Small agricultural pump power and heat are two. The former is generally three-phase or single-phase motor, which is a diesel engine. After the pump model is selected, select the power according to the following requirements:
1, the type of choice According to the local power supply, reliable power supply area should be selected motor, the general selection of squirrel cage type, only in the power grid capacity is small, not enough to ensure the squirrel cage motor start case before considering the winding type . In the dry, dusty place with a protective type; in the dusty, splashing closed with closed; immersion work can be sealed. When the pumping load continuously and evenly, the motor should be continuous working system, its speed should be consistent with the pump, easy to start directly, or you can choose to use the speed closer to the indirect transmission.
2, the power of choice Strictly speaking for the pump matching power machine need to go through scientific calculations, but for small farm pump motor selection based on past experience on it, the average motor power should be equal to the required pump power 1.0 ~ 1.3 times the internal combustion engine should be equal to 1.3 ~ 1.5 times the power required for supporting agricultural machinery, too big a horse car to waste energy is too small, it is easy to take fixed or overload damage to the power machine. If you have already bought some power equipment in advance, you should give full play to the role of the existing power machine, in the purchase of new agricultural pumps, we should try to be able to match with the original power machine, in addition to special needs, generally do not have each machine alone A power machine, so cost too much, management is not convenient. In stationary units, the motor can be used at 75% to 100% of its rated power range; a diesel engine with a full speed governor reduces speed and power usage in its speed range.
3, the choice of rated speed Motor rated speed according to the requirements of the pump. However, the asynchronous motor usually synchronous speed of not less than 500r / min, therefore, requires low speed pumps need deceleration device. Because the asynchronous motor under the same conditions of power, the lower the synchronous speed, the greater its electromagnetic torque, the greater the volume, the heavier the weight, the more expensive the price, therefore, the choice of high-speed motor is more economical, so under normal circumstances As far as possible the use of high-speed induction motor, such as the pole number P = 1 or 2 and so on.
4, the rated voltage of the selected motor The rated voltage of the selected motor should be consistent with the voltage of the power supply grid. The voltage applied to a three-phase asynchronous motor will work normally within the range of + 10% to -5% of its rated voltage. Low-voltage power grid voltage in the countryside is 220 / 380V, so small and medium-sized asynchronous motors used in rural areas are low-voltage, usually single-phase motor rated voltage of 220V. Three-phase motor rated voltage 380V, Δ connection. This three-phase motor has two advantages, one can use Y / Δ buck start. Because when the motor rated power reaches one-third of the transformer capacity, this motor must be buck-start. Second, a dual-use machine. Method is to take the three-phase asynchronous motor winding connected to a star in the 380V power supply, then the motor power is about 34% of rated power.
Lastly, it needs to be emphasized that the three-phase motor must be selected in rural areas where there is three-phase power supply. This is because the three-phase asynchronous motor has the advantages of small size and weight compared with single-phase asynchronous motor under the same power conditions Light, small vibration, low price, less power consumption and so on.
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