1. Frequency conversion energy saving is known from fluid mechanics. P (power) = Q (flow) ╳ H (pressure), flow Q is proportional to the primary of rotational speed N, pressure H is proportional to the square of rotational speed N, power P and rotational speed N The cube is proportional to the proportional. If the efficiency of the pump is constant, when the required flow rate is required to decrease, the speed N can be proportionally decreased, and at this time, the shaft output power P has a square relationship. That is, the relationship between the power consumption of the pump motor and the rotational speed is approximately proportional. For example, the power of a pump motor is 55KW. When the speed drops to 4/5 of the original speed, the power consumption is 28.16KW, and the power saving is 48.8%. When the speed drops to 1/2 of the original speed, the power consumption is The amount is 6.875KW and the power saving is 87.5%.
2. Power factor compensation Energy-saving reactive power not only increases the line loss and heat of the equipment, but also the power factor decreases, which leads to the reduction of the active power of the power grid. A large amount of reactive power is consumed in the line, the equipment is inefficient and wasteful. By the formula P = S ╳ COSФ, Q = S ╳ SINФ, where S-apparent power, P-active power, Q-reactive power, COSФ-power factor, it can be seen that the larger the COSФ, the larger the active power P, the ordinary The power factor of the pump motor is between 0.6 and 0.7. After using the variable frequency speed control device, due to the internal filter capacitor of the inverter, COSФ≈1 reduces the reactive power loss and increases the active power of the power grid.
3. Soft start energy saving Since the motor is directly started or Y/D start, the starting current is equal to (4-7) times the rated current, which will cause serious impact on the electromechanical equipment and the power supply grid, and will also require too much power grid capacity. The large current and vibration generated during startup are extremely damaging to the baffles and valves, which is extremely detrimental to the service life of equipment and pipelines. After using the variable frequency energy-saving device, the soft start function of the inverter will start the starting current from zero, and the maximum value will not exceed the rated current, which will reduce the impact on the power grid and the power supply capacity, and prolong the use of equipment and valves. life. Saves on equipment maintenance costs.
The inverter can save power. This is an indelible fact. In some cases, it can save more than 40% of electricity, but in some cases it will be wasted than not connected to the inverter.
The inverter is energy-saving through light load step-down. The drag-to-turn load does not change much because of the speed. Even if the voltage is reduced, it will not be much, so the energy saving is very weak, but it is different in the fan environment. At a small air volume moment, the motor will reduce the speed. We know that the energy consumption of the fan is proportional to the 1.7th power of the speed, so the torque of the motor will drop sharply and the energy saving effect will be obvious. If we use it on the oil well, it will waste more electricity because it uses a lot of power in the return stroke.
Of course, if the environmental requirements must be adjusted, the energy-saving effect of the inverter is still obvious. In the case of no speed regulation, the inverter will not save power and can only improve the power factor.
(1) If two identical motors are operated at a power frequency of 50 Hz, one uses the inverter, one does not, and the speed and torque are both at the rated state of the motor, can the inverter save power? How much can I save?
A: For this situation, the inverter can only improve the power factor and does not save power.
(2) If the torque of these two motors does not reach the rated torque of the motor (frequency, the speed is still the same 50HZ), how much electricity can save the inverter?
Answer: If automatic energy-saving operation is used, the inverter can be stepped down at this time, which can save part of the power, but the power saving is not obvious.
(3) The same conditions, how much can be saved under no-load conditions, which provinces are more in these three states?
A: The drag-type load no-load state can not save much power.
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