Frequency conversion motor 33 Q
1, what is the frequency converter?
Converter is the use of power semiconductor devices will be the role of off frequency power conversion to another frequency power control device.
2, the voltage type and current type inverter have what different?
The main circuit of inverter can be divided into two categories: voltage is DC transformvoltage source for AC inverter, DC loop filter is capacitance; current model is the DC converter current source to exchange converter, the DC loop filter is the inductance.
What is the difference of 3, PWM and PAM?
PWM is English Pulse Width Modulation (pulse width modulation) abbreviation,according to certain rules to change the pulse trains of the pulse width modulation, in a regulated output and waveform.
PAM is the English Pulse Amplitude Modulation (pulse amplitude modulation)abbreviation, is according to certain rules to change the pulse train pulse amplitudemodulation to a regulated output value and waveform.
4, the use of the frequency power driven motor, voltage drop, current increases; forinverter drive, if the frequency voltage drop, then the current is increased?
Decrease of frequency (low speed), if the same power output, the current increase intorque, but under certain conditions, current is almost invariant.
5, why the inverter voltage and current proportional to the change?
The torque of the motor is between the current flowing through the motor flux and rotor interaction in and produce, at rated frequency, but only if the voltage will reduce the frequency, then the magnetic flux on a large, magnetic circuit saturation, serious when will burn motor. Therefore, the frequency and voltage in proportion to thechange, at the same time control inverter output voltage change frequency, so thatthe motor flux is maintained, avoiding the weak magnetic field and magnetic saturation phenomenon. This means more control for fan and pump energy saving converter.
6, the V/f mode is what mean?
Frequency voltage drop V is proportional decline, in answering this question has 4 description. The ratio of V and f between the electrical characteristics and is considered a predetermined, usually in a storage device controller (ROM) has several characteristics, can use the switch or dial to select
7, using frequency converter operation, motor starting current and starting torque?
Using frequency converter operation, along with the acceleration of motorcorresponding to improve the frequency and voltage, the starting current is limited to 150% below the rated current (according to different models, 125%~200%). Starting directly with the power supply, the starting current is 6~7 times, therefore, will produce mechanical electrical shocks. 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; for with automatic torque enhancement function of the inverter, the starting torque is above 100%, can take a full load starting.
8, 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 of the size and other conditions, the minimum frequency for about 6Hz, the motor can output the rated torque and the heat will not cause serious problems. The actual output frequency converter (starting frequency) according to themodels of 0.5~3Hz.
9, according to the proportion of modified by V and F, the torque changes in the electrical?
Frequency fully reduced in proportion to the voltage, so the AC impedance smaller and DC resistance unchanged, will result in low speed generated torque is reduced tendency. Therefore, when given in low frequency V/f, to make the output voltage is improved, in order to obtain a starting torque, such as enhanced compensation package. Can be achieved using various methods, a method, automatically select the V/f mode or adjust potentiometer method
10, the portfolio is in the general electrical 60Hz above also requires a certain torque,can?
Can not normally when. In the above 60Hz (a 50Hz above model) voltage unchanged,is substantially constant power characteristic, require the same torque at high speed,must pay attention to the choice of motor and inverter capacity.
11, if the motor with PG, after feedback to improve the accuracy rate?
Frequency converter with PG feedback function, precision was improved. But the speed depends on the accuracy of the PG itself and precision of the inverter output frequency resolution.
The 12, 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.
13, the actual rotational speed for a given speed deviation when how to do?
Open loop, inverter output even given frequency, motor operation in a load, the range of the motor speed slip in the rated (1%~5%) changes in the. For the requirements of speed accuracy is relatively high, even if the load changes also required to operate inclose to the given speed occasions, can function with PG feedback transducer(optional).
14, stall prevent functional is what mean?
If given a short time to accelerate, transducer frequency changes far exceeds the output speed (electric angular frequency) changes, the frequency converter will be a flow of electric current and Tiaozha, stop functioning, which is called stall. To prevent stall continued operation of motors, frequency control to the size of the currentdetection. When excessive speed up current accelerated rate due to slow. So is thedeceleration. The combination of the two is the stall function.
15, what is the regenerative braking?
The motor in operation if reducing instruction frequency, the motor into asynchronousgenerator running state, while working as a brake, which is called regeneration(Electrical) brake.
16, whether can get larger braking force?
Regenerated from the motor energy storage in the filter capacitor inverter, due to the relationship between the capacity of the capacitor and voltage, 10%~20% transducer about renewable power system rated torque. Such as the use of optional braking unit,can reach 50%~100%.
17, the acceleration time and deceleration time machine can respectively given, andacceleration and deceleration time jointly given models, what's the point?
Slowdown were to be added to the aircraft for a short time to accelerate and slow deceleration is suitable for occasions, or for small machine tools needed to set strictproduction time of the occasion, but for the fan drive and so on, the slowdown has had a longer time, the acceleration time and deceleration time can be common.
18, why use a clutch of continuous load, protect the function of frequency converteron the action?
Clutch is connected with the load, in the instant connectivity, motor is transferred from the empty state to guide large regional drastic changes, a large electric current to flowconverter overcurrent trip, can run.
19, what is the frequency resolution? What's the point?
For the inverter digital control, even if the instructions for the frequency analog signal,the output frequency is a class given. The reason for the smallest unit called thefrequency resolution.
Frequency resolution typically value of 0.015~0.5Hz. for example, the resolution is 0.5Hz, then the above variable 23Hz to 23.5 and 24 Hz, so there is a level of electrical movements follow. Such as use for continuous roll to take control will cause problems.In this case, if the resolution is about 0.015Hz for the 1 graduation class 4 motor is below 1r/min, can fully adapt to. In addition, some types of aircraft to the resolutionand the output resolution is not the same.
20, large motor move together in the same factory, functioning transducer on the end,this is why?
The motor will start flowing and capacity relative to the starting current, motor statorside of the transformers have a voltage drop, the motor capacity at the big impact is large Yajiang, inverters are connected in the same transformer will make qianya or correct judgement stopped, and thus sometimes protection function (IPE) caused byaction, stop running.
21, do not use soft start, whether the motor can be directly into a fixed frequency transducer?
At very low frequencies can be, but if given the frequency with the frequency of high-power direct start 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.
22, the converter can drive gear motor?
According to the structure and lubricating mode of speed reducer is different, need to pay attention to some problems. In the gear structure is usually the biggest limit to be considered 70~80Hz, using oil lubrication, under continuous operation at low speed togear damage.
23, installation of frequency converter installation directions are limited?
Structure of frequency converter internal and back to consider 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.
24, the motor exceeds the 60Hz operation should pay attention to what the problem?More than 60Hz operation should pay attention to the following matters:
(1) mechanical and running to in the speed of fully possible (mechanical strength,noise, vibration etc.).
(2) motor is in the range of constant power output, the output torque to maintain work(fan, pump shaft power output in proportional to the cube of speed increase, so thespeed 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, operating in more than 60Hz with manufacturers to discuss carefully.
How much power consumption 25, the inverter itself?
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 cancalculate the loss, but the built-in regenerative braking type (FR-K) inverter, if the loss of braking is also taken into consideration, power consumption will become large, theattention must be paid to operation panel design.
26, the frequency converter can be used to drive single-phase motor? You can use the single-phase power supply?
Basically can not be used. The governor switch starting of single-phase motor speed control, in the scope of work is the auxiliary winding will be burned; 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.
27, why not in the 6~60Hz region of continuous operation?
Outer 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, the need to reduce the load of low-speed torque,or a large capacity inverter and motor group, or with special motor.
28, the use of motor with brake, should pay attention to what?
Brake excitation loop power supply should be taken from the inverter input side. If the transducer is when the output power of brake action, will result in a current cut off. Sothen the brakes in transducer moves to stop output.
29, inverter life how long?
Transducer is for static devices, but also that consumption device like a filter capacitor and a cooling fan, if they carry out regular maintenance, is expected to have 10 more years of life.
The 30, want to use converter drive motor capacitor with improved power factor, the motor is not moving, please explain why
The current flowing into the capacitor inverter power factor improvement used, due to the charging current caused by current transducer (OCT), so we can not start as a countermeasure, please capacitor removed after operation, and even improve the power factor at the input side converter access AC reactor is effective.
31, a transducer containing cooling fan, wind direction? If the fans will be bad?
There are no cooling fan model for small capacity. There are fans of aircraft, the wind direction is from bottom to top, the installation transducer place, mechanicalequipment and placed an image not suction, exhaust. Also, do not place the heatconverter above parts etc.. Fan failure, by fan stop detection or on the cooling fanoverheat detection protection.
32, to improve the speed of the conveyor belt in the original, 80Hz operation, the capacity of the transducer how to choose?
Set the reference speed for 50Hz, 50Hz or more for the characteristics of constant power output. Like a conveyor belt constant torque characteristics of such loadgrowth, capacity needs to be enlarged for 80/50 is about 1.6 times. Increasing the motor capacity also as transducer.
33, installation of frequency converter installation is restricted location?
Collections in order to be fundamental, the problem is with a fully enclosed discdimension of structure is big, the occupied space is large, the cost is relatively high.The measures are:
(1) disc design to need according to the actual device heat dissipation;
(2) the use of aluminum heat sink fins, coolants, increase the cooling area;
(3) using heat pipe.
In addition, has developed a transducer back can be exposed type.
