YASKAWA FM 054 Manual

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YASKAWA FM 054 Manual Manual pdf 45 page image

A DC motor is an engine for high-precision positioning. This consists of a fixed stator withpermanent magnets and a rotating armature. The current supply to the armature windinghappens by means of carbon brushes via the commutator as sliding contact. The indi-vidual armature windings are connected via the commutator, which serves as a polechanger. As soon as the armature winding is energized, a magnetic field builds up in thearmature. This results, influenced by the permanent magnets, in a rotational movement ofthe armature. Due to the rotation the commutator reverses the polarity in the armature. Inthis way the rotational movement is continued steadily. Controlling a DC motor by meansof pulse width modulation (PWM) is low-loss and has a high efficiency. With PWM, thestart and stop time of a square-wave signal is varied at a fixed base frequency of 32kHz.This results in different average voltages. When selecting a motor, the following factorsmust be considered:n Torque curve across the speedn Motor current across the speedn Winding resistance respectively motor inductancen The encoder respectively rotation encoder provides the controller with the position ofthe drive by means of digital signals. This can accordingly be evaluated by the PLC.n The encoder respectively rotation encoder supply a certain number of pulses per rev-olution.n The value generation is done by counting the pulses.For the requirements of the load to be moved and the consideration of additional loadssuch as bearings and gears, you can determine the necessary motor data. Here impor-tant parameters are:n Mass inertian Cycle times of positioningn Start, holding and torque at the maximum required speedn Acceleration and torque when passing through mechanical resonances e.g. whenusing mechanical memories as spring elements, vibration buffer or long drive belts.To avoid step losses, in accordance with the own inertia, the outputtorque of the engine should be greater than the determined mechanicaltorque.4.1.3 Encoder - signal evaluationn Incremental encoder are sensors for detecting angular or positional changes.n Depending on the sensor type and the desired resolution, the scanning happens bysliding contact, photo electrically or magnetically.– The scanning via sliding contact works in principle like a switch, which is mechan-ically operated.– With the optical scanning a disk, which has a fine raster, is optically scanned.– With the magnetic scanning a pole wheel or magnetic band is scanned which hasbeen written with a raster by a magnetization, before.n The incremental encoder has two sensors Track A and Track B for scanning.n The sensors are arranged at an angle of 90 degrees from each other on the systemto be scanned.MotorEncoderMechanicalSignal evaluationVIPA System SLIO DeploymentBasics > Encoder - signal evaluationHB300 | FM | 054-1CB00 | en | 18-06 45