Development status of high voltage motor speed control technology
Introduction: The inverter is a low-voltage inverter. The input side uses a transformer to change the high voltage to a low voltage. The high-voltage motor is replaced. A special low-voltage motor is used. The voltage level of the motor is various and there is no uniform standard.
From the current market situation, it can be divided into the following types:
Hydraulic Coupler
An impeller is added between the motor shaft and the load shaft to adjust the pressure of the liquid (generally oil) between the impellers to achieve the purpose of adjusting the load speed. This kind of speed regulation method is essentially a slip power consumption type. The main disadvantage is that as the speed of the speed decreases, the efficiency of the motor and the load needs to be disconnected for installation and maintenance. Parts such as shaft seals and bearings are replaced. The site is generally dirty, which appears to be low in equipment and is a phase-out technique.
Early manufacturers interested in speed control technology, or because there is no high-pressure speed control technology can choose, or take into account the cost factor, there are some applications for hydraulic couplers. Such as the water pump of the water company, the boiler feed water pump and the induced draft fan of the power plant, and the dust removal fan of the steel mill. Now, some old equipment has gradually been replaced in the transformation.
High and low high frequency inverter
The frequency converter is a low-voltage frequency converter, which uses an input step-down transformer and an output step-up transformer to realize the interface with the high-voltage power grid and the motor. This is a transitional technology when the high-voltage frequency conversion technology is not mature.
Due to the low voltage of the low-voltage inverter, the current cannot rise unrestricted, which limits the capacity of the inverter. Due to the existence of the output transformer, the efficiency of the system is reduced, and the floor space is increased. In addition, the magnetic coupling capability of the output transformer is weakened at low frequencies, so that the load capacity of the inverter is weakened at startup. The harmonics of the power grid are large. If 12-pulse rectification is used, the harmonics can be reduced, but the strict requirements for harmonics cannot be met. When the output transformer is boosted, the dv/dt generated by the inverter is equally amplified, and filtering must be added. The device can be applied to ordinary motors, otherwise corona discharge and insulation damage will occur. This can be avoided if a special variable frequency motor is used, but it is better to use a high and low frequency converter.
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