1. Pole change speed regulation
This speed regulation method is to change the number of stator pole pairs of the cage motor to achieve the speed regulation intention by changing the wiring method of the stator winding, and the characteristics are as follows: it has hard mechanical characteristics and good stability; No slip loss, high power; The wiring is simple, the operation is convenient, and the price is low. There is a step-by-step speed regulation, and the gradation difference is large, and the slippery speed regulation cannot be obtained; It can be used in conjunction with voltage and speed regulation and electromagnetic slip clutch to obtain higher power smooth speed regulation characteristics. This method is applicable to production machinery that does not require stepless speed regulation, such as metal cutting machine tools, lifts, lifting equipment, fans, water pumps, etc.
Second, frequency conversion speed regulation
Frequency conversion speed regulation is a speed regulation method that changes the frequency of the stator power supply of the motor and then changes its synchronous speed. The primary equipment of the frequency conversion speed regulation system is the frequency converter that supplies the frequency conversion power supply, and the frequency converter can be divided into two categories: communication-DC-communication frequency converter and communication-communication frequency converter. Its characteristics: high power, no additional loss in the process of speed regulation; It has a wide application scale and can be used for cage asynchronous motors; The speed regulation scale is large, the characteristics are hard, and the precision is high; The technology is messy, the cost is high, and the protection and maintenance are difficult. This method is suitable for occasions that require high precision and good speed regulation performance.
3. Cascade speed regulation
Cascade speed regulation refers to the intention of adding adjustable additional electric potential into the rotor circuit of the wound motor to change the slip of the motor and achieve the intention of speed regulation. Most of the slip power is absorbed by the additional potential that is connected in series, and then the additional equipment is used to return the absorbed slip power to the grid or convert the energy for use. According to the slip power absorption method, cascade speed regulation can be divided into motor cascade speed regulation, mechanical cascade speed regulation and thyristor cascade speed regulation, and thyristor cascade speed regulation is mostly selected, which is characterized by: the slip loss in the speed regulation process can be fed back to the power grid or production machinery, and the power is higher; The capacity of the equipment is proportional to the speed regulation scale, the investment is saving, and it is suitable for the production machinery with the speed regulation scale in the additional speed of 70%-90%; When the speed control equipment fails, it can switch to full speed operation to prevent production stopping; The power factor of thyristor cascade speed regulation is low, and the harmonic influence is greater. This method is suitable for use in fans, water pumps, rolling mills, mine hoists, and kneading machines.
Fourth, the rotor string resistance speed regulation of the wound motor
The rotor of the wound asynchronous motor is connected with additional resistance, so that the slip rate of the motor increases, and the motor operates at a lower speed. The greater the resistance of the series, the lower the rotational speed of the motor. This method is simple and easy to operate, but the slip power is consumed on the resistor in the form of heat. It is a step-by-step speed regulation, and the mechanical characteristics are soft.
5. Stator pressure and speed regulation
When the stator voltage of the motor is changed, a set of different mechanical characteristic curves can be obtained, and then different speeds can be obtained. Since the torque of the motor is proportional to the square of the voltage, the maximum torque decreases a lot, and the speed regulation scale is small, which makes it difficult to apply the general cage motor. In order to expand the scale of speed regulation, a cage motor with a large rotor resistance value should be used for voltage and speed regulation, such as a torque motor specially used for voltage and speed regulation, or a frequency resistor connected in series on a wound motor. In order to expand the scale of stable operation, when the speed regulation is more than 2:1, feedback control should be selected to achieve the intention of automatic speed adjustment. The primary equipment of voltage and speed regulation is a power supply that can supply voltage changes, and the commonly used voltage regulation methods include series full reactors, autotransformers and thyristor voltage regulation. The thyristor voltage regulation method is optimal. Characteristics of voltage and speed regulation: the circuit of voltage and speed regulation is simple, and it is easy to realize automatic control; In the process of voltage regulation, the slip power is consumed in the rotor resistance in the form of heat, and the power is low. Voltage and speed regulation are generally suitable for production machinery below 100KW.
6. Electromagnetic speed regulation motor speed regulation
The electromagnetic speed control motor is composed of three parts: cage motor, electromagnetic slip clutch and DC excitation power supply (controller). The DC excitation power supply is small and usually consists of a single-phase half-wave or full-wave thyristor rectifier, which can change the size of the excitation current by changing the conduction angle of the thyristor. The electromagnetic slip clutch is composed of three parts: armature, magnetic pole and excitation winding. The armature and the latter have no mechanical contact and are both able to roll freely. The coaxial connection between the armature and the rotor of the motor is called the active part, which is driven by the motor; The magnetic pole is docked with the load shaft with a coupling and is called the driven part. When both the armature and the magnetic poles are stopped, if the excitation winding is passed through DC, a number of pairs of magnetic poles with N and S polarity substitution will be formed along the circumferential surface of the air gap, and the magnetic flux passes through the armature. When the armature rotates with the dragging motor, due to the relative motion between the armature and the magnetic pole, the armature induction occurs eddy current, and the eddy current and the magnetic flux interact with each other to produce torque, and the rotor with the magnetic pole is driven to rotate in the same direction, but its speed is always lower than the speed N1 of the armature, which is a differential speed regulation method, and the DC excitation current of the differential clutch can be changed by changing the DC excitation current of the differential clutch. The speed regulation characteristics of electromagnetic speed regulating motor: the equipment structure and control circuit are simple, the operation is reliable, and the maintenance is convenient; Smooth speed regulation, stepless speed regulation; No harmonic effect on the power grid; High speed loss and low power. This method is applicable to medium and small power, requiring slippery and smooth, short-term low-speed operation of production machinery.
7. Hydraulic coupling speed regulation method
Hydraulic coupling is a kind of hydraulic transmission equipment, which is generally composed of pump wheels and turbines, which are collectively called working wheels and are placed in a sealed housing. The shell is filled with a certain amount of operating liquid, when the pump wheel rotates under the drive of the prime mover, the liquid in it is driven by the blades and rotates, and when it enters the turbine along the outer ring of the pump wheel under the effect of centrifugal force, the turbine blades are thrusted on the same steering to drive the production machinery to operate. The power transfer capacity of the fluid coupling is the same as the relative amount of liquid in the shell. In the process of operation, changing the filling rate can change the turbine speed of the coupler, and the stepless speed regulation is carried out, which is characterized by: the power adapts to a large scale, and can meet the needs of different powers from tens of kilowatts to thousands of kilowatts; The structure is simple, the operation is reliable, the use and maintenance are convenient, and the cost is low; Small size, can accommodate large; Convenient operation and conditioning, simple automatic control, this method is suitable for fans, pumps.
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