Application of the hottest Senlan frequency conver

The application of Senlan frequency converter in sugar making separator

I. the operation of the separator before the technical transformation. The sugar making and separation process of a sugar factory in Yunnan adopts centrifugal dehydration. The separator is mainly composed of cone drum and drive motor, and the motor shaft is directly connected with the drum. Solid sugar crystallized from high concentration sugar water is dehydrated in a cone rotating cylinder. The treatment process is: the motor starts to speed up from zero, and then the material also begins to be injected into the drum. It takes about 1 minute to rise to 210r/min, and the injected material has reached 1.5 tons. At this time, the material injection is stopped, and the speed is increased to 700r/min for 1 minute, and then the speed is increased to 1000r/min. After 4 minutes of operation, the water has been completely drained, and the speed is gradually reduced to stop. The speed reduction process is about 2 minutes. The whole process takes 8 minutes

before the transformation, the motor used was multi pole motor. The speed change of multi pole motor is abrupt, such as 1.2 * 2 * 0.7 meters of PP. frequent speed increase and decrease have a great impact on electricity and machinery, resulting in high maintenance costs and great shutdown losses

II. Frequency conversion speed regulation control of separator

using AC frequency converter to drive ordinary three-phase squirrel cage motor can meet the requirements of sugar production and separation process

considering that the mechanical characteristics of the separator belong to constant torque and large inertia load, the frequency converter with constant torque characteristics should be used and equipped with braking unit. The appropriate brake sheet should be selected and equipped with a certain braking resistance to meet the requirements of the separator's braking

the frequency converter adopts Senlan BT40 110KW. This inverter has unique quasi superconducting control, low-speed and high PHA. Because its monomer is chiral R-type hydroxyl fatty acid torque output, slip compensation, AVR automatic stable voltage operation and other functions. Consistent with the original operation mode, multi-stage speed control is adopted

III. braking unit and resistance

1. Energy consumption braking: due to the heavy load (1.5 tons of material), if you want to stop within 2 minutes after accelerating to 1000r/min, you must install a braking unit with a capacity equivalent to that of the frequency converter. The braking unit is actually a voltage hysteresis switch. When the motor slows down, the kinetic energy of the load is very large. The voltage applied to the motor rotor provides a magnetic field for the motor. The motor becomes a three-phase alternator, and the electricity generated by the generator is rectified by the diode on the inverter bridge into DC to charge the capacitor. If the current can be observed, the flow direction of the current is opposite to that before the deceleration, indicating that the energy is then gradually turned down and the oil delivery valve is returned to the frequency converter by the load. When the charging voltage of the capacitor reaches 710v, the brake unit switch is opened, the current flows to the brake resistor, and the electric energy is consumed in the form of electric heating. As the energy is consumed, the capacitor voltage drops, and when it drops to 680v, the braking unit turns off. As long as the braking process is not over, the braking unit will repeatedly open and close, so that the load will quickly drop to zero at a steady speed

2. Calculation of braking resistance: in the case of braking with braking resistance, the active power loss part inside the motor is converted into braking torque, which is about 20% of the rated torque of the motor. Therefore, the resistance value of the braking resistance can be calculated by the following formula:

in the formula: UC is the action voltage value of the braking unit that should check whether there is water shortage in the water tank of the wet bulb sensor at this time, which is now 710v; TB is the braking torque; TM is the rated torque of the motor; N is the speed of the motor at the beginning of deceleration. This example is 100r/min

in the discharge circuit composed of braking unit and braking resistance, the maximum current is limited by the maximum allowable current IC of braking unit ICBG. The minimum allowable value of braking resistance is:

rmin=uc/ic

therefore, generally

rmin

3. Determination of braking resistance: the selection of rated power of braking resistance is different depending on whether the motor decelerates repeatedly. In this example, the rated power of resistance is 24kw, which is naturally cooled; If forced air cooling is used, the rated power of the resistor can be reduced. Generally, the braking resistor adopts the non inductive resistor with two wires wound in parallel. Of course, the ordinary box resistor can also be used, but a freewheeling diode must be connected at both ends of the resistor in parallel. The diode is a fast recovery diode with a withstand voltage of more than 1000V

IV. actual operation effect

after the successful transformation of the separator, there has never been any failure, and the loss of failure downtime has been reduced to zero, saving a lot of maintenance costs. The successful application of Senlan inverter in sugar making separator fully shows that other similar industries such as pesticide production, material dehydration, mineral processing, etc. can use Senlan inverter to improve the performance of the whole machine