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Electrical control technology and the latest development direction of centrifuge

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Electrical control technology and the latest development direction of centrifuge

Release date:2016-01-16 00:00 source: Click:

At present, some foreign advanced centrifuges have actually become a high-tech product technology. In this respect in our country there is a big gap, must enhance the technological content of the domestic production of centrifuge, efforts to develop products with independent intellectual property rights, in this respect there is a lot of work needs to be done. Centrifuge is a kind of electromechanical integration equipment has been widely used in the hospital laboratory, biology laboratory, biological pharmacy, sewage treatment, pharmaceutical and beverage production. It has penetrated into scientific research, production and other fields.

The selection of the drive motor

General motors used the DC motor and AC motor. The following characteristics of DC motor and AC motor.

1) DC motor characteristics. The complex structure, high cost, need regular maintenance (Replacement Brush), because there are sparks in the brush, generally not use explosion-proof occasions in requirements. But DC motor speed control circuit is simple, low cost, speed performance advantages, there is no brush DC motor performance has been mature, in the small power DC motor has been widely adopted brushless DC motor to replace DC motor.

2) AC variable frequency motor characteristics. Has the advantages of simple structure, low cost, reliable operation, low noise, in order to obtain excellent control performance, must adopt frequency conversion speed controller, complex, high cost. Because centrifuges can be configured with a variety of different speed rotor for drive centrifuge frequency conversion motor design should consider of rotor with low speed and large capacity, the motor work in constant torque region, the small capacity and high speed rotor can be design in variable frequency motor constant power region. Only in this way can reduce the power frequency conversion motor design, cost savings.

The DC speed control circuit is simple, the superior control performance in small power system using the DC speed control cost is relatively low, so the DC in small power simple centrifuge is still widely used in speed. In order to improve the reliability of the drive centrifuge, should as far as possible the use of spindle motor direct drive centrifuge rotor, and centrifuge installation of special requirements and considering the damping system of the whole machine, centrifuge motor general in the spindle forms and shell shape, and other requirements of special design, to meet the special requirements of the centrifuge transmission. If the belt drive or other mechanical transmission, you can choose the standard series of general motors, but the transmission reliability is relatively lower.

Speed control system

1 DC speed

(1) the main loop

There are two main types: DC thyristor rectifier circuit voltage regulation. The DC PWM speed regulator. The characteristics of two kinds of DC speed control circuit is as follows.

1) pwm. DC input using a diode bridge rectifier, high power factor, high frequency modulation, frequency set at around 20 kHz, due to the high frequency, outside the range of human hearing, not only can reduce noise, and can reduce the volume of the filter inductor. The integrated circuit has a variety of PWM waveform generator for use, simple control circuit. But because of the power devices using controllable electronic devices, such as GTR, MOSFET and IGBT etc.. These devices overload capacity is relatively low, to trigger drive circuit requirements high, triggering pulse before and after along to steep, at the same time to fast over-current protection circuit. At present, there have been many kinds of intelligent driver specific integrated circuit came out, it has a variety of automatic protection, which to the wide application of DC PWM speed control system created favorable conditions.

2) SCR Speed control. Thyristor overload capacity is very strong, reliable work. This is one of the reasons of thyristor DC speed regulation still has vitality. The waveform distortion of the thyristor conduction angle changes makes power factor rectifier is reduced, especially in the conduction angle is small, high harmonics, current ripple component, flat wave reactor larger. In the three-phase controlled rectifier, for three-phase transformer phase synchronization, and three trigger pulse forming circuit, complex control circuit. At present, in the domestic and foreign various integrated trigger can be used to enhance the reliability of the circuit. Using full controlled bridge rectifier can improve the commutator spark.

(2) control system

In order to obtain good performance of speed regulation, generally with a double closed-loop control system of speed feedback and current feedback. Double closed-loop control system simulation control and digital control


Related Tags:Othercentrifuges

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