LAFERT motors, German LAFERT models, LAFERT prices

LAFERT motors consist of the motor body and the driver, representing a typical mechatronic product. A brushless motor refers to a motor without brushes and a commutator (or slip rings), also known as a commutator-less motor. As early as the nineteenth century, when motors were first invented, the practical motors produced were of the brushless type, namely AC squirrel-cage asynchronous motors, which were widely used. However, asynchronous motors have many insurmountable defects, resulting in slow development of motor technology. Transistors emerged in the mid-twentieth century, leading to the emergence of DC brushless motors that use transistor commutation circuits to replace brushes and commutators. This new type of brushless motor is called an electronically commutated DC motor, which overcomes the defects of the first generation of brushless motors.

LAFERT motor fault troubleshooting

Motor winding ground fault, 1, Fault symptoms: live casing, loss of control circuit control, winding short-circuit heating, causing the motor to fail to operate normally. 2, Causes: winding dampness causing decreased insulation resistance; long-term overload operation of the motor; corrosion by harmful gases; metal foreign objects entering the winding interior and damaging insulation; insulation damage touching the iron core when rewinding the stator winding; winding ends touching the end cover or base; stator and rotor friction causing insulation burnout; lead wire insulation damage contacting the casing; overvoltage (such as lightning strike) causing insulation breakdown. 3. Inspection methods: (1) Visual inspection. Observe the winding ends and insulation materials in the slots for damage and scorch marks; if present, these indicate the ground point. (2) Multimeter inspection. Use the low-resistance range of a multimeter; if the reading is very low, it indicates a ground fault. (3) Megohmmeter method. Select different megohmmeters according to the rating to measure the insulation resistance of each winding group. If the reading is zero, it indicates that the winding is grounded. However, for motor insulation dampness or breakdown due to accidents, judgment must be based on experience. Generally speaking, if the pointer fluctuates unstably at "0", it can be considered to have a certain resistance value. (4) Test lamp method. If the test lamp lights up, it indicates a winding ground fault. If sparks or smoke are observed at a certain location, that location is the winding ground fault point. If the lamp glows dimly, there is insulation breakdown to ground. If the lamp does not light up, but sparks appear when the test probe is grounded, it indicates that the winding has not broken down but is severely damp. You can also lightly tap the edge of the housing shoulder with a hard wood block; if the light flickers on and off at a certain spot, indicating intermittent current flow, that spot is the ground point. (5) Current burn-out method. Use a variable transformer. After connecting to the power supply, the ground point will heat up quickly, and the spot where the insulation smokes is the ground point. Pay special attention that for small motors, the current must not exceed twice the rated current, and the time must not exceed half a minute; for large motors, use 20%-50% of the rated current or gradually increase the current, and immediately cut off the power when the ground point just starts to smoke. (6) Group elimination method. For ground points inside the iron core with severe burning, where the burnt copper wire is fused with the iron core, the method is to divide the grounded phase winding into two halves, and so on, to finally locate the ground point. 4. Treatment methods: (1) If the winding ground is caused by dampness, dry it first. When cooled to around 60–70℃, apply insulating varnish and then dry again. (2) If the winding end insulation is damaged, re-insulate the ground point, apply paint, and then dry. (3) If the winding ground point is in the slot, rewind the winding or replace part of the winding components. Finally, measure with different megohmmeters to ensure technical requirements are met.

LAFERT motor applications

Static index terms for motors: Number of phases: the number of pairs of excitation coils that generate different pole pair N, S magnetic fields. Usually denoted by m. Beat count: the number of pulses or conduction states required to complete one periodic change of the magnetic field, denoted by n, or refers to the number of pulses required for the motor to rotate through one tooth pitch angle. Taking a four-phase motor as an example, the four-phase four-beat operation mode is AB-BC-CD-DA-AB, and the four-phase eight-beat operation mode is A-AB-B-BC-C-CD-D-DA-A. Step angle: the angular displacement of the motor rotor corresponding to one pulse signal, denoted by θ. θ = 360 degrees / (rotor teeth J * operating beats). Taking conventional two-phase and four-phase motors with 50 rotor teeth as an example: in four-beat operation, the step angle is θ = 360 degrees / (50 * 4) = 1.8 degrees (commonly known as full step); in eight-beat operation, the step angle is θ = 360 degrees / (50 * 8) = 0.9 degrees (commonly known as half step). Detent torque: the locking torque of the motor rotor itself when the motor is not energized (caused by harmonics of the magnetic field tooth shape and mechanical errors). Static torque: the locking torque of the motor shaft when the motor does not rotate under rated static excitation. This torque is the standard for measuring motor volume (geometric dimensions) and is independent of drive voltage and drive power supply. Although static torque is proportional to the electromagnetic excitation ampere-turns and related to the air gap between the stator teeth and the rotor, excessively reducing the air gap and increasing excitation ampere-turns to improve static torque is not advisable, as this will cause motor heating and mechanical noise.

LAFERT motor braking methods

Motor braking: Users often confuse the functions of electromagnetic braking, regenerative braking, and dynamic braking, resulting in the selection of incorrect accessories. Dynamic brakes consist of dynamic braking resistors and shorten the mechanical feed distance of servo motors through energy consumption braking during faults, emergency stops, or power outages. Regenerative braking refers to the process where the servo motor feeds the energy generated during braking back to the DC bus through the inverter circuit during deceleration or stopping, where it is absorbed by the RC circuit. Electromagnetic braking locks the motor shaft via a mechanical device. Differences among the three: (1) Regenerative braking only works when the servo drive is operating normally; it cannot brake the motor during faults, emergency stops, or power outages. Dynamic brakes and electromagnetic brakes do not require power to operate. (2) Regenerative braking operates automatically by the system, whereas dynamic brakes and electromagnetic brakes require external relay control. (3) Electromagnetic brakes are generally activated after SV and OFF; otherwise, amplifier overload may occur. Dynamic brakes are generally activated after SV, OFF, or main circuit power-off; otherwise, the dynamic braking resistor may overheat.

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