Many electricians, workshop crews have daily contact with the frequency transformers, which are wired, deactivated and adjusted, but never understand what really changes the frequency transformers. Most people know only vaguely that it can switch the power machine slowly, but they don’t know that a change in the frequency will burn the power machine, and they don’t know how the 50-hz fixed power will turn into a zero-400-hz transferable power source; others see the speed, energy-efficient, soft start as an independent function, without seeing the uniform electrical logic behind it。
This paper leaves aside the complex formula of high numbers, with two core changes to break down the frequency of the frequency of the output exchange, synchronized changes in the output voltage, complete description of the clean-up- straight-turning process, v/f constant bottom logic, five practical changes resulting from the variable frequency, distinguishing between winder pumps, conveyance bands, machine beds, combining the high-frequency perception error areas of the first-line electrician, supported by full-scale case studies, and zero basic apprentices, who also have access to the principles and are no longer experienced blind。
First, to start with the bottom root: the grid is fixed and the rate of transmission is determined only by frequency
The low-voltage grid of domestic plants produces three-stage 380 v, 50 hz exchanges of electricity, which are fixed and cannot be directly regulated. There's a core formula for the communication walker: synchronous = 60f/p。
Formula disassembly: 60 is a minute conversion factor, p is an electron polar logarithm (the plant is fixed) and f is a power frequency。
To illustrate intuitively: 4 poles p = 2, access to 50 hz industrial frequency, synchronous velocity 1,500, access to 25 hz power, direct velocity to 750。
Conclusion: the number of electrons can't be changed, and the only viable path to a free velocity is to change the frequency of the electricity, which is the very purpose of the birth of the frequency。
A key question arises here: only change the frequency, not the voltage, and the power must be overheated。
Assuming a direct reduction of 50 hz to 25 hz, the voltage remains at 380 v, the internal magnetism of the electric machine will be doubled to saturated, the iron core vortex and the copper loss of the wire will surge and there will be a crumb and a short interlude for 10 minutes. The electron circuits react positively to electric motion and voltage, frequency, and in order to stabilize the magnetic flux in the safe zone, the u/f = constant (pressure frequency-consistent) must be followed, and the reduction of the frequency must be accompanied by a reduction of the voltage at a rate equal to that of a higher frequency up to a maximum of 380 v。
One sentence summing up the core of the frequency transformer: it changes two things at the same time — the frequency of the transmission, the power output voltage, which is adjusted to be safe and smooth in controlling the speed of the transmission and the twist。
Ii. Frequency changers complete electrical transformation in three steps and read the whole process of "change"
All market-based low-voltage transformers use the t-r-t structure, with three phases of streaming, straight-flow filtering and reverse transformation, each of which is being modified to complete the decomposition of the fm output。
Step 1: whole current (exchange of direct currents, first conversion)
The grid enters a fixed 380v/50hz exchange power, which is used through an internal two-pole integrated bridge to convert all the positive-and-neutron exchange power into a single-direction pulsation direct current, which is approximately 540 v after the 380v whole flow。
This step involves stripping off the grid of fixed frequencies, limits on fixed voltage, and transforming electricity into a stable straight current “energy pool”, followed by a free-flowing space。
Similarity: the whole flow chain is equivalent to the tide of rising and falling rivers, all pouring into fixed reservoirs and no change in the direction of the current。
Step 2: straight-flow filter wave pressure (intermediate buffer)
The current flow is a high- and low-volatile pulsation that cannot be directly driven by a high volume electrolytic conceiving, direct current resistance flat pressure, and receives a flat straight-flow parent voltage。
Capacitation also carries the role of a reservoir: it absorbs the feedback when power is generated at reduced speed, it releases the power at the moment of its heavy load, it avoids sharp voltage fluctuations and it guarantees the stabilization of the reverse chain。
Step three: reverse change ( straight current power mod-fm communication, core transformation)
This is the key link in the real "variable frequency transformer" of the variable, which uses igbt high-speed power switches to cut direct current electricity using spwm sine-wire techniques:
1. Changes in the speed of the igbt cut-off switch, which can change the frequency of the output exchange, with a range of 0. 1 to 400 hz to be continuously adjusted
Change the width (space ratio) of the pulses of each group, and the equivalent changes the output exchange power (ec) efficiency to achieve synchronous voltage
3. Numerous narrow, cyclical pulse superstitions, i. E. Simulations of flat-string three-phase power supply machines。
Simple analogue reverse processes: water in reservoirs, through high-speed valves, control valves open quickly (frequency), how much water is discharged once (voltage), flowing out of water as needed, perfect match to the electrical operation requirements。
Iii. Two core changes to the frequency transformer: frequency, transformer, and split-down
(i) change of output frequency: direct control of electrical retrofit, no step velocity
1. Low frequency band (0~50hz, within base frequency)
The lower the frequency, the slower the motor turns, while simultaneously lowering the output voltage, maintaining a constant magnetic passivity and a constant twist of the output. The conveyor belts, mixers and cranes are all working in this zone, and are capable of producing enough pull at a low speed to enable them to slide。
In the case of exercise: the transmission line is running at an empty 20-hz speed of 600 rotations; the full-load production of 40-hz is running at a speed of 1,200 turns, the full-twirling is sufficient without the need for additional speed-cutting units。
2. High frequency segment (above 50 hz, outside base frequency)
The grid's rated voltage is only 380 v, the voltage cannot continue to rise, the magnetic flux drops when the frequency is raised and the electron twists down at the same time, which is a constant velocity. For high-speed grinding, wind engine speed scenes, a normal wind pump does not recommend a long-term over50 hz operation, and the twisting is not easy to overload。
Core advantages: whfs can operate at full speed only at 50 hz, relying on valves, barriers, clutches, mechanical retrofits, high losses and poor accuracy; variants 0-50 hz are continuously ungraded, speeds can be fine-tuned and process suitability significantly improved。
(ii) synchronization of output voltage: protection of electric power and maintenance of stable rectangulation
Many beginners focus only on the frequency, neglecting the need for synchronous voltage, in two cases indicating the logic of tuning:
1. Imperative pressure reduction (0~50hz)
The frequency is halved and the voltage synchronized is halved to ensure that the u/f margin remains unchanged and the magnetosphere is not saturated to avoid the high temperature of the coil burning. When 25hz is running, the output voltage of the variable is only around 190 v, matching the low-frequency magnetic field requirements。
2. Intensity no pressure (>50hz)
After a frequency exceeding 50 hz, the output voltage locking on the 380v rating no longer rises, the magnetic flux continues to decline and the twister is reduced, which is also the underlying cause of the weakness of the high-speed working conditions。
Complementing special control mode: vectors can provide a separate fine-tuned rate of compensation for voltage, low-speed lifting of a small amount of voltage, repairing the line pressure, and eliminating the low-speed twister, which in essence continues to be the logic associated with the fm。
Iv. Five visual changes in equipment will occur as a result of variable frequency transformer pressure
The frequency transformer changes only two electrical parameters, but extends out of the five most practical functions of the workshop and is the central reason for the large number of transformers installed in the plant。
Change 1: power-software start-up to eliminate high-speed start-up shock
The working frequency directly activates the current 5-7 times the rated current, striking the grid in an instant, causing the voltage to drop and jump, while the gears, belts and bearings bear a huge mechanical shock and are vulnerable to damage to the fittings。
(b) the frequency transformer is operating from 0hz, 0v slow-to-pressurized frequency, initiating current stabilization control at 1 ~1. 5 times the rated current, smoothing acceleration, no impact, extending the useful life of the electric power, moving parts, and the essential function of a large water pump, wind machine。
Change 2: wind engine pumps are significantly energy-efficient as required
Wind machines and pumps are a square rectangular load with a three-fold positive ratio of power to rate: the rate of rotation is reduced to 80 per cent and electricity consumption is only 51. 2 per cent。
Work frequency operations can only close valves, and the electric power remains fully powered and excess power is converted to heat loss; the frequency transformer reduces frequency, lowers speed, matches actual flow demand, reduces energy consumption from the root causes and generally saves 15% ~35% of energy after retrofitting the recycle water pump and the dedustor。
Change 3: start-up, speed-reducing curves freely adjusted, precision-adapted
The conveyor belts, filling lines, packaging machines cannot be quickly stopped, material can be dumped, products can be damaged; the frequency transformer can set up a s-type and speed-reducing curve, smoothing up and down, without adding additional buffer mechanical structures and reducing equipment failure rates。
Change 4: improved electrical protection, early warning of electrical failure
In real time, it monitors output voltage, currents, frequencies, overflows, overloads, missing profiles, overheats, ground failure and immediate stoppage of the alarm, which is more sensitive to the protection of industrial frequency thermal relays and avoids the burning of the power plant in advance。
Change 5: two-way smooth brakes without additional brake parts
When the power is reduced, it becomes a generator, the power is fed back to the current carrier, the transformer is equipped with a brake to absorb the regenerative power, and the speed reduction is smooth; the high-speed main axis and the lifting equipment can be precisely positioned, and the power plant can be shut down only by friction of the brakes, with high wear speed and error in positioning。
Five, three mainstream control models, which are essentially voltage-relationer mode, but with different logic
On the market, the frequency transformer v/f control, vector control, direct rectangular control, all of which rely on a change of frequency, voltage, and the variance only adjusts the accuracy:
1. Control of v/f markers (general winder water pumps)
The fixed pressure frequency is more synchronous than the modulus, operating in an open ring, with a simple structure and a low price, suitable for wind machines, pumps and ordinary delivery lines that require less precision for the twisting。
2. Vector control (machinebed, mixing, lifting equipment)
Dismantling electric currents into magnetic and rectangular weights is self-regulated, low-speed voltage is compensated for precision, and 0hz can also export large rectangles with high-load fluctuations。
3. Direct rectangular control (high-precision server alternative scenario)
Direct real-time adjustments of magnetic fluxes and twists, most dynamic response, high-speed start-up, precision processing equipment, and fm real-time closed loop correction。
Six, 90% of the electricians will step on the six major cognitive error zones
Error 1: the frequency is only changed and the voltage is still working
Totally wrong. The low frequency will cause magnetic saturation of the steel core, the electric power will burn at high temperatures for short periods of time; only the rising pressure will not rise, the twisting will be severely inadequate, the load will not be moved and the decompression frequency will have to be synchronized。
No, no, no, no
The low-frequency long-term operation of the dispersive fan is synchronized with a decrease in the rate of wind rotation, the electric power itself is dissipated and overloaded at a low rate of less than 20 hz over a long period of time. Even when the pressure is normal, the heat rises above the standard, requiring the installation of an independent radiator。
Error 3: the frequency adapter can only slow down and not pick up speed
Over 50 hz can operate at high speed, but the maximum voltage limit of 380 v cannot be increased, the twisting will continue to decline, light-loading equipment will be able to pick up speed at short notice, and heavy-loading equipment will not recommend long-term over 50 hz operation。
Mistake 4: wind engine pumps and frequency transformers must save electricity
The energy saving effect is evident only in the daily state of the work that requires constant throttle and frequent changes in the flow; the 24-hour full-speed water pumps, wind machines, and the installation of frequency transformers, with little energy savings, increase the loss of the variable itself。
Erection 5: work frequency 50hz and transmission 50hz at exactly the same speed
The work-frequency power plant has a slippage and loss, the frequency vector model compensates for the slippage, which is set at 50 hz, slightly higher than the work-frequency directs, and the high accuracy equipment requires manual correction of the emulation parameters。
Zone 6: rf output pure sine wave, no damage to power
The reverse output is a pwm pulse simulated swirl wave, which contains a high frequency humonic wave, and long-range wiring requires the installation of an output antigenerator and the avoidance of a conjunction into the insulation of the electrons。
Vii. Quite diversity diversity: computer between vs
Corresponding dimensions. Work frequency 380v/50hz direct-off power
Power supply parameters, voltage, frequency fixes, 0~380v, 0. 1~400hz continuous
Speeding method mechanical throttles, clutches, heavy wear, electrical ungraded velocity, match load as required
Activate current, 5-7 times, shock, 1-1. 5 times, smooth
Low-speed twister. Low-speed twister is seriously short of 0-50 hz rectangular output
Energy consumption, light loads of full power, waste of power, down-frequency speed, significantly lower power consumption
Protection capability. Simple overload protection for heat relays. Overflow, missing phase, overheat, multiple real-time protection overland
Viii. Flm selection, debugging of the functional elements around the core logic of the fm
1. Winder pumps light-loading equipment: the selection of a normal v/f control variable, with a focus on matching the flow range, with the optimum energy efficiency for the daily running frequency of 30 ~45 hz
2. Combination, lifting, heavy transport equipment: selection of vector-type varianters to ensure low-frequency large twisters and appropriate voltage compensation when operating at low speed
3. Long-range wiring (over 50 m): add an output antigenerator, suppress the pwm wave, and protect the insulation of the electrical circuits
4. Long-term low-speed operating equipment: the installation of an independent heat winder on the electric power to avoid low-frequency dispersing heat below temperature rises
5. The debugging priority is given to the rated voltage, rated frequency of the electric presses, the system automatically matches the standard pressure frequency ratio and does not modify the v/f curve at will。
Ix. Comprehensive summary
There are only two changes at the core of the variable: the frequency of the output exchange, the voltage of the output exchange, which are accompanied by a simultaneous adjustment。
Using the t-r-t-t-t-t-c-t, fixed-work frequency exchange (rf-x) currents are first converted into direct currents, followed by gm-fm swirling through the igbt reverses; frequency determines the speed of the electric motor, and the voltage ratio is used to maintain magnetic stability of the iron core to prevent overheating and insufficiency of the electrics。
Based on the bottom capacity of the voltage fm, five functional functions are derived, such as soft start, no grader, energy efficiency, precision and speed reduction, multiple electrical protection, and extensive adaptation to industrial equipment such as wind dispensers, pumps, conveyance belts, machine beds, etc. The full advantage of the frequency transformers can be achieved by matching the control mode to the load type by avoiding fault areas such as the only modulation frequency that ignores the voltage, blind long-term low frequency/high frequency (lf/hf) operation and the perception that all equipment is becoming less frequent。
A simple sentence remembers the core: the frequency transformer is not a simple "modulator" but an electrical conversion device capable of simultaneously changing the voltage and frequency, and all functions are based on variable frequency transformers。
Have you ever tried to debug a frequency
What difference does it make between v/f or vector control
Have there been any cases of low-frequency operating electric heat spreads adding additional heat winders? The sharing of practical experience with electricians in the comment area is welcome。
