High Power Brushless Motor
Brushless motors produce electrical power at all torque values and RPM. They need the correct switching sequence in the power circuit to obtain this. This can be implemented as discrete logic, or more commonly a customised logic-gate array.
Brushed motors use a commutator, which makes sliding contacts with the rotor conductor windings. This causes friction, sparking and arching, limiting max RPM, increasing heat losses and reducing efficiency.
Efficiency
The lack of brushes means that brushless motors have higher efficiency than brushed motors. They are also typically smaller and lighter, so they can be used in applications where space and weight are limited. The automotive industry, for example, uses brushless motors to drive not just the vehicle’s propulsion systems but ancillary functions such as air conditioning and power steering.
A three phase brushless DC motor consists of a permanent magnet rotor and a stator wound with copper wire that creates electromagnetic poles, or winds. The electrical current from the motor controller drives these windings, and the interaction between the rotor’s magnetic field and the magnets in the stator causes the motor to rotate.
To test a high speed brushless motor’s efficiency, you can use a multimeter to measure the DC voltage and current flowing through the rotor and stator. Subtract the zero RPM power High power brushless motor draw to remove the motor controller switching losses, and then use the rest of the data to estimate core loss.
Core loss is caused by the magnetic polarization of the rotor’s permanent magnets being influenced by the windings in the stator, causing energy to be lost as heat. Core loss is also influenced by current ripple and higher-order harmonics, but these effects tend to be small in brushless DC motors. You can also use a FEA model to estimate core loss, but this process is less accurate and is not required for most testing purposes.
Noise
The rotor and stator of brushless motors produce significantly less noise than their brushed counterparts. Unlike brushed motors which use carbon or graphite brushes to rub against the commutator, brushless motors do not have any parts that can wear or create dust and noise.
The main source of electrical noise is sparking at the commutator, which occurs when the brushes lie in an unstable position on the commutator surface and the current is much higher than expected. Insulation formed on the commutator surfaces may also lead to electrical noise. These electrical noises can be reduced by adding capacitors or RC snubbers.
Mechanical noises from the internal components are another important factor to consider when selecting a high power brushless motor. Uncontrolled mechanical noise can degrade system performance and increase maintenance costs. It can also cause pressure injuries to people using handheld devices, which can be particularly dangerous in hospitals and other medical facilities.
Magnetic noise is generated when the magnetic field passes through a motor’s core and causes vibration. This type of noise tends to increase when the motor is under load.
To reduce magnetic noise, the manufacturer of the motor should optimize the stator and rotor design. This includes ensuring that the rotor shaft is accurately matched to the frame and that there are no gaps or looseness between the frame and the rotor core. The manufacturer should also test the rotor and frame for mis-machining and other imperfections that can produce vibrations.
Torque Ripple
Torque ripple is the variance in the torque produced throughout a motor’s rotation. It is caused by variations in the electromagnetic fields generated by the permanent magnets mounted on the rotor and the steel teeth of the stator laminations. Cogging torque also contributes to this variance. All electric motors, including slotless motors, produce this phenomenon. It cannot be completely eliminated because the brushes and commutator act as electrical switches that open and close, all at the same time, during the motor’s commutation sequence. This causes arcing at the brushes, which produces significant electrical noise that can be transmitted to sensitive circuits.
Advanced drives incorporate a technique called commutation control that reduces this voltage ripple to make the motor operate smoothly. However, the required drive capacity and associated cost are prohibitive in many high power applications.
This research aims to reduce the torque ripple in a high-power BLDC motor by applying a DC-link voltage boost control mode. In order to achieve this, the phase current waveforms (ia, ib, and ic) are controlled by the pulse pattern of the pulse generator. The zoomed-in waveforms of dynamic experimental results under a low speed operation condition are shown in Figure 12. In this case, it can be seen that the proposed method is effective in maintaining the stability of the non-commutation phase current and reducing commutation torque ripple.
Rotational Inertia
When a motor is rotating, it produces a moment of inertia due to its mass and dimensions. The smaller the mass and bigger the diameter of the motor, the less its moment of inertia will be. A lower ratio of load inertia to motor inertia will allow the motor to accelerate or decelerate more quickly. Load inertia can also be reduced by changing the gear ratio.
Brushed DC motors use electrical current to rotate a magnetic field in the High power brushless motor supplier stator and rotor. As the coils of the rotor’s electromagnetic poles are repelled by and attracted to the unlike poles in the fixed magnetic fields, they cause the rotor to rotate.
These motors have a very high moment of inertia and require a large starting voltage. They’re often used to drive fans and other small equipment with low power requirements.
Brushless DC motors are more expensive than brushed DC motors and require more complex electronics to control them. However, they have the advantage of higher efficiency, faster response time and longer battery run times than brushed motors. They are widely used in cooling fans, CD/DVD players and direct-drive turntables for gramophone records. They’re also found in cordless tools and electric vehicles. There are several types of brushless motors based on design, sensor use and power signal type. There are in-runner and out-runner designs, and a number of pole counts.