Linear Motors Application Guide
Stator of linear motor has a relatively strong magnetism, thus there will be some specific problems during application. Therefore, proper solutions to the problems are the key to success application, and the following aspects should be concerned in specific application:
Guarantee mounting dimension between active cell and stator
The gap between active cell and stator of linear motor is one important parameter, and any small changes can cause great changes of property of motor. Over big gap can directly affect output of linear motor; while over small gap can possibly cause damages to motor since it absorbs other things. Therefore, in installation, it must strictly control to guarantee normal operation of motor.
Reduce magnetic attraction force
Stator of linear motor has a strong magnetizability to ferromagnetic materials. Experiments indicated that normal magnetic attraction force of permanent magnet stator of linear motor is as big as about 10 times of the driving force continuously provided by motor, and magnetic attraction force of stator has nothing to do with whether active cell of motor powers on. Magnetic attraction force exists between stators and between stators and installation parts. Layout of single motor generally adopts a method of being parallel to track of parts. At that time, magnetic attraction force greatly increases bearing force of linear track and causes serious transformation, which will affect machining precision of numerically-controlled machine tool and greatly increase pressure between track and sliding block at the same time, thus increasing force of friction of sliding block and possibly generating trust ripple to affect dynamic performance of machine tool. Therefore, it is a prominent problem to decrease magnetic attraction force of motor reasonably.
Pay attention to anti-magnetism and anti-interference
Since magnetic field of linear motor is open, magnetic materials such as metal dust and powder are easy to be absorbed by magnetic field of motor and cannot operate normally, and they can even damage motor. Therefore, it is necessary to have magnetic separation treatment. In addition, it should also consider protection of cooling liquid, lubricating oil and cable of machine tool, masking processing of signal line, load interference and system control. Since linear motor drive system does not have the link of intermediate gearing, interference such as quality of work pieces and changes of cutting force can directly act on motor. Meanwhile, end effect of linear motor will also increase difficulty of system control, thus controller should have a strong capacity of resisting disturbance and favorable stability.
Solve the problem of heating
When linear motor is under working condition, energy loss of coil will generate a big quantity of heat. If space of the drive is small, temperature of active cell of motor will have a rapid increase, and since active cell is generally around the guide rail of machine, over high heat will cause great changes of temperature of guide rail of machine, and thus causing thermal transformation of guide rail and affecting working precision of the machine. Meanwhile, temperature rise of active cell will increase resistance value of internal coil winding. If the system needs to maintain the output, it certainly needs bigger current; and since there are more energy losses at the same time, which makes temperature rise higher, a vicious circle will be formed. Therefore, effective cooling measures must be adopted to control temperature within a reasonable range so as to guarantee normal application of motor.