The windings of the stator can be arranged in star or Y or in delta. Steel rolling can be performed with or without grooves. A drill motor without grooves has a lower inductance. It can, therefore, operate faster and cause fewer ripples at lower speeds. Its major disadvantage is higher cost factors since it is necessary to multiply the windings to compensate for a larger airspace. The number of rotor poles may vary depending on the application. More poles increase the torque but reduce the maximum speed.
The material used to make the permanent magnets also has consequences on the maximum torque, which increases with the flux density. Since the switching must be performed electronically, the control of a brushless motor is much more complex than on the simple schemes associated with the brushed units.
Both analog and digital control methods are used. The basic control block is similar to that of brushed motors but a closed loop control is mandatory. Three main types of control algorithms are used on brushless motors: trapezoidal commutation, sinusoidal commutation and vector or field-oriented control.
Each control algorithm can be implemented in different ways depending on software coding and hardware design. Each offers specific advantages and disadvantages. Trapezoidal switching requires the simplest circuitry and control software making it an ideal solution for entry-level applications.
It uses a six-step process using rotor position feedback. Trapezoidal switching effectively controls the speed and power of the motor but suffers from torque ripple during switching, particularly at low speeds. Sensorless switching estimating the rotor position by measuring the back EMF of the motor provides impressive performance at the cost of greater complexity of the algorithm. By removing Hall effect sensors and their interface circuits, this sensorless switching reduces component and installation costs and simplifies system design.
This helps answer the question, what is a brushless motor? Brushless motor technology not only improves the power of your cordless power tools but also extends their working life. With these motors, you will have virtually no maintenance worries. The advantages of brushless technology are numerous. The absence of brushes eliminates problems associated with overheating and breakdowns. The service life of the brushless motor is therefore related only to the bearings.
The brushless motor is more compact and two to three times lighter than brushed units. This improves portability in addition to reducing vibration and noise.
So what exactly is the technology behind these new motors? A traditional brushed motor is made up of four basic parts: carbon brushes, a ring of magnets, an armature, and a commutator.
The magnets and brushes are stationary, while the armature and commutator rotate together on the motor shaft within the magnets. When the motor is energized, a charge travels from the battery, through the brushes, and into the commutator. The brushes are spring-loaded to maintain physical contact with the commutator. The commutator then passes the charge on to the armature, which is made up of copper windings they look like bundles of copper wire.
The windings are magnetized by the charge and push against the stationary ring of magnets that surround it, forcing the armature assembly to spin. The spin doesn't stop until the charge from the battery stops. A brushless motor loses the brushes and the commutator. And the locations of the magnets and windings are reversed: The magnets are on the conventional motor shaft and the copper windings of the armature are fixed and surround the shaft.
Instead of brushes and a commutator, a small circuit board coordinates the energy delivery to the windings. The brushes are spring-loaded into the commutator; they deliver the charge from the battery to the commutator.
Once the charge reaches the commutator, the commutator can then deliver it to the armature. The armature is a device composed of copper windings.
The armature is located next to the magnets, and these have an opposite charge than the copper. When the two charges collide, the motor turns, and the drill functions until the power current disappears. Brushless motors work differently. Instead of traditional parts, this device only uses magnets and an armature.
And rather than using carbon brushes and a commutator, when you squeeze the trigger on a brushless drill, the charge is sent from the battery to the armature through a circuit board. This makes for a smoother and faster connection than what you get with carbon brushes.
Cordless drills with brushless motors are taking over the market. By Perry Santanachote. Last updated: October 18, Sharing is Nice Yes, send me a copy of this email. Send We respect your privacy. Oops, we messed up. Try again later. When you shop through retailer links on our site, we may earn affiliate commissions. Learn more. Brushed vs. Brushless All cordless drills convert electricity into power by using the attracting and repelling actions of magnets to get the shaft spinning.
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