Power Tools: Understanding DC & Brushless Motors

In summary, the use of electric motors in power tools has evolved from brushed DC motors to brushless technology due to higher efficiency, torque, and lower maintenance requirements. AC motors, specifically induction motors, are not commonly used in power tools due to their slower speed and lower efficiency compared to brushed DC and brushless motors. To obtain information for calculations, contacting manufacturers or researching online are suggested methods.
  • #1
homer5677
6
0
Hey guys,

Currently doing a task on electric motors and their uses in things. I have chosen to do power tools (specifically cordless drills) as I am aware that many have employed brushed DC motors but now use brushless technology.

Firstly, I don't know if any of you guys have done something similar to this or not as I am having trouble finding information that I need to perform calculations (ie: effciency, synchronus speed, power, torque, work, moment of inertia...etc)
I HAVE TRIED EMAILING COMPANIES TO NO AVAIL.
If you guys have any suggestions on ways of obtaining this information it would be great.

Secondly, I need to compare these two motor types to another electric motor type being one that is AC. I don't really understand how an AC motor works and anything that I have read has not made any sense to me (including 3 phase design??).
I am planning to explain why and AC motor (such as induction??) is not used in power tools and the reasons why, comparing it to what is actually used. Any insight into why this is the case would be also great!

Equations:
So far I have these but with key missing parts.

Efficiency:
μ = Poutput/Pinput (W)

Total Speed: (I know this is already listed as max rpm on websites, however i want to be able to prove this)

Srpm = 120 * F (supply frequency-cycles/sec) / P (number of winding poles)

Torque:
τ = F * D (is this the right equation for this)

And any other that you guys think would be necessary for this investigation.Here are some links to some of the tools i am talking about.

Any input would be much appreciated.:smile:
Thanks
 
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  • #2
Yes, the equation for torque is τ = F * D. The AC motor type that you are talking about is an induction motor. This type of motor is not typically used in power tools because it is slower and inefficient compared to brushed DC and brushless motors. Brushed DC and brushless motors are more efficient and have higher torque values than induction motors. Additionally, brushless motors are quieter and require less maintenance than brushed motors do. To obtain the information needed for your calculations, you may need to contact the manufacturers of the power tools directly. They should be able to provide you with the necessary data. Alternatively, you can search online for technical specifications about the motors used in the power tools.
 

1. What is the difference between DC and brushless motors?

DC motors use direct current (DC) to power the motor and create movement, while brushless motors use an electronic commutation system to switch the direction of the magnetic field, resulting in smoother and more efficient rotation.

2. How do DC and brushless motors work?

DC motors use a split-ring commutator to switch the direction of the current flow in the coils, which creates a rotating magnetic field that interacts with the permanent magnets to produce motion. Brushless motors use electronic sensors and a circuit board to switch the direction of the magnetic field, eliminating the need for physical brushes.

3. What are the advantages of brushless motors over DC motors?

Brushless motors have higher efficiency, longer lifespan, and lower maintenance needs compared to DC motors. They also have a higher power-to-weight ratio and can operate at higher speeds and torque.

4. How do I control the speed and direction of a DC or brushless motor?

DC motors can be controlled by varying the voltage or current, while brushless motors require a more complex electronic speed control system to adjust the timing and amplitude of the current to the different motor phases.

5. Can DC and brushless motors be used interchangeably?

While both types of motors can perform similar tasks, they are not interchangeable. The control systems and power sources are different, and the mechanical design of the motor is also optimized for its specific type. However, brushless motors are becoming more popular and may eventually replace DC motors in many applications.

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