1 magnetic brake magnetic brake structure schematic is easy to wear, the brake pad after wear will gradually reduce the braking effect, so always replace the brake pad 3 according to statistics in the above production situation, the average of each lathe every two The brake pads will be replaced once a week, but there are more than 20 devices. Because the device is difficult to assemble and disassemble, frequent replacement will inevitably affect the normal production order, so in the production with high braking efficiency requirements. It is not suitable for use.
2 reverse connection (ie reverse power supply) braking principle circuit diagram as shown.
The process is to first disconnect the three-phase positive power supply (1KM open) of the motor, and then pass the power supply with different phase sequence (2KM closed), that is, reverse the power supply, which changes the direction of the rotating magnetic field. status.丨3Mj due to inertia, the speed can not be V sudden, and the electromagnetic torque is negative by the positive change reverse braking principle, the rotor will decelerate rapidly under the combined action of electromagnetic torque and negative load torque. The direction of the moment and the speed are opposite. When the rotor is completely stopped, the power should be cut off, otherwise the motor will start running in reverse. The advantage of this method is that the braking effect is obvious, and the structure is simple and easy to implement, but the disadvantage is that the accuracy is poor, it is difficult to accurately control the braking time, the motor is reversely started, and the braking current is very high during braking. Large, the resistor must be connected in series in the main circuit. If the operation time is too long and the brakes are too frequent, the resistance will easily blow off due to the heat. In addition, the strong and sudden reverse action of the braking torque can cause a large impact, which is likely to cause greater mechanical damage to the transmission mechanism. Therefore, this method is not applicable. This is the brake device on the original lathe, and the structure is as shown. The armature 2 is fastened to the pulley 1 of the electric motor. On the one hand, the motor is slowed down due to the power cut-off speed. On the other hand, the electromagnetic coil 3 is turned on at this moment, and the yoke is generated by the alternating current, and the yoke is operated by a strong yoke. The pulley is firmly sucked so that the spindle can quickly stop. The armature 2 and the brake pad 4 function to better absorb and brake. After braking, the solenoid is de-energized and the pulley returns to a free state, ready for the next start. This is a commonly used braking method on the lathe, especially for ordinary lathes, because of its good braking effect, low power loss, and the replacement of the brake pads after the brake fails, without affecting the use of the motor at all. life. However, it can only be applied to occasions with low production efficiency, such as manual operation of ordinary lathes. For very frequent cases, when the spindle speed is high and the moment of inertia is large, the brake pads will be very energy-consuming. Show. When braking the energy consumption, first disconnect the stator winding from the three-phase AC power supply (IKM open), and then immediately pass a low-voltage DC power supply to the stator winding (2KM i closed DC power supply through the stator winding, after the internal energy consumption of the motor The brake principle circuit diagram establishes a fixed magnetic field. As the rotor continues to rotate under the mechanical energy stored in the motion system, an induced potential and current are generated in the rotor conductor. The current interacts with the constant magnetic field to generate the direction of action and the actual rotation of the rotor. In the opposite direction of the braking torque, under its action, the motor speed drops rapidly. At this time, the mechanical energy stored in the motion system is converted into electrical energy by the motor. G is consumed in the resistance of the rotor circuit. Based on the attempt and exploration of the K time, it is concluded that When braking, the turbulence of the stator winding is UC55V. The effect is better than the braking time, the motor heating, and the service life: the braking time is about 4.5 seconds. By setting the current value of the P winding A/=15A, although this value exceeds its rated current value, the braking time of the corpse is not enough. The current /y is greater than the rated current of the stator/, and can be taken as (23). When the braking system is used, the system can quickly decelerate in the combined action of the braking torque and the load torque, and it can stop accurately, unlike the reverse connection system. If the power is turned off in time, the motor will be reversed. In the latter stage of braking, as the speed decreases, the braking torque of the energy consumption is also reduced rapidly, so the braking is smoother, but the braking effect is better than the reverse. Due to the contradiction between the braking effect and the service life of the motor, the braking effect must be increased by increasing the winding current to increase the braking torque, but the current is too large, exceeding its use. The standard will cause the winding to generate heat and burn out. Therefore, the current of the general winding can not be too large, and the braking effect is correspondingly poor. In comparison, this solution is better than the first two, and the braking is accurate. It is stable and the failure rate is relatively low. If the braking effect is not too high, this method is still an economical and practical solution.
4 variable frequency start-up and brake asynchronous motor speed can be expressed by the formula of F-face: "for the speed, S is the slip ratio of the magnetic pole, / for the power supply frequency is fixed by the f motor load, so you want to get different The speed n can be achieved by changing the S, p, / / ​​three parameters 3, § n 1n condition 5? 1 is 4, can be established; and the magnetic pole logarithm is impossible: the only feasible condition is / ?0. Through the frequency / in the 1: change in the process to achieve different speeds called frequency control, frequency control in real life is a very common concept, from everyday home appliances to enterprise manufacturing The system is applied to the frequency conversion speed control technology. According to the power of the motor, we have selected the K-type frequency converter with the model FR-E540. The principle of the frequency conversion brake circuit is shown in the use. We have found that the frequency conversion brake has the following characteristics: accurate The frequency converter controls the time required for starting and braking by setting the parameters. It takes a certain time for the T lathe 7 to return to the cutting starting point from the origin or return from the cutting end point, and this time can be used. Electric For example, if the tool takes 1.8 seconds from the origin to the cutting start point, the start time parameter of the inverter can be set to 6 seconds. When braking, the tool takes 2 seconds from the return point after cutting. At this time, the braking time parameter of the inverter can be set to 2 seconds. It should be noted that the setting of the time must be based on the starting current and the braking current not exceeding the allowable range of the motor. The braking current is not equal to -r. The rated current of the motor is twice. The set time of the variable braking and the actual driving time is quite accurate, the deviation is small, and |:L is not affected by the temperature rise and the use time of the motor. The influence of the factors, so that the reliability of the automatic clamping of the workpiece on the la lathe is well ensured in the production, plays a key role in the automatic machining process of the production.
;Inverter forward rotation start reverse rotation) TI move ~ report transmission m connection input common terminal w4 frequency conversion brake circuit principle m start and brake process, the output voltage and output frequency of the inverter are linearly increasing and decreasing, and The frequency converter also provides large starting torque and braking S5 torque and sufficient low-speed torque through the control of the universal flux vector, so that the motor torque and speed can be coordinated and controlled at the start and braking moments and at the low speed. Achieve smooth start-up and braking. In particular, the improvement on the start-up completely solves the impact problem caused by the direct start of r. Because the starting and braking are the opposite modes of operation, and the rotation speed is abrupt, the repeated repeated impacts will inevitably cause great fatigue damage to the transmission mechanism. In severe cases, even gear breakage will occur. The use of the frequency converter greatly reduces the fatigue damage caused by the impact, and the entire transmission mechanism operates smoothly.
low noise. The inverter can change the flexible-PWM control of the motor audio through the parameter setting value. The flexible-PWM control changes the motor noise from the metal audio to the harmless synthetic audio, which greatly reduces the noise of the motor during the whole rotation process. .
Together with the smooth starting and braking characteristics, the lathe is smooth and quiet throughout the entire operation.
Less fever. When the braking time of the lathe is set to 2 seconds, the measured braking current does not exceed 9A, which is much lower than I5A when the brake is applied, and is lower than 20A when the brake is reversed. Due to the short braking time, The moving current is small, and the heat generation is inevitably greatly reduced. After 8 hours of operation, the measured motor temperature is only about 481, which fully meets the standard of use of the motor.
Under the same working time, the energy consumption braking should reach 60T: above, and the reverse braking should be higher.
(Continued to page 171) Output frequency (H/> Inverter output power Idj frequency special fk 1 'test. Bit value, 1 with the gap gap reduction is larger, which means that the small gap depends on the condition, The small gap leakage is not only affected by the gap value '丨, but also affected by the hydraulic element 丨t. its own shape tolerance and the eccentricity of the installation H process, so the actual position is used too small gap Value to solve the leakage problem 巳 no practical significance. 6. When the 丨k force is 10.0MK, 丨-y丨冬丨2 when /) 2.3mm, except for a few measurement points, the theoretical value is less than the test value, and the remaining wall points are The theoretical value is a large number of test values. As the gap value increases, the gap length decreases, and the gap is larger. The smallest gap in this test belongs to the mesoscale scale of the micron order, according to the gap without the juice and the geometric tolerance. The theoretical value of the laminar flow theory obtained from the leakage calculation formula has a small error with the experimental value. At this time, the theoretical value is smaller than the experimental value, which indicates that the laminar flow theory can be used to describe, and the possible reason for the error is. When the theoretical value of the leakage amount is calculated by using the formula (2), the influence of the eccentricity rate has been neglected, which causes a large error. It also shows that the eccentricity exists in this test and the theoretical value at the large gap value is larger than the experimental value. 5 times, this phenomenon cannot be explained by the same laminar flow theory as in the case of small gaps. The effect of the gap length on the leakage amount is not as obvious as the influence of the gap size, but the selection of its length has practical requirements for the practical application of the project. significance. From the test results, the leakage amount is inversely proportional to the length of the gap. The test results are close to the theoretical values ​​(except for A=0.0505, the gap is larger and the gap is smaller, the smaller the gap is, the fixed length Within the scope, the two are very close and the leakage is small. This shows that the population length has a direct impact on the leakage. In the fully developed laminar flow region, the effect of the gap length is consistent: 4 Conclusions The previous analysis can be It is concluded that (1) the influence of the ffi force on the leakage M is linear and seems to be affected by the size of the gap.
(2) Leakage collisions in the case of small gaps are mainly affected by the manufacturing and installation accuracy of hydraulic components. The sluice method for small gaps is explained by the S flow theory formula (1): (3) The influence of the gap length on the leakage M is inversely proportional. The larger the 丨t length, the smaller the gap. The K: metric is appropriately selected in the engineering practice. , that is, meet the engineering requirements
(Finish)
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