1 introduction
The air compressor has in the industrial production widely applies. It is shouldering for all air operated parts, including each kind of air operated valve, raises the air feed source the responsibility. Therefore it moves quality direct influence production craft. The air compressor type mainly has the plunger type, the screw rod type, but its air feed control mode nearly all is uses Canada, the unloading control mode.
2 electrical machinery principles and air compressor Canada, unloading air feed control mode existence electrical energy waste
2 (1) exchanges the asynchronous motor rotational speed formula is:
N=60f (1-s) /p
N - electrical machinery rotational speed f - movement electricity frequency;
P - electrical machinery 极对�?s - sliding;
2 (2) air compressor Canada, unloading air feed control mode existence question
2.1 energy consumption analyses
Canada, the unloading control mode causes the compression gas the pressure back and forth to change between Pmin ~ Pmax. Pmin is the minimal pressure strength value, namely can guarantee the user normal work the minimal pressure strength. In the ordinary circumstances, between Pmax, Pmin the relations may use the type to indicate that,
Pmax = (1 + delta) Pmin
Delta Is a percentage, its value approximately between 15% ~ 30%.

In Canadian, under the unloading air feed control mode air compressor, the energy which wastes mainly in 2 parts:
(1) increase when electrical energy consumption
After the pressure achieved the minimum value, the original control mode decided its pressure can continue to rise until the most tremendous pressure value. In pressurizes in the process, certainly must release more quantity of heats to the outside, thus causes the electrical energy loss. On the other hand, is higher than the pressure maximum value the gas in to enter in front of the air operated part, its pressure needs to pass through the pressure relief valve reduced pressure, this process similarly is consumes energy the process.
(2) unloads when electrical energy consumption
When the pressure achieved when pressure maximum value, the air compressor falls through the following method presses the unloading: Closes the admission valve to cause the electrical machinery to be at the idle operation condition, simultaneously will separate in the pot the unnecessary compressed air to blow off through the dump valve. This adjustment method must create the very big energy dissipation. According to us surveys, the air compressor unloads when the energy consumption approximately composes time the air compressor full load movement 10% ~ 25% (this or to occupy in proportion not big situation in disembarkation schedule). In other words, this air compressor 20% time are at the light condition, is making the useless merit. Very obviously in adds under the unloading air feed control mode, air compressor electrical machinery existence very big energy conservation space.
2.2 other deficiency
(1) depends on the mechanical way adjustment admission valve, causes to be unable for the spirit continuously to adjust, when unceasingly changes with the spirit, the air feed pressure inevitably has a larger scale undulation. With was mad the precision cannot achieve the technological requirement. In addition frequently adjusts the admission valve, can accelerate the admission valve attrition, the increase service quantity and the service cost.
(2) frequently uses turns on and closes the bleeder valve, the bleeder valve durability cannot obtain the safeguard.

3 constant pressures air feeds control plan design

In view of original air feed control mode existence many questions, but the application frequency conversion velocity modulation technology carries on the constant pressure air feed control. When uses this plan, we may the pipe network pressure take the controlled member, the pressure changes delivering YB to transform gas tank pressure P for the electrical signal gives the PID intelligence regulator, supposes definite value P0 with the pressure to do compares, and according to the PID control pattern which decides carries on the operation according to the difference value size, produces the control signal to deliver frequency conversion velometer VVVF, controls the electrical machinery through the frequency changer the operating frequency and the rotational speed, thus enable actual pressure P throughout to approach hypothesis pressure P0. At the same time, this plan may increase the processing frequency and the frequency conversion cuts the function, and retention original control and protection system, moreover, after uses this plan, the air compressor electrical machinery from static enough to revolved the work to be possible to start by the frequency changer, has realized the soft start, has avoided the start surge current and the start the machinery impact which brought to the air compressor.

4 systems primary devices select and match and the system installment and the debugging
4.1

System pressure request: Minimum pressure 6.2KG, most tremendous pressure 7.8KG.
Air compressor: 75KW 4 extremely electrical machinery screw rods type air compressor rotational speed 1470r/min,
Frequency changer: Taiwan Pu passes on pressure transmitter 1 (10KG)

4.2 systems installments and debugging
(1) installs
Controls the cabinet to install in the air pressure engine room, with originally controls the cabinet to separate, but matches the line with the compressor between host not to have to surpass 30m. The control loop matches the line to use the shielded twisted pair, the twisted pair line 节距 below 15m. Moreover on the control cabinet is loaded with the vent, frequency changer earth terminal certainly cannot mix with the power earth uses, above measure strengthened the system stability, the reliability.
(2) debugs
A) the frequency changer function hypothesis (different operating mode and control mode, function hypothesis are possible to be different)

The 01-00=1 hypothesis is 1: The movement instruction 端子 controls by exterior
01-05=20 rise time: The hypothesis is 20S, concrete value basis operating mode and production request
01-06=20 decelerates the time: The hypothesis is 20S
01- 10=50 biggest frequency: The hypothesis is 50Hz (is equal to electrical machinery nominal frequency)
01- 24=1 (supposes for standard electrical machinery)
01-25=100-105 electrical machinery over-load protection level: Concrete value basis operating mode and production request
05-00=1 PI control mode: Supposes for is effective
05-01=0 PI adjustment error polarity: Supposes for the positive electrode
05-02=0 PI demand signal choice: Supposes is 0
05-03=72% (assigns pressure value) the PI numeral given value (100% to correspond 10KG)
05-04=1 or 2 PI feedback signal choice
05-07=5-10 integration time 5-10 second
05-09=25 PI adjustment movement smallest frequency

(3) debugs the other businesses
Increases the processing frequency conversion installment, the entire wrap transformation installment certainly does not change the air compressor original control principle, original air compressor system protective device still valid. And the labor frequency/frequency conversion cut has used the electricity and the machinery dual interconnection, big enhancement system security, reliability.
In the debugging process, transfers to the lower limit frequency 40Hz, then with the infrared measured the warm meter ground-to-air press electrical machinery 温升 and the pipeline oil temperature has carried on the long time, the strict monitor, the electrical machinery 温升 approximately 2-4 �?between, is the normal 温升 scope, the oil temperature is basic 无变, the discharge temperature drops 5 �? Therefore the 40Hz lower limit frequency movement ground-to-air press unit's work is very safe.
(4) electricity saving data
After has not installed in front of the frequency conversion to use the electric quantity to install the frequency conversion every day to use the electric quantity every day
24 hours use electric quantity 17281417
Daily electricity saving 311
Electricity saving rate 18%

5 concluding remark
After a series of repeatedly adjustments, the final system stabilizes in the 39.5-42.5Hz frequency range, the pipeline pressure basically maintains at 0.69Mpa, the air feed quality obtains the enhancement. After the transformation the air compressor movement safe, is reliable, simultaneously had achieved the factory with the technological requirement which was mad.
Nanjing forever year industry limited company

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