| |
| Inverter (Variable-frequency Drive, VFD) is the application of frequency conversion technology and m |
| 1, what is the frequency?
Inverter power semiconductor devices is the use of the role of the off-frequency power conversion to another frequency power control device, can realize the AC asynchronous electrical
ABB converter
Machine soft starting, variable frequency speed regulation, improve operation accuracy, change of power factor, current / voltage / overload protection function.
What is the different point of 2, PWM and PAM?
PWM is the English Pulse Width Modulation (pulse width modulation) abbreviation, according to certain rules to change the pulse pulse width, to a modulation control output and waveform. PAM is the English Pulse Amplitude Modulation (pulse amplitude modulation) abbreviation, is according to a certain law change in the pulse rate pulse, to a modulation mode adjust output value and waveform.
What is the difference between the 3, the voltage type and current type?
The main circuit of inverter can be generally divided into two categories: voltage is DC voltage source inverter for AC, DC circuit is the filter capacitance; current model is the DC current source for AC inverter, the DC circuit filter inductance.
4, why the inverter voltage and frequency is proportional to the change?
Electromagnetic torque of any motor current and flux are the result of the interaction, the current is not allowed to exceed the rated value, otherwise it will cause the motor heating. Therefore, if the flux decreases, the electromagnetic torque will be reduced, resulting in lower load capacity.
By the formula of E=4.44*K*F*N* Φ can be seen, in frequency control, the motor magnetic circuit with fX operation frequency is varied over a considerable range, it is very easy to make the motor magnetic circuit saturation, leading to serious waveform distortion to the excitation current, produce peak current peak high
Therefore, the frequency and voltage proportional to change, and change frequency control inverter output voltage, the motor flux is maintained, avoid weak magnetism and magnetic saturation phenomenon. This means more control for the fan, pump energy-saving inverter.
5, the use of power frequency drive motor, voltage drop, current increases; for inverter drive, if the frequency has decreased, voltage drop, then the current is increased?
Decrease of frequency (low speed), if the same power output, the current increase in torque, but under certain conditions, current is almost invariant.
6, a transducer operation, the motor starting current, the starting torque?
Using frequency converter operation, with the motor to accelerate a corresponding increase in the frequency and voltage, the starting current is limited to 150% of the rated current following (according to a number of different, 125%~200%). Direct starting power, starting current and rated current is 6~7 times, therefore, will have an impact on the mechanical and electrical. Transducer transmission can be used to smooth start (starting time). The starting current is 1.2~1.5 times the rated current, the starting torque is 70%~120% rated torque; with automatic torque enhancement as a function of the frequency converter, the starting torque is more than 100%, can take full load starting.
7, V/f is what mean?
Frequency voltage V is proportional decline, in answering this question has 4. V and F ratio between the electrical characteristics and is considered a predetermined, usually in a storage controller (ROM) has several characteristics, can use the switch or dial to select.
8, according to the proportion of modified V and F, the torque changes in the electrical?
Frequency fully reduced in proportion to the voltage, then the exchange impedance and DC resistance unchanged, would have resulted in low speed and torque is reduced tendency. Therefore, when given in low frequency V/f, to make the output voltage to improve some, in order to obtain a start-up torque, such as enhanced compensation package. Can use various methods to achieve, the automatic methods, select V/f mode or adjust potentiometer method.
9, in writing on the manual transmission range 60~6Hz, namely 10:1, so in the following 6Hz no output power?
6Hz still in the following output, but according to the temperature rise of the motor and the starting torque conditions, the minimum frequency for about 6Hz, the motor rated output torque and the heat will not cause serious problems. The actual output frequency converter (frequency) according to the model of 0.5~3Hz..
10, the portfolio is in the general electrical 60Hz above also requires a certain torque, can?
Under normal circumstances, can not. In the above 60Hz (a 50Hz above model) voltage unchanged, a substantially constant power characteristic, require the same torque at high speed, must pay attention to the choice of motor and inverter capacity.
The 11, called the central mean?
Electrical devices used to speed detector (PG), the actual rotational speed control devices to control the feedback, called "closed loop", not PG operation is called "open loop". Central to the more generic transducer, and some types of aircraft can use the pieces for PG feedback. Speed sensorless closed-loop control method is based on the mathematical model established according to the actual speed of motor flux calculation, a closed-loop control is formed on a virtual speed sensor.
12, the actual rotational speed for a given rate of error, how to do?
Open loop, inverter output even given frequency, motor operation in a load, the speed of the motor slip in rated range (1%~5%) changes. The relatively high precision for governor, even if the load changes also required to set the pace in the near operation occasions, can function with PG feedback transducer (optional).
13, if the motor with PG, after feedback to improve the accuracy rate?
Frequency converter with PG feedback function, accuracy is improved. But the speed depends on the accuracy of Mr PG's accuracy and the inverter output frequency resolution.
14, stall prevent functional mean?
If given a short time to accelerate, transducer frequency changes far exceeds the output speed (Electrical angular frequency) changes, the frequency converter will be a flow of electric current and Tiaozha, stop functioning, which is called stall. To prevent stall makes the motor running, will be detected current size frequency control. When excessive speed up current accelerated rate due to slow. So when the speed of. The combination of the two is the stall function.
15, there is the acceleration time and deceleration time can be respectively given aircraft, and acceleration and deceleration time common given aircraft, the meaning?
Slowdown were to be added to the given models, for a short time to accelerate, slow deceleration occasions, is suitable or for small machine tools needed to set strict production time of the occasion, but for the fan drive and other occasions, acceleration and deceleration time is longer, the acceleration time and deceleration time can jointly given.
16, what is the regenerative braking?
The motor in operation in order to reduce the frequency of if, asynchronous electric motors into the generator operation state, while working as a brake, which is called regeneration (Electrical) brake.
17, whether you can get a larger braking force?
Electrical energy from renewable piling up in the filter capacitor inverter, due to the capacity of the capacitor and voltage, 10%~20% transducer about renewable power system rated torque. If a choice of brake unit, can reach 50%~100%.
18, please indicate the protection function of frequency converter?
Protection functions can be divided into the following two categories:
(1) detecting abnormal state automatically correcting action, such as the current stall prevention, renewable overpotential stall prevention.
(2) detecting abnormal after blockade of power semiconductor devices in PWM control signal, the motor automatically stop. As a current cut, cut renewable overpotential, and instantaneous power semiconductor cooling fans overheating protection.
19, why use the clutch is connected with the load, the protection function of frequency converter on the action?
Clutch is connected with the load, in the instant connectivity, motor from the no-load state to slip large regional drastic changes, a large current flows through the resulting converter overcurrent trip, not run.
With 20, large motors in the same factory, functioning transducer on the end, is this why?
The motor will start flowing and capacity relative to the starting current, the electrical stator side of the transformers have a voltage drop, the motor capacity when the drop impact is large, the inverter is connected on the same transformer will make qianya or correct judgement stopped, and thus sometimes protection functions (IPE) movements, causing cessation of operation. 21, what is the frequency resolution? What's the point?
For digital control of the transducer, even if the instructions for the frequency analog signal, the output frequency is a class given. The reason for the smallest unit known as the frequency resolution. Frequency conversion resolution typically value of 0.015~0.5Hz. for example, the resolution is 0.5Hz, then the above variable 23.5 for 23Hz, 24 Hz, therefore there is a level of electrical movements follow. Such as continuous roll uses control by the problem. In this case, if the resolution is about 0.015Hz, for the 4 stage motor 1 levels below 1r/min, can fully meet. In addition, some types of aircraft to the resolution and the output resolution is not the same.
22, set the installation directions are restricted transducer.
Transducer internal and back into the structure of the cooling effect, on the relationship of ventilation is important, therefore, in order for the type of unit, hanging on the wall to the vertical position, the installation of vertical as possible.
23, do not use soft start, whether the motor can be directly into a fixed frequency transducer?
At low frequencies, can, but if given the frequency with the frequency of high-power direct starting with similar conditions. Will flow through the large starting current (6~7 times rated current), as a current transducer cut, the motor can not start.
24, the motor exceeds 60Hz operation should pay attention to what the problem?
More than 60Hz operation should pay attention to the following matters:
(1) machinery and equipment in the speed of operation to be fully possible (mechanical strength, noise, vibration, etc.).
(2) motor is in the range of constant power output, the output torque to be able to maintain the work (output power of fan, pump shaft in proportional to the cube of speed increase, so the speed a little higher also want to notice).
(3) have the life expectancy of bearings, to be fully considered.
(4) for more electrical capacity, especially the 2 pole motor, running in more than 60Hz with manufacturers to discuss carefully.
25, the converter can drive gear motor?
According to the structure and lubricating mode reducer is different, need to pay attention to some problems. In the gear structure is usually considered as the maximum limit of 70~80Hz, using oil lubrication, to gear damage under continuous operation at low speed.
26, the inverter can be used to drive single-phase motor? You can use the single-phase power supply?
Basically can not use. The governor switch starting of single-phase motor, the working point below the speed range will be burned auxiliary winding; capacitance or capacitance to start operation mode, will trigger capacitor explosion. Transducer 3 of the power normally, but the capacity for small, single-phase power is also useful functioning aircraft.
How much power is 27, the transducer itself consumption?
Transducer with the aircraft, operating status, use of the frequency, but very difficult to answer. But in the converter efficiency approximately 60Hz 94%~96%, which can be estimated loss, but the built-in regenerative braking type (FR-K) transducer, if the loss is taken into account when braking, power consumption will become large, the operation of plate design must pay attention.
28, why can't 6~60Hz region-wide continuous operation?
Blade fan or the rotor end ring general electrical equipment used in the shaft on the cooling, if the lower speed cooling down effect, and thus can not afford high-speed operation with the same heat, to reduce the load of low-speed torque, or a large capacity inverter and motor combination, or the use of special motor. 29, the use of motor with brake, should pay attention to what?
Brakes exciter circuit power should be taken from the input side converter. If the transducer is output power brake action, will cause a current cut. So to make the brake action in the inverter output after the stop.
The 30, want to use converter drive motor capacitor with improved power factor, the motor is not moving, please explain why.
Capacitor transducer into the current improvement in the power factor, due to the charging current caused by current transducer (OCT), so we can not start, as a countermeasure, please the capacitor will be removed after operation, and improve the power factor at the input side converter, the access of AC reactor is effective.
31, inverter life how long?
Transducer is for static devices, but also as filter capacitor, a cooling fan that consumption device, if they carry out regular maintenance, is expected to have more than 10 years of life.
32, a transducer containing cooling fan, wind direction? If the fans will be bad?
There are no cooling fan models for small capacity. There are fans of aircraft, the wind direction is from bottom to top, so the installation transducer place, upper part and lower part, do not place hinder the suction, exhaust mechanical equipment. Also, do not place the transducer above heat parts etc.. Fan malfunction, the fans stop detection or cooling fan overheat detection protection
33, filter capacitor for consumables, how to judge its life?
Capacitor used as a filter capacitor, the electrostatic capacity over time and slowly decreased, regular measurement of capacitance, to judge life to meet product of the rated capacity of 85% for the benchmark.
34, set the installation directions are restricted transducer.
Collections in order to be fundamental, the problem is the fully enclosed disc size structure, occupying a large space, the cost is relatively high. It measures:
(1) the practical devices designed to address the needs of heat;
(2) using aluminum fins, vane coolant increased cooling area;
(3) using heat pipe.
What is the 35, inverter DC reactor role?
To reduce the input current harmonics, improve the power factor of the input power.
36, annex sine inverter filter what effect is there?
Motor cable running sine filter allows the converter using long, also apply to the intermediate transformer between inverter and motor loop.
Resistance given potentiometer 37, inverter value how much?
Given potentiometer transducer resistance is generally 1K to 10K.
38, why the converter cannot be used as a variable frequency power supply?
Variable frequency power supply of the circuit is composed of a communication exchange has been a filtering part, so its output voltage and current waveforms are pure sine wave, the AC power supply is very close to the ideal. Can any country in the world to voltage and frequency output. The inverter is composed of alternating flow has an AC (modulation) circuit, inverter standard name should be the frequency governor. The waveform of the output voltage pulse square wave, and the harmonic, voltage and frequency at the same time proportional change, can not be adjusted respectively, do not meet the requirements of the AC power supply. In principle, do not use the power supply, generally only used for the speed control of three-phase asynchronous motor.
39, inverter which disturbances and how to deal with?
Mode of transmission:
(1) radiation interference;
(2) conducted interference
Anti-interference measures: for by radiation propagating stem | | | author: Published at: 2013/4/28 15:31:29 |  |
|
|
