Classification Of AC Three-phase Asynchronous Motor Windings

Single layer winding:
A single-layer winding is a winding in which only one coil effective edge is embedded in each stator slot, so its total number of coils is only half of the total number of slots in the motor. The advantage of single-layer winding is that it has fewer winding coils and the process is relatively simple; The utilization rate of the slot is improved due to the lack of interlayer insulation; Single layer structure will not experience phase to phase breakdown faults, etc. The disadvantage is that the electromagnetic waveform generated by the winding is not ideal, the iron loss and noise of the motor are large, and the starting performance is slightly poor. Therefore, single-layer winding is generally only used in small capacity asynchronous motors. Single layer windings can be divided into several winding forms, such as chain winding, cross chain winding, concentric winding, and cross concentric winding, according to the shape of their coils and the arrangement of their terminal parts.
1. Chain winding
Chain winding is composed of single-layer coil elements with the same shape and width, named after the fact that each coil at the end of the winding resembles a chain link. Special attention should be paid to the fact that the coil pitch of a single-layer chain winding must be odd, otherwise the winding will not be able to be arranged in a straight line.
2. Cross chain winding
When the number of slots in each pole and phase of the cross chain winding is an odd number greater than 2, the chain winding cannot be arranged, and a cross type winding with single or double coils is needed.
3. Concentric winding
Concentric windings surround all coils within the same pole phase group around the same center.
4. Cross type concentric winding
When the number of slots Q in each stage and phase is an even number greater than 2, a concentric winding form can be adopted.
The advantages of single-layer concentric winding and cross concentric winding are that the winding and embedding of the winding are relatively simple, while the disadvantage is that the coil end is too long and consumes too many wires. Except for occasional use in small capacity 2-pole and 4-pole motors, this winding form is rarely used nowadays.
Double-layer stacked winding
Single and double-layer hybrid winding
The relationship between star joints and corner joints
Star connection to corner connection: The total cross-sectional area of the wire diameter during the original star connection divided by 1.732 equals the total cross-sectional area of the wire diameter during the corner connection.
Corner connection to star connection: Multiplying the total cross-sectional area of the wire diameter at the original corner connection by 1.732 equals the total cross-sectional area of the wire diameter at the star connection.
The essential difference between star joints and corner joints
When connected to a star, the line voltage is equal to 1.732 times the phase voltage, and the phase current is equal to the line current.
When cornered, the phase voltage is equal to the line voltage, and the line current is equal to 1.732 times the phase current.
For motors of the same power, when connected in a star configuration, the wire diameter is thick and the number of turns is small, while when connected in an angle configuration, the wire diameter is thin and the number of turns is large.
The cross-sectional area of the corner joint is 0.58 times that of the star joint. (The total cross-sectional area of the wire diameter during corner connection divided by 0.58 equals the total cross-sectional area of the wire diameter during star connection. Multiplying the total cross-sectional area of the wire diameter during star connection by 0.58 equals the total cross-sectional area of the wire diameter during corner connection)
Formula for calculating cross-sectional area of wire diameter: cross-sectional area S=square of diameter multiplied by 0.785
The internal connections of a motor can be divided into salient and salient poles. The connection between salient and salient poles is determined by the design properties of the motor and cannot be changed
Calculation coefficient for no-load current of electric motor
Quadrupole and hexapole power factor 0.85-0.98.5
When the power factor is 0.85 and the efficiency is 0.85, the coefficient is 0.435, multiplied by the rated current
When the power factor is 0.86 and the efficiency is 0.86, the coefficient is 0.393, multiplied by the rated current
When the power factor is 0.87 and the efficiency is 0.87, the coefficient is 0.353, multiplied by the rated current
When the power factor is 0.88 and the efficiency is 0.88, the coefficient is 0.313, multiplied by the rated current
When the power factor is 0.89 and the efficiency is 0.89, the coefficient is 0.276, multiplied by the rated current
When the power factor is 0.90 and the efficiency is 0.90, the coefficient is 0.240, multiplied by the rated current
When the power factor is 0.91 and the efficiency is 0.91, the coefficient is 0.205, multiplied by the rated current
When the power factor is 0.92 and the efficiency is 0.92, the coefficient is 0.172, multiplied by the rated current
When the power factor is 0.93 and the efficiency is 0.93, the coefficient is 0.142, multiplied by the rated current
When the power factor is 0.94 and the efficiency is 0.94, the coefficient is 0.113, multiplied by the rated current
When the power factor is 0.95 and the efficiency is 0.95, the coefficient is 0.086, multiplied by the rated current
When the power factor is 0.96 and the efficiency is 0.96, the coefficient is 0.062, multiplied by the rated current
When the power factor is 0.97 and the efficiency is 0.97, the coefficient is 0.040, multiplied by the rated current
When the power factor is 0.98 and the efficiency is 0.98, the coefficient is 0.022, multiplied by the rated current
When the power factor is 0.99 and the efficiency is 0.99, the coefficient is 0.008, multiplied by the rated current
Four pole, six pole, eight pole power factor 0.81-0.85
When the power factor is 0.81 and the efficiency is 0.81, the coefficient is 0.468, multiplied by the rated current
When the power factor is 0.82 and the efficiency is 0.82, the coefficient is 0.433, multiplied by the rated current
When the power factor is 0.83 and the efficiency is 0.83, the coefficient is 0.398, multiplied by the rated current
When the power factor is 0.84 and the efficiency is 0.84, the coefficient is 0.365, multiplied by the rated current
When the power factor is 0.85 and the efficiency is 0.85, the coefficient is 0.332 multiplied by the rated current
Four pole, six pole, eight pole power factor 0.70-0.80
When the power factor is 0.70 and the efficiency is 0.70, the coefficient is 0.728, multiplied by the rated current
When the power factor is 0.71 and the efficiency is 0.71, the coefficient is 0.694, multiplied by the rated current
When the power factor is 0.72 and the efficiency is 0.72, the coefficient is 0.661, multiplied by the rated current
When the power factor is 0.73 and the efficiency is 0.73, the coefficient is 0.630, multiplied by the rated current
When the power factor is 0.74 and the efficiency is 0.74, the coefficient is 0.595, multiplied by the rated current
When the power factor is 0.75 and the efficiency is 0.75, the coefficient is 0.562, multiplied by the rated current
When the power factor is 0.76 and the efficiency is 0.76, the coefficient is 0.530, multiplied by the rated current
When the power factor is 0.77 and the efficiency is 0.77, the coefficient is 0.499, multiplied by the rated current
When the power factor is 0.78 and the efficiency is 0.78, the coefficient is 0.468, multiplied by the rated current
When the power factor is 0.79 and the efficiency is 0.79, the coefficient is 0.438, multiplied by the rated current
When the power factor is 0.80 and the efficiency is 0.80, the coefficient is 0.408, multiplied by the rated current
Six pole and eight pole power factor 0.75
When the power factor is 0.75 and the efficiency is 0.75, the coefficient is 0.496, multiplied by the rated current
Disassemble the stator core of the semi sealed motor: Use heating method to place the stator shell upside down and suspend it. When the temperature reaches a certain level, gently shake the stator shell and it will come out.
function:
The motor should be properly grounded, and there is a grounding screw in the lower right corner of the junction box. If necessary, the motor's foot or flange can also be used to fix the bolt for grounding.
The nameplate of the motor specifies star and triangle connections. In China, motors below 3kW use star connections, while motors above 3kW use triangle connections, and cannot be connected incorrectly.
Electric motors should generally be equipped with fault protection devices, such as thermal protection devices, motor electronic protectors, etc., and the setting value of the protection device should be adjusted according to the current on the motor nameplate. If the load of the motor is relatively stable, in order to better protect the motor, the setting value of the protection device can be adjusted according to the actual working current of the motor. The actual working current of the motor can be directly measured with a clamp ammeter when the motor is running under load.
When the voltage and frequency of the power supply deviate from the values on the nameplate by more than 5%, the motor cannot guarantee continuous output of rated power. Continuous operation of electric motors is not allowed to overload.
The motor should not produce intermittent or abnormal sounds or vibrations during no-load or load operation, and the bearing temperature should not be too high.