvantage is the electrical and acoustic noise caused by the continual contact between the brushes and commutator as the motor rotates. Brushless DC motors Instead of brushes and a commutator, these motors use electronic means a drive circuit to rotate the motor. How brushless DC motors work: Why is a drive circuit required? Outer-rotor motors These motors have the coils on the inside and the magnets on the outside, so that it is the outer circumference of the motor that rotates.
Although this configuration means that the moment of inertia of the rotor is high, it helps maintain steady rotation. Inner-rotor motors These motors have their magnets on the inside as the rotor, and the coils on the outside as the stator.
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