Lafert SpA motors, German Lafert SpA models, Lafert SpA prices

Lafert SpA motors refer to electric motors with a rated voltage above 1000V. Commonly used voltages are 6000V and 10000V. Due to differences in foreign power grids, there are also voltage levels of 3300V and 6600V. High-voltage motors were developed because motor power is proportional to the product of voltage and current. Therefore, when the power of low-voltage motors increases to a certain extent (such as 300KW/380V), the current is limited by the allowable carrying capacity of the wires, making it difficult to increase further or resulting in excessive costs. High voltage is required to achieve high-power output. The advantages of high-voltage motors are high power and strong shock resistance; the disadvantages are high inertia, making starting and braking difficult.

Lafert SpA motor classification

A shaded-pole single-phase motor is formed by embedding short-circuited copper rings or short-circuited coil groups in part of the stator poles. Shaded-pole single-phase motors include salient-pole and non-salient-pole types. When the stator winding is supplied with single-phase AC current, most of the pulsating magnetic flux generated couples directly to the rotor through the air gap, while a small portion of the flux induces magnetic flux when passing through the shaded-pole copper ring. This induced flux combines with the original flux and enters the rotor magnetic circuit through the air gap. According to Lenz's law, the induced flux always opposes changes in the original flux, and its phase lags behind the original flux. This creates two magnetic fluxes that are spatially displaced by a certain angle and have a phase difference, resulting in a rotating magnetic field with significant ellipticity. The rotation direction of a shaded-pole motor is fixed, moving from the unshaded part to the shaded part. These motors have low power, low starting torque, simple structure, low cost, and easy maintenance. Shaded-pole motors are generally used in small blower motors and fan motors.

Lafert SpA motor maintenance

Preparation and inspection before motor startup: Check whether the grounding of the electric and starting equipment is reliable and intact, and whether the wiring is correct and in good condition. Verify that the voltage and frequency indicated on the motor nameplate match the power supply voltage and frequency. For newly installed or long-idle motors, check the phase-to-phase and phase-to-ground insulation resistance of the windings before startup. The insulation resistance should be greater than 0.5 MΩ; if it is below this value, the windings must be dried. For wound-rotor motors, check whether the brush assembly on the slip rings operates properly and whether the brush pressure meets requirements. Check whether the motor rotates freely and whether the oil level in the sliding bearings reaches the specified level. Verify that the rated current of the fuses used for the motor meets requirements. Check whether all fastening bolts and mounting bolts of the motor are tightened. After all the above inspections meet the requirements, the motor can be started. After startup, run the motor under no-load conditions for about 30 minutes, and carefully observe whether there are any abnormalities. If abnormal conditions such as noise, vibration, or overheating are found, take corrective measures and only put the motor into operation after the issues are resolved. When starting a wound-rotor motor, connect the starting rheostat to the rotor circuit. For motors equipped with a brush-lifting mechanism, lower the brushes, disconnect the short-circuiting device, close the stator circuit switch, and adjust the rheostat. When the motor approaches its rated speed, lift the brushes, close the short-circuiting device, and the motor startup is complete.

Lafert SpA motor structure

The motor rotor consists of the rotor core, rotor winding, and shaft. The rotor core is also part of the motor's magnetic circuit and is made of stacked silicon steel sheets. Unlike the stator core laminations, the rotor core laminations have slots on the outer circumference. After stacking, the outer cylindrical surface of the rotor core uniformly forms many slots of the same shape to house the rotor winding. The rotor winding is another part of the induction motor circuit. Its function is to cut the stator magnetic field, generate induced electromotive force and current, and be subjected to force under the action of the magnetic field, causing the rotor to rotate. Its structure can be divided into two types: squirrel-cage winding and wound-rotor winding. The main characteristics of these two rotors are: squirrel-cage rotors have a simple structure, are easy to manufacture, economical, and durable; wound-rotor structures are complex and expensive, but external resistance can be introduced into the rotor circuit to improve starting and speed regulation performance. The squirrel-cage rotor winding consists of conductor bars placed in the rotor slots and end rings at both ends. To save steel and improve production efficiency, the conductor bars and end rings of low-power induction motors are usually cast in one piece from molten aluminum. For high-power motors, since the quality of cast aluminum is difficult to guarantee, copper bars are often inserted into the rotor core slots, and end rings are welded at both ends. The squirrel-cage rotor winding is self-closed and does not require an external power supply. Its shape resembles a cage, hence the name squirrel-cage rotor.

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