One, what's a frequency transformer
The frequency transformer is an electrical power control device that converts the industrial frequency power to a different frequency using the break-up of the power semiconductor device. It achieves such functions as soft start, variable frequency modulation, increased operational accuracy, power change factor, overflow/pressure/overload protection for the exchange accelerator。
Different points between 2, pwm and pam
The pwm is an abbreviation of the english pulse width modulation (pulse width) that changes the pulse width of the pulse column in a regular manner to adjust the output and wave shape. Pam is the english pulse implitude modulation (pulse band) abbreviation, which is a mode of adjusting output values and wave shapes by regularly changing the pulse range of the pulse column。
3. Why is the voltage and frequency ratio of the variable
Any electron-monetized magnetic rectangular is the result of the interaction of currents and magnets, which are not allowed to exceed their rated values, otherwise they will cause thermal heat of the motors. Therefore, if magnetic flux is reduced, the electromagnetic rectangular is reduced, resulting in lower carrying capacity。
As can be seen from formula e = 4. 44*k*f*n***, at the rate of variable frequency modulation, the magnetic circuit of the electric motor changes in a considerable range with the frequency fx, which makes it extremely easy to saturate the magnetic circuit of the electric motor, leading to serious waveform malformations of the magnetic current, producing high peak currents。
Therefore, frequency and voltage are to be changed proportionally, i. E. The frequency is to be changed while controlling the output voltage of the variable, so that the magnetic flux of the motor is maintained to avoid weak magnetic and magnetic saturation. This control is used mostly in wind machines, pump-type energy-efficient variants。
4. When v and f are proportionately modified, how does the switch of the electric power change
When the frequency drops, the voltage is reduced in full proportion, so that direct current resistance remains constant because communication resists transformation, creating a tendency to reduce the rectangles at low speed. Therefore, v/f is given at low frequency to increase the output voltage in order to obtain a certain start-up rectangular, which is referred to as enhanced start-up. It can be achieved using various methods, such as automatic processes, the choice of v/f models or the adjustment of the electrical level。
5 in the instructions, it is written that the speed range 60-6 hz, or 10:1, does not have output power below 6 hz
The output power is still available below 6hz, but the minimum frequency of use is around 6hz depending on the temperature of the electric machine and the size of the starter rectangular, at which point the electric motor can export the rated rectangular without causing serious heat problems. The actual output frequency (starter frequency) of the variable is 0. 5-3hz based on the type of machine。
What do you mean, "opening"
The speed checker (pg) is placed on the electrical device in use, and the actual velocity feedback is given to the control device, called "closed ring", or "opening" if it does not operate. The general-frequency variants are mostly open-ringed, and some of the machines use an option to provide pg feedback.... The no-velocity sensor closed-ring control is based on the actual speed of the magnetic-guided generator based on the established mathematical model, which is equivalent to a virtual speed sensor forming a closed-ring control。
7. What happens when there is a deviation in the actual rate of rotation from the given rate
At the time of opening, even when the frequency is exported to the given frequency, the rate of transmission of the electrical power varies between 1 and 5 per cent of the rated rate when the electric power is mounted on a load. For high speed-resort accuracy, even load changes require the use of a pg feedback variable (optional) at a time close to the given speed。
8. Would the speed accuracy of feedback be improved if it were used with a pg
A pg feedback variable with increased precision. However, the value of the speed accuracy depends on the precision of the pg itself and the resolution of the frequency of the output of the variable。
What do you mean
If the acceleration time given is too short, the output frequency of the mutator is much more variable than the rate of rotation (angular frequency), the mutator will jump through the current and be shut down, which is called a failure. In order to prevent the failure of speed to keep the power going, frequency control is to be performed by checking the size of the current. When the acceleration is excessive, the acceleration rate is appropriately slowed. The same is true for slowing down. The combination of the two is the failure function。
What is the point of having an acceleration and a deceleration time for the type of machine that can be given separately and for which the reduction time is shared
The additional speed reduction may be given separately, and is appropriate for short-term acceleration, slow deceleration, or when small machine beds require strict timing of production nodes, but for winding, etc., the additional speed reduction is longer and the acceleration and reduction time can be given together。
What are the protections in all of them
The protective function can be divided into two categories:
(1) automatic corrective actions after detection of abnormal conditions, such as prevention of run-off and prevention of regenerative voltage failure。
(2) the electrical semiconductor device, pwm control signal, is blocked after detection of anomalies, and the electric machine automatically stops. For example, electrical current cut-off, regenerative voltage cut-off, semiconductor cooling fan overheat and instantaneous power outage protection。
12. Why does the protection function of the variable act when it connects the load with a clutch
When you connect loads with a clutch, in the instant of the connection, the electric generator changes dramatically from an empty state to an area with a high rate of deviation, and the large current that passes through the current jumper is rendered inoperable。
13, the same plant, where the large electric power sets work together, the active transducer stops. Why is that
When the power is activated, the flowing and capacity corresponding to the start-up power, the transformer on the fixed side of the generator produces a voltage reduction, and the effect of this reduction is greater when the power capacity is large. The transformer connected to the same transformer will make an under-pressure or instantaneous judgement, thus sometimes protecting function (ipe) actions, resulting in the suspension of operations。
14. Is it possible, without soft start, to direct the electric power into a fixed frequency variable
It is possible at a low frequency, but if the frequency is given at a high rate, the conditions are similar to those for direct start-up of the working frequency power source. Excessive start-up currents (6-7 times rated), which cannot be activated as a result of the cut-off of the frequency。
15, can a frequency transformer drive a single camera? Can we use single-phase power
It's basically not working. Auxiliary circuit groups will be burned when the speed range below the work point is applied to single-phase motor switches and, in the case of capacitation or the mode of operation of the capacitor, the generator container will be induced to explode. The power source of the frequency transformer is usually 3-phase, but for small capacity, a single-phase power source is also used。
16. If you want to use a frequency transformer to move a power-improvement factor with a capacitor, the electric power is not moving, please explain why
The current flow of the transformer into the capacitors used for the power improvement factor cannot be activated because it is charged to cause the current to pass (oct). In response, please remove the capacitors and operate with the improved power factor, it is effective to access the ac resistance on the input side of the transformer。
17, there's a cooling fan in the transmission. How's the wind? What happens if the fan breaks
There are also non-cooled fans for small capacity. The type of device with a fan, the direction of the wind is from the bottom up, so where the frequency is installed, no mechanical devices that obstruct inhaling and exhausting air are placed up and down. Also, no heat-resisting parts above the frequency transformer. When a fan fails, it is protected by either suspension or overheating on cooling fans。
18, what's the use of the frequency attachment sine filter
Sine filters allow the frequencyrs to operate with longer electric cables and also apply to circuits with intermediate transformers between the frequencyrs and the generators。
19 - why can't a frequency transformer be used as a power source
The entire circuit line of the variable-frequency power source has been part of a current-to-penetration filter, so its output of both the voltage and the current wave shape are pure sine waves that are very close to the ideal exchange power source. It can export grid voltage and frequencies in any country in the world. In contrast, the variable is made up of circuits such as communication and constant flow communication (modulation waves), and the standard call for the variable frequency moder. The wave shape of the output voltage is a pulsed spectrometer, with a large harmonization composition, with a proportional change in the voltage and frequency, which cannot be adjusted separately and does not meet the requirements of the power exchange. In principle, the power supply cannot be used, usually only for the speed of the three different pacers。
20. What are the ways in which the variants are disturbed and how are they dealt with in general
Mode of dissemination:
(1) radiation interference
(2) transmissive interference
Anti-disruption measures: disruptive signals transmitted by radiation are weakened mainly by wiring and by shielding radioactive sources and disturbed lines. Interference signals transmitted by circuit are handled primarily through the installation of filters on the side of the output input of the mutator, electrical resistors or magnetic rings. Specific approaches and attention are as follows:
(1) the signal line and the power line shall be vertically cross or subtwinned。
(2) do not use guidance lines from different metals to connect。
(3) the shielding tube (layer) shall be reliably connected to the ground and shall ensure continuous and reliable access throughout its length。
(4) two winch shield cables shall be used in signal circuits。
(5) the shielding site is as far away from the frequency adapter as possible and separate from the frequency adapter site。
(6) magnetic rings may be used in the input of electrical power lines and output lines by the same four-rounding of the input line in the same direction and three-rounding of the output line in the same direction. Be careful when bypassing, and as close as possible to the frequency transformer。
(7) in general, shielding and other anti-interference measures may be applied to the equipment or instruments that are disturbed。
