A, method of frequency control of motor speed: Frequency control of motor speed is to change the frequency of the motor stator power, to change its synchronous speed control method. Variable frequency speed regulation system is the main equipment to perkins diesel generator provide frequency conversion power inverter, frequency conversion motor can be divided into ac - dc - ac frequency converter and ac - ac frequency converter two kinds big, cross - straight - to pay inverter are mostly used in China at present. This method is suitable for the requirement of high precision, better speed control performance. Its characteristics: 1, high efficiency and speed control in the process of no additional loss; 2, wide application range, can be used in the cage type asynchronous motor; 3, large range of speed regulation, and the characteristics of hard, high precision; 4, complex technology, high cost, maintenance difficulties. Second, the change pole logarithmic speed control methods: This control method is used to change the stator winding of red way to change the speed cage motor stator polar logarithmic to achieve. This method is suitable for don't need a stepless speed www.facebook.com/dongfeng.motor regulation of production machinery, such as metal cutting machine tools, elevators, lifting equipment, fan, water pump, etc. Characteristics are as follows: 1, with a hard mechanical properties, good stability; 2, no slip loss, high efficiency; 3, simple wiring and convenient control, low price; 4, have used differential is bigger, cannot obtain smooth speed regulation; 5, can be used with regulating speed control, electromagnetic slip clutch, smooth speed characteristics of high efficiency. Three, cascade speed regulation method: Cascade speed regulation refers to the motor rotor winding circuit in series with adjustable additional potential to change the slip of the motor, to achieve the purpose of speed control. Most of the slip power is absorbed by series of additional potential to recycle produce additional device, the absorption of returning the slip power grid or conversion of energy use. According to the slip power utilization way, cascade speed regulation can be divided into motor ac motor electric 65kw cascade speed regulation, mechanical cascade speed regulation and thyristor cascade speed regulation form, adopts thyristor cascade speed regulation. This method is suitable for the fan, water pump and the rolling mill, mine hoist, the extrusion machine use. Its characteristics are: 1, but will slip loss in the process of speed feedback to the grid or production machinery, high efficiency; 2, unit capacity is proportional to the speed range, saving investment, apply to speed range in production machinery from 70% to 90% of the rated speed; 3, speed regulating device failure can switch to run at full speed, avoid production; 4, thyristor cascade speed regulation low power factor, harmonic impact is bigger. Four, the stator voltage regulating speed control methods: Change of motor stator voltage, be able to get a different set of mechanical characteristic curve, in order to gain different speed. Due to the torque of the motor and the voltage is proportional to square, thus maximum torque decreased a lot, the smaller range of speed regulation, and makes difficult to apply general squirrel-cage motor. In order to enlarge the speed range, regulating speed rotor resistance value should be adopted for the big cage motor, such as torque motor, USES for regulating speed or frequency on the wound rotor motor series resistor. In order to expand the stable operation range, speed above 2:1 Settings when feedback control should be adopted to achieve automatic adjustment speed. Regulating speed control is a main device can provide voltage change of power supply, the current commonly used ways with saturable reactor in series voltage regulator, autotransformer and thyristor voltage regulation. Thyristor voltage regulation mode is the best. Regulating speed generally applicable to the production machinery under 100 kw. Regulating speed control features: 1, the pressure regulating speed control circuit is simple, easy to realize automatic control; 2, in the form of heat transfer differential pressure regulating process power consumption in the rotor resistance and low efficiency. Five, the wound rotor motor rotor series resistance speed control methods: Wound rotor asynchronous motor rotor string into the additional resistance, make the slip of the motor, motor under low speed running. The series resistance, the greater the lower the speed of the motor. This method is simple, easy to control, but the slip power consumption in the form of heat on the resistance. Step speed, mechanical properties of soft.