The Benefits of a Brushless DC Servo Motor
Servo motors are reliable tools that help foster an efficient operational landscape in diverse industry sectors. However, improper installation can have a negative impact on their lifespans.
A brushless DC servo motor does not require a commutator, which helps them convert electricity into mechanical power more efficiently. They also have a flat multi-pole design that minimizes audible noise and vibration.
High-Speed and Torque Capabilities
Compared to conventional brushed DC motors, brushless motors have higher torque and speed capabilities. This is due to the fact that brushless motors do not require the mechanical commutation points that transfer current between stationary electrical feed and rotating shaft. Instead, electronic commutation is used. This provides improved efficiency, high energy savings and superior control.
However, a brushless servo motor still requires feedback devices to control speed and position. These include encoders and position sensors, which are connected to the rotor via a sensor cable. This is necessary for smooth, quiet, precise motion. Allied Motion offers frameless, encoder-equipped, NEMA-size brushless servo motors in a variety of shaft diameters.
Hudson servo motors feature an obliquely aligned, permanent magnet rotor design that minimizes detent torque and produces harmonically-pure back-EMF for low-ripple torque. This brushless DC servo motor means the servo motors are able to achieve very smooth and accurate rotary positioning with a wide range of payloads.
Without brushes and commutators, a brushless servo motor has very low maintenance costs. Unavoidable wear only occurs in the bearings, so the motor can operate for longer and at higher speeds than brushed motors. Brushless servo motors are also more compact than their brushed counterparts. This allows you to integrate them into your application with ease and confidence. They also have very low noise and vibration.
Reliability
Brushless DC servo motors provide reliability and low electromagnetic noise, making them a smart choice for equipment control. They are easy to maintain, operate at a high power-to-weight ratio, and are smaller in size. They can be used in a wide range of industrial applications, including robotics. The lack of a commutator and brushes also eliminates sparks that could cause a fire hazard and reduces maintenance costs. They are also environmentally friendly since they do not use toxic materials such as lead or hexavalent chromium and are compliant with RoHS standards.
In brushless motors, an electronic sensor detects the rotor angle and controls semiconductor switches to reverse current flowing through the windings or, in some cases, turn off the electromagnets completely. This results in less friction and extends the motor’s working life compared to brushed motors.
Unlike brushless motors, brushed DC motors cannot perform a continuous operation without drive electronics because the brushes have to be constantly swapped in and out. The instantaneous switching of the brushes causes arcing and generates significant electrical noise that can interfere with sensitive electronics in the vicinity. This issue is often mitigated by using arc suppression circuits, but this can significantly reduce a motor’s operating efficiency and performance.
Longevity
In addition to their high-speed and torque capabilities, servo motors are highly efficient and durable. The fact that they do not use brushes means that they don’t wear down as quickly and need less maintenance. This allows them to provide reliable performance over long periods of time, even when operating under demanding conditions.
Incorporating components like absolute encoders enables the servo to retain position memory even after power is cut off, ensuring consistent operation and reliability. Additionally, integrating a feedback loop system enables the servo to detect and correct errors, enhancing performance consistency.
Brushless DC servo motors are available in hundreds of different sizes and at diverse prices, enabling you to find the right fit for your application. However, their advanced design and sophisticated electronics can also make them more expensive than brushed motors.
In addition, you’ll need to invest in additional equipment like sensors and an electronic controller. Furthermore, the wiring process must be completed by professionals to avoid incorrect connections that can have severe consequences for your project’s functionality. Conducting tests before integrating a servo motor into brushless motor controller full-scale operation can help you identify and address any issues before they become more serious.
Continuous Operation
Brushless DC motors can run continuously at higher speeds with less degradation of performance due to continuous contact between the brushes and commutator. The permanent magnets used in rotors of these motors also minimize rotational inertia, which allows for rapid acceleration and deceleration.
To control the servo motor, a drive with an “H-bridge” circuit that contains electronic switches (transistors, IGBTs, or MOSFETs) is used to generate pulse width modulated DC voltages to control the motor speed or torque. This control mechanism provides high efficiency, significant power savings, and superior control compared to the mechanical commutator and brushes of brushed DC motors.
Because of their fixed windings, brushless DC servo motors can be more compact than brushed motors with the same performance characteristics. This feature allows them to fit in tight spaces while still delivering adequate torque.
When choosing a brushless motor for an application, the actual AC power requirements must be sized appropriately for the system by determining the peak load requirement and using a safety factor to account for transformer voltage regulation. This conservatively sizing the motor and amplifier can reduce problems that arise from under sizing the combination and can help to extend the service life of the actuator by preventing thermal damage.
To minimize noise, a shielded motor cable should be used to connect the motor to its drive. This can be further improved by connecting a 250-VAX capacitor between one of the drive connections to block 50/60 Hz currents and to pass HF currents that are capacitively coupled from the motor coils to the frame.
