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Working safely with compressed air  tank

Working safely with compressed air tank

Safely using of compressed air tank is a very important issue, compressed air tank before being used must be tested by KTAT, registered for use following regulations. Users must hand over the managing responsibility the compressed air tank to the equipment manager in writing. Operating of thetanks is only given to people from 18 years old or older, who are physically fit and well-trained. They must be assigned by the employer in writing.
Supply Hanshin NXL-3000 oil compressor

Supply Hanshin NXL-3000 oil compressor

Minh Phu Machinery and Technical Services Co., Ltd specializes in providing repair and maintenance services and parts: Oil, Separator, Oil Filter, Air Filter ... for Hanshin compressors.
Piston air compressor repair

Piston air compressor repair

Minh Phu Machine and Technical Services Co., Ltd specializes in repairing, maintaining and supplying Piston air compressor parts: air compressor oil, air filter, oil cap, cement ... . Please contact us (Mobile: 0919 23 28 26 - Email: phu82bg@gmail.com) for professional services and competitive price.

Maintenence chedule of desicant air dryer (heatless type)

Compressed air system in factory plays an important role. In order to ensure the stable operation during the manufacturing process, the regulary maintenance is nescessary . However, there are many different problems in fact such as: Air compressors, dusty air dryers, high engine room temperatures, unsecured wind convection ... lead to reduce using time of compressor accessories (air filter, oil filter, oil separator ...). On the other hand, the recommended maintenance in some factories is not seriously followed and there are deviations. To extend the life of the machine as well as compressor components and ensure operator safety Air compressors are very important to maintain regularly and technically correct.Air compressors, dusty air dryers, high engine room temperatures, unsecured wind convection ... lead to reduced use time of compressor accessories (air filter, loc oil, oil separator ...). On the other hand, the maintenance (maintenance) recommended by the manufacturer in some factories is not guaranteed and there are deviated. To lengthen longevity of mạchine as well as compressor components and ensure operator safety , air compressors are very important to maintain regularly and technically .

Electric wiring and Power Facilities of GRH3 air compressor

Electric wiring and Power Facilities of GRH3 air compressor

Speed control methods of the asynchronous motor

Wednesday - 02/01/2019 03:42

How to adjust motor speed? How many methods to adjust  motor speed ?

How to adjust motor speed? How many methods to adjust  motor speed ? Many problems have been studied about adjusting  asynchronous motor speed, but generally, there is advantages and disadvantages in  asynchronous motor speed adjustment methods  and can not   solve all problems such as adjustment scope, power consumption, flatness in adjustment and devices 
The main methods can be used:
 - On stator: change the voltage suppling  stator , change the pole number of stator or change the source frequency.
 - On the rotor: change the rotor resistor or connect serially on the rotor circuit one or many connectors.

 

sua motor may nen khi

1. Adjust the speed by changing the number of pole pairs
The speed levels correspond to the number of polar pairs that the stator winding can be connected. Therefore, the speed can only be changed unevenly one by one. There are many ways to change the number of poles of the stator winding
- Change the wiring to have a different number of pole pairs. Used in two-speed electric motors in a 2: 1 ratio
- On the stator groove, place 2 independent windings with different number of pole pairs, usually to achieve 2 speeds in a 4: 3 or 6: 5 ratio
- On the stator groove, there are 2 independent windings with different number of pole pairs, the connection of each winding can be changed to have different number of poles.
The rotor winding in a winding asynchronous rotor has the number of pole pairs equal to the number of poles of the stator winding. Hencen, when reconnecting the stator winding to have different number of poles, the rotor winding must also be re-matched, which is inconvenient
In contrast, the squirrel cage rotor winding adapts to any single pole length of the stator winding, thus, it is suitable for electric motors to change the number of poles to adjust the speed.
Although the speed adjustment level is unstable, it helps to keep the stiffness of the mechanical properties.
2. Adjust the pitch by varying the frequency
Speed ​​of motor KĐB n = n1 (1-s) = (60f / p) (1-s)
When the slip coefficient changes little, the speed is proportional to the frequency.
On the other hand, from the expression E1 = 4.44f1W1KdqØmax we find that max is proportional to E1 / f1.
It is desirable to keep Ømax = const
E / f is adjusted for this purpose at the same time, which means it is required to use a special power source which is the industrial frequency converters.
Due to the strong development of microelectronics and power electronics, the inverters has opened up a great prospect in the field of controlling AC motors by frequency method. Using inverters to control the motor according to different rules (U / f rule, vector control ..) has created a motor speed control system with outstanding features.
3. Adjust the speed by varying the stator supply voltage.
It is known that the limit slip coefficient Sth does not depend on voltage. If R’2 is constant, when reducing the source voltage U, the limit slip coefficient Sth will no longer decrease Mmax proportional to U2.
 This method is only implemented when the machine is loaded. When the machine is not unloaded, and the power supply is reduced, the speed remains roughly stable.
4. Adjust the speed by changing the rotor circuit resistance of the winding rotor motor.
Through the slip ring, an adjustable 3-phase resistor is connected to the rotor winding
For a given load torque, the larger the auxiliary resistance, the greater the slip at the operating point (from a to b then c) leading to the lower the speed. Since the torque is proportional to the resistance power Pdt, we have: (r2 / s2) = ((r2 + rf) / s)
Since Pdt itself is constant, I2 is also constant so a part of the former mechanical power has turned into loss I2 x Rf. Since the input capacity is constant at that time, the efficiency is reduced, This is the disadvantage of this method. On the other hand, whether the speed of adjustment is more or less depends on the large or small load.

 

Methods of adjusting the speed of asynchronous motors, wrapping air compressor motors, repairing air compressor motors,

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