The number of wires in the slot of a three-phase electric motor;
U c is the voltage of a single-phase network, V;
U is the nominal phase voltage of a three-phase motor, V.
Lower values of the coefficient are accepted for higher power motors (about 1 kW) with short-term and intermittent short-term operating modes.
Diameter (mm) of wire along the copper of the working winding
Where d is the diameter of the copper wire of a three-phase motor, mm.
The starting winding enters 1/3 of the groove.
The two most common types of starting windings are: with bifilar coils and with additional external resistance.
The winding with bifilar coils is wound from two parallel wires with different current directions (the inductive leakage resistance of bifilar windings is close to zero).
Where U c is the voltage of a single-phase network, V.
To obtain a large starting torque, preference should be given to poland telegram data the second version of the starting winding, since in this case the greatest starting torque can be obtained by changing the external resistance.
The current of a single-phase motor is determined by the calculated cross-section for the working winding and the current density in the winding of a three-phase motor I 1 = sp δ, where δ is the permissible current density (6-10 A / mm²).
Table. Product of cos φ and efficiency
If the motor power exceeds 500 W, the values of η and cos φ can be taken for three-phase asynchronous motors, reducing the power of a single-phase motor according to the formula above by 10-15%.
Example of converting a three-phase motor to a single-phase winding
Convert a three-phase motor into a single-phase winding. Electric motor power 0.125 kW, voltage 220/380 V, synchronous rotation frequency 3000 rpm; number of cores in the slot 270, number of stator slots 18. Wire brand PEV-2, copper diameter 0.355 mm, cross-section 0.0989 mm2. Set voltage of a single-phase motor 220 V.