Brake motors, also known as holding brake motors, are increasingly widely used in the equipment manufacturing industry (for equipment with a Z-axis). Based on its experience in promoting and applying brake motors in recent years, Leadshine Intelligent provides a systematic introduction to the application knowledge of brakes for motors.
I. Structure and Principle of Electrically Excited Brakes
1.1 Structure of Electrically Excited Brake
In the 1950s, Lenze introduced a dry, double-sided, power-off-activated, spring-loaded electromagnetic safety brake, which quickly became popular in Germany and was imitated by other countries. Its structure mainly consists of a stator and a rotor. The stator contains wound coils encapsulated in epoxy resin. The rotor is made of a specific friction-resistant material. The frictional torque between the rotor and stator is generated by the pressure of circumferentially distributed springs, which clamp the rotor between the armature and a plate. See the diagram below:
1.2 Working principle of electrically excited brake
The rotor is mounted on the servo motor shaft via a rotor hub, while the stator or plate is fixed to the end cover. When the coil is not energized, the armature is held in place by a compressed torque spring, and the rotor is clamped between the armature and the plate. The resulting friction brakes and holds the servo motor shaft in place. In this state, a certain gap is maintained between the stator and the armature. When the coil is energized, magnetic flux is generated, forming a closed magnetic circuit between the stator and the armature. The stator overcomes the compression force of the torque spring and attracts the armature. Simultaneously, the rotor becomes free, and the rotating shaft is released, as shown in the diagram below.
1.3 Installation Requirements for Electrically Excited Brakes
Rotor hub fixing
Ensure the rotor hub does not come into contact with the armature or stator, and secure it to the shaft with Allen screws. When applying adhesive to the Allen screws, be careful not to leave any adhesive on the rotor hub surface.
Bolts and screws
For bolts and screws used in brake installation, please use adhesive to prevent loosening and ensure tightness.
axis
Please set the shaft tolerance to h7 grade (JIS B 0401). Also, please note that the higher the hardness of the material used for the shaft, the worse the tightening effect of the hex socket screws.
Precision of brake mounting surface
Please note the coaxiality (X) between the embedded part and the shaft, and the perpendicularity (Y) between the brake mounting surface and the shaft must not exceed the allowable value.
1.4 Usage and Environmental Requirements of Electrically Excited Brakes
wire
Do not pull the brake cable forcefully, bend it excessively, or lift the cable by hand.
Environment, friction surface
Dry brakes must be used when the friction surfaces are dry; do not allow water or oil to come into contact with them. Water or oil on the friction surfaces will cause a decrease in torque, and dry brakes must be covered with a protective cover.
Operating ambient temperature
The operating ambient temperature is -10℃ to +40℃. If the temperature exceeds this range, please consult the manufacturer.
power supply voltage
Excessive fluctuations in power supply voltage can affect brake performance. The power supply voltage is allowed to fluctuate within ±10% of the rated voltage.
1.5 Circuit protection for electrically excited brakes
When a DC excitation current is applied to an electrically excited brake, energy accumulates in the coil. If the current is then interrupted, the accumulated energy will generate a surge voltage across the coil. This surge voltage can sometimes exceed 1000V depending on factors such as the interruption speed and interruption current, potentially causing coil damage and burnt-out contacts of the switching devices. Therefore, it is necessary to install an appropriate discharge circuit to prevent these faults.
Leadshine recommends connecting an 82V varistor in parallel with a 24V power supply brake for current bleed. Alternatively, a transient suppression diode can be connected in reverse across the brake power supply terminals. See the diagram below:
It has the effect of significantly suppressing surge voltage and has less armature release time lag.
It has a great effect in suppressing surge voltage, but the armature release time is delayed, making it unsuitable for high-frequency holding brake applications.
1.6 Advantages and disadvantages of electrically excited brakes
advantage
A. It can reach 100% of the rated torque in the initial stage of operation, without the need for break-in or trial operation.
B. Long service life, made of wear-resistant and highly abrasion-resistant materials, durable and long-lasting.
C. It is cheaper than permanent magnet brakes.
D. Compared to permanent magnet brakes, it generates more heat.
shortcoming
Compared to permanent magnet brakes, it generates more heat.
Leadshine Intelligent's open-loop stepper motors, such as the 57HS22-S and 86HSB85E, utilize electrically excited brakes from a renowned Japanese brand. Closed-loop stepper motors, such as the 57HBM20-BZ-1000 and 86HBM80-BZ-1000, employ electrically excited brakes from a well-known Taiwanese brand. Our assembly process has been refined over many years, resulting in a complete product line with stable and reliable quality. We look forward to your purchase. If you require other models of brake motors, please call our hotline at 400-885-5521.
II. Structure and Principle of Permanent Magnet Brake
2.1 Structure of Permanent Magnet Brake
Its structure is shown in the figure below; it mainly consists of two parts: the stator and the rotor. The stator mainly consists of a stator support, permanent magnets, a frame, enameled wire, epoxy potting compound, and friction functional surfaces. The rotor mainly consists of friction materials such as aluminum bushings and armatures.
2.2 Working principle of permanent magnet brake
The permanent magnet brake rotor is mounted on the servo motor shaft via a rotor bushing; an armature is placed on the rotor aluminum plate; the armature and aluminum plate are assembled together using riveting and other processes, with a spring sandwiched between them. (This type of spring only stretches axially and does not rotate, as shown in the figure below.) The stator support is designed with high-temperature resistant rare-earth permanent magnets, an insulating frame, and copper wire coils wound on the frame.
When DC current is applied to the stator enameled wire, the magnetic field formed is opposite in polarity to the magnetic field of the permanent magnet, and the magnetic circuit cancels out, the rotor armature is released and can rotate freely; when the stator coil is de-energized, only the permanent magnet remains in the stator to form a single magnetic circuit, which attracts the rotor armature, and the friction between the rotor armature and the friction surface of the stator generates a holding torque.
2.3 Installation of Permanent Magnet Brake
Due to the strong magnetism of the stator, the installation environment requires high precision; metal dust and burrs must not adhere to the friction surface. The air gap must be adjusted manually and controlled within the allowable range to achieve optimal performance. The installation process is relatively complex (the air gap of electrically excited brakes is pre-adjusted at the factory).
The recommended installation method is internal mounting, as shown in the diagram above. The inner ring of the rear bearing serves as the axial mounting reference surface for the rotor, while the outer ring of the bearing serves as the mounting reference surface for the stator. The air gap must be controlled within the allowable range, therefore, high consistency in the radial and axial movement of the bearing is required. The clearance between the rotor and stator needs to be controlled using a plug gauge; generally, a clearance of 0.2mm is required.
2.4 Advantages and disadvantages of permanent magnet brakes.
advantage
A. The permanent magnet brake exhibits no slippage in both static holding braking and dynamic starting braking states;
B. It can completely avoid the "disc rubbing" phenomenon of spring-loaded brakes, reduce noise and motor heat generation, and is suitable for higher speed motors;
C. Compact structure and high torque;
The response time is faster than that of electrically excited brakes;
shortcoming
A. The power supply has positive and negative poles and must not be connected incorrectly, otherwise the magnetic circuit will be reversed and it will not work properly;
B. The installation process is relatively complex.
C. The manufacturing process is complex, and the price is higher than that of spring brakes.
Leisai's intelligent AC servo motors, including the ACM6004L2G-A0-B-SS, ACM6004L2G-B0-D-SS, and ACM8008M2G-B1-D-SS, utilize permanent magnet brakes from a renowned domestic brand. These brakes are internally mounted, dustproof, oil-proof, and waterproof. They feature excellent air gap consistency and a stable and reliable installation process. We look forward to your purchase.
III. Comparison between electrically excited brakes and permanent magnet brakes
Leadshine intelligent brake motors cover three series: stepper, closed-loop, and servo. With extensive experience in selection, installation, and application, you can purchase with confidence and enjoy Leadshine's comprehensive one-stop service. Hotline: 400-885-5521. We look forward to your call.
Regarding Lei Sai
Leadshine's motion control product series mainly includes digital stepper drivers, stepper motors, simple servo systems, AC servo systems, digital DC servo systems, integrated motors, multi-axis PCI motion control cards, stand-alone motion controllers, and dedicated CNC systems. These products have been widely used in automation equipment across hundreds of industries, including electronics, robotics, machine tools, lasers, medical, textiles, packaging, and advertising. Since its inception, Leadshine has helped tens of thousands of equipment manufacturers in various industries successfully implement motion control solutions. According to authoritative statistics, Leadshine has become the largest supplier of stepper drivers and small-to-medium power servo products in China in terms of production and sales volume. Its products are exported to more than sixty countries and regions, including the United States, Germany, the United Kingdom, India, Singapore, Hong Kong, and Taiwan. Due to its stable and reliable product quality and excellent reputation, Leadshine has become an internationally renowned brand in the motion control industry.
