How to choose the magnetic powder brake magnetic powder clutch
Magnetic powder clutches and brakes use magnetic powder under electromagnetic effects to transmit torque. They have the advantages of a linear relationship between the exciting current and the transmitted torque base, fast response speed, simple structure, no shock, no vibration, no noise, no pollution, etc. A multi-purpose automatic control element with excellent performance. It is widely used in various industries to control the loading and braking of machinery and the tension control of winding and unwinding in winding systems.
General application diagram (for tension control):
Unwinding: The unwinding tension is controlled by the braking torque of the magnetic powder brake in the unwinding device. As the winding diameter of the winding decreases, the braking torque must be continuously reduced. The tension detector is used in the figure. The tension of the winding is detected, and the torque of the magnetic powder brake is automatically controlled by the tension controller to make the tension constant.
Rewinding: The rewinding speed is normally faster than the linear speed of the material, so the magnetic powder clutch works in a slip state, and the tension is controlled by the torque of the magnetic powder clutch. In order to keep the tension constant, it must be increased or decreased according to the size of the coil. Torque of magnetic powder clutch.
Applications: paper industry, production of adhesive tapes, wire and cable manufacturing, packaging industry, paper processing, printing industry, film, film industry, textile industry, metal foil processing, rubber industry, fiber industry, gasoline engine, diesel engine running-in, Testing, loading in various tests, leather industry, fiber manufacturing, and other related coil processing industries.
The linear relationship between the exciting current and the torque: The torque of the magnetic powder brake and the magnitude of the exciting current are basically linear. By changing the magnitude of the exciting current, the size of the control torque can be arbitrarily adjusted.
Stable speed and torque characteristics
When the exciting current remains the same, the torque will be transmitted steadily without being affected by the speed change. This feature is used in tension control, and only needs to adjust the exciting current to accurately control the torque, so as to achieve the purpose of controlling tension.
Effective heat sink and its load characteristics:
Continuous sliding friction will inevitably generate heat. Magnetic powder clutches and magnetic powder brakes have complete heat dissipation devices. Among them, stator water cooling and stator rotor dual water cooling products can meet the needs of high power slip.
When the product's heat dissipation condition is constant, the maximum slip power allowed by the product is a fixed value, and its torque and speed can compensate each other within a certain range. Of course, neither the torque nor the speed can exceed its maximum.
Low control power:
Magnetic powder clutches and magnetic powder brakes use magnetic powder under electromagnetic effects to transmit torque. They can use a small amount of electric power to control a large amount of transmitted power. They can be easily controlled by electronic circuits and computers. They can be conveniently used in various industries. .
Fast response characteristics:
Magnetic powder clutches and magnetic powder brakes determine the non-response time, torque rise time and torque drop time of this product due to their inherent structural characteristics. This characteristic determines that magnetic powder clutches and magnetic powder brakes can be applied to frequent start and stop. , Commutation applications. Special needs can be improved by further optimizing the mechanical part and improving the loading power. Taking a 5kgm magnetic powder brake as an example, its non-response time is 25ms, and its torque rise and fall times are 270ms and 350ms, respectively.
When selecting magnetic powder clutches and brakes, it is necessary to calculate the torque, speed and slip power (heat generation) used, and confirm that all indicators are within the allowable range.
The selection methods and precautions for each item are explained below.
It is necessary to calculate the maximum and minimum values of the used torque and confirm whether the calculated value is within the controllable range. The magnetic powder clutch and brake torque can be controlled between the rated torque and the product idling torque * (0.1 to 100% of the rated torque). ※ Idle torque: Due to the loss of torque in the bearings and seals inside the product, even if the excitation current is set to 0A, the torque may not be 0N • m. This idling torque is usually about 0.1-2% of the rated torque, but it varies from product to product. )
The maximum speed, whether it is a magnetic powder clutch or a brake, needs to be controlled below the allowable speed. In addition, the minimum speed of the general magnetic powder brake should be controlled above 5-15r / min, and the difference between the input and output speed of the magnetic powder clutch needs to be set above 15r / min. When the magnetic powder clutch controls the winding tension, it must have a slip speed of more than 15 rpm, and the minimum slip speed should be controlled at 15-20 rpm. If the minimum slip speed is too large, the magnetic powder clutch may be heated.
The use of a lower speed will worsen the internal magnetic powder distribution, resulting in failure to obtain stable torque performance, or prolong the time required to reach the specified torque after starting. Large-sized magnetic powder brakes use low speeds and produce low-speed step crawling.
(3) Slip power (heat generation)
Because magnetic powder clutches and brakes are usually used in a continuous slip condition, the temperature of the magnetic powder clutches and brakes rises due to the heat generated by the slip. The temperature rise value is limited by the heat-resistant temperature of the parts used. Therefore, the allowable continuous slip power (allowable value of heat generation) is specified according to different models. That is, when operating within this allowable value range, the magnetic powder clutch and brake can be used in a stable state for a long time. On the contrary, if you exceed the allowable continuous slip power, the magnetic powder clutch and brake will be damaged. Please be careful.
Slip power (heat value) P (W) can be calculated by the following formula.
P = 0.105 × T × Nr (W)
T: torque (N • m);
Nr: slip speed (r / min) of magnetic powder clutch and brake.
(For magnetic powder clutch, it refers to the slip of input speed and output speed, and for magnetic powder brake, it means the input speed.)
选 Selection of magnetic powder brake magnetic powder clutch
Select the model of magnetic powder brake first according to the required maximum transmission torque value, the maximum speed is not greater than the use speed of the magnetic powder brake, the use speed of the magnetic powder brake is inversely proportional to the use torque, and then select the maximum slip power, such as the use of water The cooled magnetic powder brake needs to consider whether the specific use environment is allowed. If the maximum torque value of the magnetic powder brake can meet the requirements, but the slip power cannot meet the requirements, then a higher torque magnetic powder brake that meets the requirements must be selected. The heating of the magnetic powder brake is also related to the use time. If the use time is short, as long as a few minutes, the small slip power does not matter. If the water-cooled magnetic powder brake does not generate heat during use, it can also be used according to the specific situation. Do not cool down with water.
Magnetic powder brake Magnetic powder clutch has a variety of installation options, users can choose according to their needs.
Magnetic powder brake
• Single output shaft ultra-thin magnetic powder brake CZFB
• Vertical installation magnetic powder brake CZKL
• Single shaft magnetic powder brake (CZ type)
• Single shaft flange magnetic powder brake (CZF type)
• Hollow shaft flange type magnetic powder brake (CZK type)
• Double-outlet frame magnetic powder brake (CZS type)
• Hollow shaft ultra-thin magnetic powder brake (CZKB type)
• Hollow shaft housing rotating magnetic powder brake (CZKX type)
• Single-outlet miniature magnetic powder brake (CZW type)
Magnetic powder clutch
• Double-outlet frame magnetic powder clutch (CJ type)
• Double output shaft flange type magnetic powder clutch (CJF type)
• Hollow shaft housing rotating magnetic powder clutch (CJKX type)
• Double-outlet frame water-cooled magnetic powder clutch (CJS type)
• Natural cooling miniature magnetic powder clutch (CJW type)