The calculation is too many factors and complicated. You can look up a table or use an empirical formula to estimate the total current first and choose the wire based on the current.
1mm2x8A=8A ?2.5 mm2 BVV copper conductor safe load capacity of the recommended value of 2.5 × 8A/mm2 = 20A ?4 mm2 BVV copper conductor safe load capacity of the recommended value of 4 × 8A/mm2 = 32A?
You 3KW about 6A current, the copper core wire is not less than a minimum of 1mm2 line, it is recommended that you use a 1.5mm2 line. If you use aluminum core wire it is recommended to upgrade with 2.5mm2 wire.
1) drive motor can be divided into: electric tools (including drilling, polishing, grinding, slotting, cutting, reaming and other tools) with electric motors, home appliances (including washing machines, electric fans, refrigerators, air conditioners, tape recorders, VCRs, video recorders, video disk players, vacuum cleaners, cameras, hairdryers, electric shavers, etc.) with electric motors and other general-purpose small machinery and equipment (including a variety of small machine tools, Small machinery, medical equipment, electronic instruments, etc.) with electric motors.
2) control motor is divided into: stepping motor and servo motor.
5. According to the structure of the rotor can be divided into: cage induction motor (the old standard called squirrel cage asynchronous motor) and wire-wound rotor induction motor (the old standard called wire-wound asynchronous motor).
6. According to the operating speed can be divided into: high-speed motor, low-speed motor, constant-speed motor, speed motor. Low-speed motor is divided into gear motor, electromagnetic reduction motor, torque motor and claw pole synchronous motor.
Speed motor can be divided into step constant speed motor, stepless constant speed motor, step variable speed motor and stepless variable speed motor, but also can be divided into electromagnetic speed motor, DC speed motor, PWM frequency conversion speed motor and switched reluctance speed motor.