1, what is a frequency converter? [1] Frequency converter is the use of power semiconductor devices on and off the role of the power frequency power supply to another frequency of electrical energy control devices, can realize the AC asynchronous motor soft start, frequency conversion speed regulation, improve the operating accuracy, change the power factor, overcurrent / overvoltage / overload protection and other functions. Domestic technology leading brands are Huichuan, Ou Rui (formerly Yantai Huifeng), three crystal, blue sea Huateng. 2, what is the difference between PWM and PAM? PWM is the English Pulse Width Modulation (Pulse Width Modulation) abbreviation, according to a certain law to change the pulse width of the pulse train, in order to regulate the output volume and waveform of a value-adjusting method. PAM is the English Pulse Amplitude Modulation (Pulse Amplitude Modulation) abbreviation, is to change the pulse amplitude of the pulse train according to a certain law, in order to regulate the output value and waveform of a modulation method. 3、What is the difference between voltage type and current type? The main circuit of inverter can be roughly divided into two categories: voltage-type is to transform the DC of voltage source into AC inverter, and the filtering of DC circuit is capacitor; current-type is to transform the DC of current source into AC inverter, and the filtering of DC circuit is inductor. 4、Why does the voltage of inverter change proportionally with the frequency? The electromagnetic torque of any motor is the result of the interaction of current and magnetic flux, and the current is not allowed to exceed the rated value, otherwise it will cause the motor to heat up. Therefore, if the magnetic flux decreases, the electromagnetic torque must also decrease, resulting in lower load carrying capacity. From the formula E=4.44*K*F*N*Φ, it can be seen that in frequency conversion speed control, the magnetic circuit of the motor changes in a fairly large range with the operating frequency fX, which is very easy to make the magnetic circuit of the motor seriously saturated, resulting in serious distortion of the waveform of the excitation current and generating a spike current with a very high peak value. Therefore, the frequency and voltage should be changed proportionally, that is, change the frequency while controlling the output voltage of the frequency converter, so that the magnetic flux of the motor is maintained at a certain level, to avoid the generation of weak magnetism and magnetic saturation phenomenon. This control method is mostly used in fan and pump energy-saving inverter. 5、When the motor is driven by industrial frequency power supply, the current increases when the voltage drops; for inverter drive, if the voltage also drops when the frequency drops, does the current increase? When the frequency decreases (low speed), the current increases if the same power is output, but under the condition of certain torque, the current is almost unchanged. 6、What is the starting current and starting torque of the motor when running with frequency converter? When running with frequency converter, the frequency and voltage will be increased accordingly with the acceleration of the motor, and the starting current will be limited to below 150% of the rated current (125%~200% depending on the type of machine). When starting directly with industrial frequency power supply, the starting current is 6~7 times of the rated current, therefore, it will produce mechanical and electrical shock. The use of inverter drive can be started smoothly (starting time becomes longer). The starting current is 1.2~1.5 times of the rated current, and the starting torque is 70%~120% of the rated torque; for the frequency converter with automatic torque enhancement function, the starting torque is more than 100%, and it can be started with full load. 7、What is the meaning of V/f mode? When the frequency decreases, the voltage V also decreases proportionally, this question has been explained in Answer 4. The proportional relationship between V and f is pre-determined by considering the characteristics of the motor, usually there are several characteristics in the controller's memory device (ROM), which can be selected with a switch or a scale dial. 8. How does the motor torque change when V and f are changed proportionally? If the voltage is lowered proportionally when the frequency drops, the torque generated at low speeds tends to decrease because the AC impedance becomes smaller while the DC resistance remains unchanged. Therefore, given V/f at low frequency, the output voltage should be increased in order to obtain a certain starting torque, and this compensation is called enhanced starting. This compensation is called enhanced starting. It can be realized by various methods, such as automatic method, selecting V/f mode or adjusting potentiometer. 9、It is written in the instruction manual that the variable speed range is 60~6Hz, i.e. 10:1, so there is no output power below 6Hz? The power can still be output below 6Hz, but according to the temperature rise of the motor and the size of the starting torque and other conditions, the minimum frequency of about 6Hz, at which time the motor can output the rated torque without causing serious heating problems. The actual output frequency of frequency converter (starting frequency) is 0.5~3Hz according to the type of machine. 10、Is it possible to require a certain torque even if the combination of general motors is above 60Hz? Normally, it is not possible. Above 60Hz (there are also models above 50Hz), the voltage is unchanged, generally constant power characteristics, in the high-speed requirements of the same torque, we must pay attention to the selection of the motor and the inverter capacity. 11、What is the meaning of the so-called open loop? To use the motor device set speed detector (PG), the actual speed feedback to the control device for control, known as "closed-loop", without PG operation is called "open-loop". General-purpose inverters are mostly open-loop, but some models can be fed back by PG using an option. No speed sensor closed-loop control is based on the establishment of the mathematical model based on the flux of the motor's actual speed, equivalent to a virtual speed sensor to form a closed-loop control. 12、How to do when the actual speed deviates from the given speed? In open-loop, even if the frequency converter outputs the given frequency, when the motor is running with load, the speed of the motor varies within the range of the rated rotation rate (1%~5%). For the occasions which require high accuracy of speed regulation, and even if the load varies, the motor is required to run at a speed close to the given speed, the inverter with PG feedback function can be used (optional parts). 13、If the motor with PG is used, can the speed accuracy be improved after feedback? Inverter with PG feedback function can improve the accuracy. But the value of speed accuracy depends on the accuracy of PG itself and the resolution of inverter output frequency. 14、What is the meaning of stall prevention function? If the given acceleration time is too short, the output frequency change of inverter is much more than the change of rotational speed (electric angle frequency), the inverter will be tripped due to the flow of over-current and the operation stops, which is called stall. In order to prevent stalling the motor to continue to run, it is necessary to detect the size of the current for frequency control. When the acceleration current is too large, the acceleration rate is appropriately slowed down. The same is true for deceleration. The combination of the two is the stall function. 15, there are acceleration time and deceleration time can be given separately, and acceleration and deceleration time *** with the given models, what is the significance of this? Acceleration and deceleration can be given separately for the type of machine, for a short period of acceleration, slow deceleration occasions, or for small machine tools need to be strictly given to the production of beat time occasions is appropriate, but for the fan drive occasions such as acceleration and deceleration time are longer, acceleration time and deceleration time can be * * * with the given. 16、What is regenerative braking? If the command frequency is lowered during the operation of the motor, the motor becomes an asynchronous generator state operation and works as a brake, which is called regenerative (electrical) braking. 17. Is it possible to get more braking power? The energy regenerated from the motor is stored in the filter capacitor of the inverter, and the regenerative braking force of the general-purpose inverter is about 10%~20% of the rated torque due to the capacitor's capacity and voltage resistance. If adopt optional parts braking unit, it can reach 50%~100%. 18、Please explain the protection function of inverter? The protection function can be divided into the following two categories: (1) detecting the abnormal state and then automatically correcting actions, such as overcurrent stall prevention, regenerative overvoltage stall prevention. (2) Blocking the PWM control signal of the power semiconductor device after detecting an abnormality to stop the motor automatically. Such as overcurrent cutoff, regenerative overvoltage cutoff, semiconductor cooling fan overheating and instantaneous power failure protection. 19、Why does the protection function of frequency converter act when the load is continuously connected with the clutch? When connecting the load with clutch, at the moment of connection, the motor changes sharply from no-load state to the area with large turnover rate, and the large current flowing through causes the inverter to trip overcurrent and can not be operated. 20, in the same plant large motors together, running inverter will stop, why is this? When the motor starts, the starting current corresponding to the capacity will flow through the motor stator side of the transformer generates a voltage drop, the motor capacity is large when this voltage drop also has a large impact, connected to the same transformer on the inverter will make a judgment of the undervoltage or instantaneous stop, and thus sometimes the protection function (IPE) action, resulting in the stopping of the operation. 21、What is inverter resolution? What is the significance? For digital control inverter, even if the frequency command is an analog signal, the output frequency is also given in levels. The smallest unit of this level difference is called frequency conversion resolution. Frequency resolution is usually taken as 0.015~0.5Hz. For example, if the resolution is 0.5Hz, then the top of 23Hz can be changed to 23.5, 24.0 Hz, so the motor action is also followed by a level. This causes problems for applications such as continuous winding control. In this case, if the resolution is about 0.015 Hz, it is possible to adapt to a 4-stage motor with a step difference of 1 r/min or less. In addition, there are some models where the given resolution is not the same as the output resolution. Is there any restriction on the installation direction when installing the inverter? Inverter internal and back structure considering the cooling effect of the upper and lower relationship to the ventilation is also important, therefore, for the unit type in the disk, hanging on the wall are taken longitudinal position, as far as possible, vertical installation. 23, do not use soft start, will the motor directly into a fixed frequency inverter can? In a very low frequency is possible, but if the given frequency is high with the industrial frequency power supply direct starting conditions are similar. Will flow over the large starting current (6 ~ 7 times the rated current), due to the inverter cut off the overcurrent, the motor can not start. 24、What should be paid attention to when the motor is running over 60Hz? More than 60Hz operation should pay attention to the following matters: (1) machinery and devices running at that speed to be fully possible (mechanical strength, noise, vibration, etc.). (2) The motor enters the range of constant power output, and its output torque should be able to maintain the work (fans, pumps, and other shaft output power increases proportionally to the cube of the speed, so attention should be paid to a small increase in speed). (3) The life of the bearings should be fully considered. (4) For more than medium-capacity motors, especially 2-pole motors, in 60Hz or more operation should be carefully discussed with the manufacturer. 25、Can an inverter drive a geared motor? Depending on the structure of the gearhead and the lubrication method, a number of issues need to be noted. In the structure of the gear can usually be considered 70 ~ 80Hz as the maximum limit, the use of oil lubrication, continuous operation at low speeds is related to gear damage and so on. 26、Can inverter be used to drive single-phase motor? Can I use single-phase power supply? Basically, it cannot be used. For the governor switch starting single-phase motor, in the working point below the speed range will burn the auxiliary winding; for capacitor starting or capacitor operation mode, will induce capacitor explosion. The power supply of inverter is usually 3-phase, but for small capacity, there are also single-phase power supply operation. 27. How much power is consumed by the inverter itself? It is related to the type of inverter, operation status, frequency of use, etc., but it is difficult to answer. However, the efficiency of the inverter below 60Hz is about 94%~96%, according to which the loss can be projected, but the built-in regenerative braking type (FR-K) inverter, if the braking loss is also taken into account, the power consumption will become larger for the design of the operating panel must be paid attention to. 28、Why can't it be used in 6~60Hz continuous operation in the whole area? General motor using the shaft mounted on the external fan or rotor end ring on the blade for cooling, if the speed is reduced, the cooling effect decreases, and thus can not withstand the same heat with high-speed operation, must reduce the load torque at low speeds, or the use of large-capacity frequency converter and motor combination, or the use of special motors. 29、What should be noted when using motors with brakes? Brake excitation circuit power should be taken from the input side of the inverter. If the brake operates when the frequency converter is outputting power, it will cause over-current cutoff. So the brake should be operated after the inverter stops output. 30、I want to use inverter to drive the motor with capacitor for power factor improvement, but the motor does not move, please explain the reason. The current of inverter flows into the capacitor for improving power factor, and it can't start because its charging current causes overcurrent (OCT) of inverter, as a countermeasure, please remove the capacitor and then run it, even to improve power factor, and it's effective to connect the AC reactor on the input side of inverter. 31、How long is the life of inverter? Although the inverter is a static device, there are consumable devices like filter capacitors and cooling fans, and if they are regularly maintained, it can be expected to have a life of more than 10 years. 32、The inverter has a cooling fan inside, what is the direction of the wind? What will happen if the fan is broken? For small capacity, there are models without cooling fan. With fan models, the wind direction is from the bottom up, so the place where the inverter is installed, the upper and lower parts should not be placed to hinder the suction and exhaust of mechanical equipment. Also, do not place parts that are afraid of heat above the inverter. When the fan fails, it is protected by the fan stop detection or the overheat detection on the cooling fan. 33. Filter capacitors are consumables, so how to judge its life? The electrostatic capacity of capacitors used as filter capacitors decreases slowly over time, and the life is judged by measuring the electrostatic capacity at regular intervals to 85% of the rated capacity of the product. 34、Is there any limitation on the installation direction when installing the inverter? Should be basically collected in the disk, the problem is the use of fully enclosed structure of the disk form factor is large, occupies a lot of space, the cost is relatively high. The measures are: (1) the design of the disk should be designed for the heat dissipation required by the actual device; (2) the use of aluminum heat sinks, wing coolant, etc. to increase the cooling area; (3) the use of heat pipes. In addition, the back of the inverter can be exposed type has been developed. 35、Want to increase the speed of the original conveyor belt to run at 80Hz, how to choose the capacity of the inverter? The power consumed by the conveyor belt is directly proportional to the rotational speed, so if you want to run at 80HZ, the power of both the inverter and the motor should be increased proportionally to 80HZ/50HZ, i.e., the capacity should be increased by 60%. Precautions for maintenance and inspection are: (1) After turning off the input power, wait at least 5 minutes before starting the inspection (also officially charging the light-emitting diode has been extinguished) Otherwise, it may cause electric shock. (2) Maintenance, inspection and part replacement must be carried out by competent personnel. (Remove all metal objects (watches, bracelets, etc.) and use tools with insulation protection before starting work) (3) Do not modify the frequency converter without authorization, otherwise it is easy to cause electric shock and damage to the product. (4) Before the frequency converter maintenance, must confirm whether the input voltage is wrong, will be 380V power supply into the 220V level inverter in the midst of the blow-up (blowing capacitors, varistors, modules, etc.). The inverter is mainly composed of semiconductor components, so it is necessary to carry out daily inspections to prevent unfavorable working environments, such as temperature, humidity, dust, and vibration, and to prevent other failures caused by the service life of the components. Inspection items: (1) Daily inspection: Check whether the inverter works as required. Use a voltmeter to check the input and output voltages of the inverter while it is working. (2) Periodic inspection: Check all areas that can only be checked when the inverter is stopped. (3) Parts replacement: The life of parts is largely related to installation conditions.
Edit this paragraph inverter working principle
Overview
The main circuit is to provide the asynchronous motor to regulate the voltage and frequency conversion power supply part, the main circuit of the frequency converter can be divided into two categories[1]:Voltage-type is the voltage source of DC converted to AC frequency converter, DC circuit filtering is capacitive. The current type is an inverter that converts the DC of the current source into AC, and its DC loop filter is an inductor. It consists of three parts, the "rectifier" which converts the industrial frequency power into DC power, the "leveling circuit" which absorbs the voltage pulsation generated in the converter and inverter, and the "inverter" which converts the DC power into AC power. inverter" which converts DC power to AC power.
Rectifiers
Recently, diode rectifiers have been used in large numbers to convert an industrial-frequency power supply into a direct-current power supply. Two sets of transistorized converters can also be used to form a reversible converter, which allows regenerative operation due to its reversible power direction.
Flat Wave Circuit
In the rectified DC voltage of the rectifier, there is a pulsating voltage of six times the frequency of the power supply, and the pulsating current generated by the inverter also makes the DC voltage change. In order to suppress voltage fluctuations, inductors and capacitors are used to absorb the pulsating voltage (current). When the capacity of the device is small, if there is a surplus of power supply and main circuit components, the inductor can be omitted and a simple flat wave circuit can be used.
Inverter
Contrary to the rectifier, the inverter converts the DC power to AC power at the required frequency, and the 3-phase AC output can be obtained by making the 6 switching devices conductive and turn off at the determined time. The switching time and voltage waveforms are shown as an example for a voltage type pwm inverter. The control circuit is the circuit that provides control signals to the main circuit of the asynchronous motor power supply (voltage and frequency adjustable), which has the frequency and voltage "operation circuit", the "voltage and current detection circuit" of the main circuit, the "speed detection circuit" of the motor, the "speed detection circuit" of the motor, and the "control circuit" of the main circuit. It consists of an "arithmetic circuit" for frequency and voltage, a "voltage and current detection circuit" for the main circuit, a "speed detection circuit" for the motor, a "drive circuit" to amplify the control signals of the arithmetic circuit, and a "protection circuit" for the inverter and motor. (1) Operational circuit: Compares the external commands such as speed and torque with the current and voltage signals of the detection circuit to determine the output voltage and frequency of the inverter. (2) Voltage and current detection circuit: detects voltage and current in isolation from the main circuit potential. (3) Driving circuit: the circuit that drives the main circuit devices. It is isolated from the control circuit to make the main circuit device on and off. (4) Speed detection circuit: The signal from the speed detector (tg, plg, etc.) mounted on the shaft of the asynchronous motor is the speed signal, which is fed into the operation circuit, and according to the instruction and operation, the motor can be made to run at the instructed speed. (5) Protection circuit: The voltage and current of the main circuit are detected, and when an abnormality such as overload or overvoltage occurs, the inverter is stopped or the voltage and current values are suppressed in order to prevent damage to the inverter and the asynchronous motor. [2]
Edit the role of the inverter
The background of the birth of frequency conversion technology is the widespread demand for stepless speed regulation of AC motors. The traditional DC speed control technology is limited in application due to its large size and high failure rate. □ After the 1960s, power electronic devices commonly used thyristor and its upgraded products. However, their speed regulation performance is far from meeting the needs. □ Starting from the 1970s, the research on pulse width modulation variable voltage variable frequency (PWM-VVVF) speed regulation has made a breakthrough, and the improvement of microprocessor technology after the 1980s has made it possible to implement various optimization algorithms easily. □ In the mid-to-late 1980s, the VVVF inverter technology in developed countries such as the United States, Japan, Germany and Britain was made practical, and commodities were put into the market and widely used. The earliest inverter was probably developed by the Japanese who bought the British patent. However, the United States and Germany with the advantages of electronic component production and electronic technology, high-end products quickly seize the market. □ stepped into the 21st century, the gradual rise of domestic inverter, has gradually seized the high-end market Unit series inverter This is a circuit topology developed only in recent years, it is mainly composed of input transformer, power unit and control unit three major components. Modular design, due to the use of power units in series with each other to solve the problem of high voltage and named, can be directly driven by the AC motor, without the need for output transformers, not to mention the need for any form of filter. The whole set of inverter *** has 18 power units, each phase by 6 power units in series, and form a Y-shaped connection, direct drive motor. The circuit and structure of each power unit are identical and can be interchanged or used as standby for each other. The input part of the frequency converter is a phase-shifting transformer, the original side of the Y-shaped connection, the secondary side of the triangle along the edge of the connection, *** 18 vice three-phase windings, respectively, for each power unit power supply. They are equally divided into three main parts, I, II and III, each part having 6 pairs of small three-phase windings with a uniform phase shift of 10 degrees between them. The characteristics of this inverter are as follows: ① The output voltage waveform is close to sinusoidal waveform by adopting multiplexed PWM control. ② Multiplication of rectifier circuits with up to 36 pulses, high power factor and small input harmonics. ③ Modular design, compact structure, easy maintenance, enhanced product interchangeability. ④ Direct high voltage output, no output transformer required. ⑤ Extremely low dv/dt output, without any kind of filter. ⑥ Fiber optic communication technology is adopted to improve the anti-interference ability and reliability of the product. (vii) Automatic bypass circuit of power unit, which can realize the function of no shutdown in case of failure. With the rapid development of modern power electronic technology and computer control technology, it promotes the technical revolution of electrical transmission. AC speed control instead of DC speed control, computer digital control instead of analog control has become the development trend. AC motor Frequency control is a major means to save power, improve production process, improve product quality, and improve the operating environment. Frequency conversion speed control is recognized as the most promising speed control method both at home and abroad for its high efficiency, high power factor, and excellent speed control and starting and braking performance. Previously, the high-voltage frequency converter, by the silicon controlled rectifier, silicon controlled inverter devices such as composition, many shortcomings, harmonics, on the power grid and motor have an impact. In recent years, the development of some new devices will change the status quo, such as IGBT, IGCT, SGCT and so on. The high-voltage inverter composed of them has excellent performance and can realize PWM inverter or even PWM rectifier. Not only has the harmonic small, power factor also has a great degree of improvement.
Edit the classification of the inverter
Unit series inverter
This is a circuit topology developed only in recent years, it is mainly composed of input transformer, power unit and control unit three major components. Modular design, due to the use of power units in series with each other to solve the problem of high-voltage and named, can directly drive the AC motor, without the need for output transformers, not to mention any form of filter. The whole set of inverter*** has 18 power units, each phase by 6 power units in series, and form a Y-shaped connection, directly drive the motor. The circuit and structure of each power unit are identical and can be interchanged or used as standby for each other. The input part of the frequency converter is a phase-shifting transformer, the original side of the Y-shaped connection, the secondary side of the triangle along the edge of the connection, *** 18 vice three-phase windings, respectively, for each power unit power supply. They are equally divided into three main parts, I, II and III, each part having 6 pairs of small three-phase windings with a uniform phase shift of 10 degrees between them. The characteristics of this inverter are as follows: ① The output voltage waveform is close to sinusoidal waveform by adopting multiplexed PWM control. ② Multiplication of rectifier circuits with up to 36 pulses, high power factor and small input harmonics. ③ Modular design, compact structure, easy maintenance, enhanced product interchangeability. ④ Direct high voltage output, no output transformer required. ⑤ Extremely low dv/dt output, without any kind of filter. ⑥ Fiber optic communication technology is adopted to improve the anti-interference ability and reliability of the product. (vii) Automatic bypass circuit of power unit, which can realize the function of no shutdown in case of failure. With the rapid development of modern power electronic technology and computer control technology, it promotes the technical revolution of electrical transmission. AC speed control instead of DC speed control, computer digital control instead of analog control has become the development trend. AC motor Frequency control is a major means to save power, improve production process, improve product quality, and improve the operating environment. Frequency conversion speed control is recognized as the most promising speed control method both at home and abroad for its high efficiency, high power factor, and excellent speed control and starting and braking performance. Previously, the high-voltage frequency converter, by the silicon controlled rectifier, silicon controlled inverter devices such as composition, many shortcomings, harmonics, on the power grid and motor have an impact. In recent years, the development of some new devices will change the status quo, such as IGBT, IGCT, SGCT and so on. The high-voltage inverter composed of them has excellent performance and can realize PWM inverter and even PWM rectifier. Not only has the harmonic small, power factor also has a great degree of improvement.
Categorized by the link of the transformation
(1) AC-Direct-Across inverter, it is the first frequency AC through the rectifier into DC, and then DC converted into frequency and voltage adjustable AC, also known as indirect frequency converter, is currently widely used general-purpose inverter. (2) can be divided into AC-AC inverter, that is, the industrial frequency AC is directly converted into frequency and voltage adjustable AC, also known as direct inverter;
Classified according to the nature of the DC power supply
(1) Voltage inverter Voltage inverter is characterized by the use of intermediate DC link of the energy storage element of the large capacitors, the reactive power of the load will be buffered by it, the DC voltage is relatively smooth, the DC power source of internal resistance is smaller than the voltage source, so it is equivalent to the voltage source, so it is widely used general-purpose inverter. Smaller, equivalent to the voltage source, so it is called voltage-type inverter, often used in the load voltage change occasions. (2) Current-type inverter Current-type inverter is characterized by the intermediate DC link using a large inductor as the energy storage link, buffer reactive power, i.e., choke current changes, so that the voltage is close to the sinusoidal waveform, due to the DC internal resistance is larger, so it is called the current source type inverter (current type). The characteristic (advantage) of current type inverter is that it can choke the frequent and sharp change of load current. Often used in the load current changes in the occasion.
According to the main circuit working method
Voltage type inverter, current type inverter
Categorized according to the principle of operation
Can be divided into V/f control inverter, rotational frequency control inverter and vector control inverter etc.;
Categorized according to the switching mode
Can be divided into PAM control inverter, PWM control inverter and high load frequency PWM control inverter. frequency converter and high-load frequency PWM control frequency converter;
Categorized according to the use
can be divided into general-purpose frequency converter, high-performance special frequency converter, high-frequency frequency converter, single-phase frequency converter and three-phase frequency converter and so on. In addition, the inverter can also be classified according to the output voltage regulation, classified according to the control mode, classified according to the main switching components, and classified according to the high and low input voltage.
By inverter voltage regulation method
PAM inverter is a kind of output control by changing the amplitude of voltage source Ud or current source Id. The PWM inverter method generates a pulse wave in one cycle of the inverter output waveform, and its equivalent voltage is sinusoidal with a smoother waveform.
By working principle
U/f control frequency converter (VVVF control), SF control frequency converter (rotational difference frequency control), VC control frequency converter (Vectory Control vector control)
By international regional classification
Domestic inverter; European and American inverters, Japanese inverters, South Korean inverters, Taiwan inverter , Hong Kong inverter
Classification by voltage level
High voltage inverter, medium voltage inverter, low voltage inverter [5]
Inverter energy saving effect
Inverter energy saving is mainly manifested in the application of fans and pumps. In order to ensure the reliability of production, a variety of production machinery in the design of the power drive, have left a certain amount of surplus. When the motor can not run at full load, in addition to meet the power drive requirements, the excess torque increases the consumption of active power, resulting in a waste of electrical energy. Fans, pumps and other equipment, the traditional speed control method is to adjust the inlet or outlet of the baffle, the valve opening to adjust the amount of air and water, its input power, and a large amount of energy consumption in the baffle, the valve in the interception process. When using frequency conversion speed control, if the flow requirements are reduced, by reducing the speed of the pump or fan can meet the requirements. By fluid mechanics, P (power) = Q (flow) × H (pressure), flow Q and speed N is proportional to the primary, pressure H and speed N is proportional to the square, the power P and speed N is proportional to the cube, if the pump's efficiency is certain, when the requirements of the regulation of the flow rate down, the speed of the speed of the N can be proportional to the decline in the power output of the shaft at this time P set up a square relationship between the decline. That is, the pump motor power consumption and speed approximate the relationship between the establishment of the square ratio. The team when the required flow Q is reduced, the frequency converter output frequency can be adjusted so that the motor speed n proportionally lower. At this time, the power of the motor P will be reduced significantly by the cubic relationship than adjusting the baffle, valve energy saving of 40% to 50%, so as to achieve the purpose of power saving. Ltd. to produce the frequency converter applied to the fan pump type load energy-saving examples: a centrifugal pump motor power of 55 kilowatts, when the speed down to the original speed of 4 / 5, the power consumption of 28.16 kilowatts, power 48.8%, when the speed down to the original speed of l / 2, the power consumption of 6.875 kilowatts, power 87.5%. 2, power factor compensation energy saving reactive power not only increases line loss and equipment heating, more importantly, the power factor reduction leads to a reduction in the active power of the grid, a large amount of reactive energy consumed in the line, the use of equipment is inefficient, a serious waste of the use of frequency conversion speed control device, due to the role of the inverter internal filtering capacitors, which reduces the reactive power loss, increasing the active power of the power grid. 3, soft start energy saving motor hard start on the power grid caused by serious impact, but also on the power grid capacity requirements are too high, the start of the large current and vibration generated by the baffle and the valve damage is very great, on the equipment, the service life of the pipeline is extremely unfavorable. And the use of frequency conversion energy-saving devices, the use of inverter soft start function will make the starting current from zero, the maximum value does not exceed the rated current, reducing the impact on the power grid and the requirements of the power supply capacity, extending the service life of equipment and valves. Save the maintenance cost of the equipment