What are the features and characteristics of single phase AC universal motor?
1.Features of single phase AC universal motors
Advantages:
1)can be used for both AC and DC ;
2)High speed,generally 400035000 RPM/Min;
3)Convenient speed regulation (voltage and speed regulation), and the speed has nothing to do with the power frequency;
4)The starting torque is large, 47 times the rated torque;
5)The mechanical characteristics are soft, and the overload capacity is strong;
6)The efficiency is generally 30 percent 70 percent ;
7)Small size and light weight;
Disadvantages:
carbon brushes and commutator wear, reversing sparks, electromagnetic interference, etc.
2.For 1 phase AC series motor,it has 4 characteristics under stable voltage and frequency
1)The relationship between current and torque: I=f(T), which is similar to a parabolic characteristic. If don't consider the influence of magnetic circuit saturation, T∝I2;
2)The relationship between current and speed: I=f(n), which is similar to a hyperbolic characteristic. When the power supply voltage is constant and the effect of magnetic circuit saturation is not considered, n∝(1/I);
3)The relationship between speed and torque: n=f(T). This characteristic curve is a soft characteristic;
4)The relationship between power factor and torque: COS(ф)=f(T), it is a straight line close to the level. The power factor of this type of motor is high, above 0.9, and the high-speed motor can be above 0.95;
In addition, the no-load speed of a single-phase series motor is theoretically infinite, so the no-load speed is very high. Therefore, the mechanical strength of the motor is usually taken into consideration, and no-load operation is not allowed for fear of "speeding." But in fact, due to the friction of the bearing, the pressure and friction of the brush, the wind friction of the armature and the demand for ventilation and heat dissipation, the armature is equipped with fan blades, which is equivalent to adding a small load to the motor, so the actual no-load speed is not It may be infinite. But the no-load speed is still relatively high, generally 1.5 to 3 times the rated speed, or even higher.
