Permanent Magnet Brushless Direct Current Motors

The equivalent electrical circuit of a dc motor is shown in figure 5.2. It can be represented by a voltage source (Va) across the coil of the armature. The electrical equivalent of the armature coil can be described by an inductance (La) in series with a resistance (Ra) in series with an induced voltage (Vc) which

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Brushless motors are a bit similar to normal DC motors in the way that coils and magnets are used to drive the shaft. Though the brushless motors do not have a brush on the shaft which takes care of switching the power direction in the coils, and this is why they are called brushless. Instead the brushless motors have three coils on the inner (center) of the motor, which is fixed to the mounting. On the outer side it contains a number of magnets mounted to a cylinder that is attached to the rotating shaft. So the coils are fixed which means wires can go directly to them and therefor there is no need for a brush. The reason why QuadCopters use brushless motors instead of normal DC motors is the much higher speeds and less power usage for the same speed. The brushless motors are more efficient as there is no power lost as there is in the brush-transition on the DC motors. Usually rated with a KV rating (revolutions per volt). This is not equivalent to torque, but lower KV motors are usually used for larger

The electric motors work by electricity and magnets working together. Once the electricity gets going, the magnets take over. The magnets keep the motor going because the magnets used in motors have both positive and negative magnets on both sides. Surrounding the magnetic ends, are one positive and one negative magnet. This means that at any

Brushless DC motors are a vital part of the technology we use today in many different aspects of life; a common being computers. This essay will study how a brushless DC motor works, it’s pros, cons and how it compares to a brushed DC motor. Throughout will be various physics concepts and terms in order to provide the most accurate and detailed explanation.

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The design and build of simulation has two parts, part one is simulation of LED indicator for motor speed recognize and part 2 is simulation of V/F speed control of Linear induction motor. Firstly, design

Brushless DC motors is a kind of permanent magnate synchronous motor. Permanent magnet synchronous motors are classified on the basis of the wave shape of their induce emf, i.e, sinusoidal and trapezoidal. The sinusoidal type is known as permanent magnet synchronous motor (PMSM); the trapezoidal type goes under the name of PM Brushless dc (BLDC) machine. Table (2.1) shows the difference between (PMSM) and (BLDC) motor.

Direct current motors are used in many applications that require adjustable speed. In uses requiring quick stops, a dc motor can minimize the size of a mechanical brake or make it unnecessary. This is done by dynamic braking (motor-generated energy fed to a resistor grid), or by regenerative braking (motor-generated energy returned to the ac supply). DC motor speed can be controlled smoothly down to zero, followed immediately by acceleration

Abstract—This paper proposes direct torque control of induction motor simulation using conventional method and space vector pulse width modulation technique for ripple reduction. Direct Torque Control is a control technique used in AC drive systems to obtain high performance torque control and thereby controlling the speed of induction motor. The principle is based on simultaneous decoupling of stator flux and electromagnetic torque of AC drive system. DTC drives use hysteresis comparators and they suffer from high torque ripple and variable switching frequency problem. The proposed SVM based DTC reduces torque ripples. The basis of the SVM-DTC methodology is the calculation of the required voltage space vector to compensate the flux and torque errors and its generation using the SVM at each sample period. The performance of this method is demonstrated by simulation using MATLAB/Simulink software. Simulation results presented in this paper show the torque, flux linkage and stator current ripple decreases with the proposed SVM-DTC algorithm.

However, the problems are found in these motor for variable speed operation over last decades keeping technology growth in power semiconductors, microprocessors, adjustable speed drivers control schemes and permanent-magnet brushless electric motor production have been joined to enable reliable, cost-effective solution for a wide area of adjustable speed applications.

is the rotor resistor value and when the slip stays a very small value, then the s is also very small so it can be treat as a 0 value. is rotor induced EMF and it is in direct proportion to the voltage. Torque is in direct proportion to the s. Therefore, we know that torque T is also in direct proportion to . When we increase(decrease)the voltage supply, the torque will increase(decrease), therefore the speed increase(decrease). By changing the voltage supply we can achieve the speed control, this is the simplest way to control the speed. But not widely use in the real industry. Because: change a very large voltage but the speed only changes a little, the speed control range is too small. When the supply voltage has a sudden changing, the flux density in the motor, a sudden changing flus density will result a change in magnetic conditions of the motor. This result is not welcomed in the real condition of use. So changing the supply voltage is rarely used.[5][6]

Brushless motors are considered to be a high performance motor that is capable of providing large amounts of torque over a vast speed

The generation of the torque in the brushed DC motors is coming directly from the DC power. The internal commutation and the magnets that are stationary (magnets can be permanent or electromagnet) supply the power to the motor to generate the torque. These motors include carbon brushes to transfer the power to the rotating shaft.