Centrifugal pump is conveying acid of sulfuric acid, alkali, salt and other corrosive medium centrifugal water pump
, usually with fluorine plastic centrifugal pump, stainless steel centrifugal pump, centrifugal pump viscous medium concentration of sulfuric acid, the proportion of high fluid, some users in the selection of centrifugal pump, due to various reasons is not complete, such as customer itself for motor and buy only when buying a water pump pump head;
Or before using the rest of the pump, the motor power is smaller than now, think the pump motor power consumption, and the power can be used as before.
Often these situations, sulfuric acid centrifugal pump motor instantaneously burned at startup, then what's the problem?
One, the instantaneous current of motor starting current when the motor first starts, however, refers to the motor connected to the rated voltage starting from zero speed when the input line current.
Motor starting current is commonly the rated current of the 5 ~ 7 times.
One is a saying says in starting the moment (
The start-up process of the initial moment)
Motor speed to zero, then the current value should be its locked-rotor current value.
We often use for the Y series three-phase asynchronous motor, in JB/T 10391 & ndash;
2002 standard for Y series three-phase asynchronous motor are clearly defined.
Stalling a 5 kw motor current and e. as follows: the ratio of the rated current of synchronous speed 3000, locked-rotor electric current and the ratio of the rated current of 7.
The synchronous speed 1500, locked-rotor electric current and the ratio of the rated current of 7.
The synchronous speed 1000, locked-rotor electric current and the ratio of the rated current is 6.
The synchronous speed 750, locked-rotor electric current and the ratio of the rated current is 6.
5 kw motor power is larger, in small power motor starting current and the rated current ratio is smaller, so the electrician materials and said a lot of places are asynchronous motor starting current is rated current of 4 ~ 7 times.
So when the motor pneumatic frequently, due to the accumulation of heat, can lead to motor overheating.
In addition, excessive motor starting current in a short period of time can cause larger voltage drop, online way and make the load voltage is reduced, affect the normal work of the adjacent load.
Motor at startup, not a fixed value, in the process of motor starting, from big to small changes in the current, is the reciprocal function of time (
And there is no specific formula.
Basic not just plug in the electrical impedance, only impedance, also is the dc resistance of the coil, this number is very small, so the instantaneous current is very big, can be rated current of dozens of times, but the duration is very short, usually only zero point zero seconds.
As the rotating motor, the current fell sharply, if you don't load startup, will be in 1 seconds to around 10 times the rated current, along with the speed rise, can drop to 2 - after 2 seconds
Continue to fall, after three times, until it is equal to the rated current, the motor speed also rose to rated speed.
So, motor starting current is refers to the average.
Because different machine, different load and different ways of start, start time required is not the same, there is big difference between the average current.
Two centrifugal water pump motor start burned solution of sulfuric acid, 1, according to the requirements of factory configuration corresponding motor power or USES frequency conversion motor, installing frequency conversion device.
2, start the motor series resistance, which is a method of step-down start.
In the process of start, series resistance in the circuit of the stator winding, when starting current through the voltage drop on the resistance, the reduced on stator winding of voltage, so that you can achieve reduce the starting current.
3, the use of autotransformer tapped the reduced pressure, can adapt to the needs of different load starting, and can get a bigger starting torque, is a kind of is often used to starting decompression of the large capacity motor starting.
It has the advantage of starting torque is bigger, when the tap at 80%, starting torque can be up to 64% of the direct starting and can adjust the starting torque by tapping.
4, frequency converter is the modern high technical content in the field of motor control, control function, control the motor control device with good effect, it is by changing the frequency of the power grid to adjust the rotation speed and torque of the motor.
Because of involving power electronic technology, computer technology, so the cost is high, too high to the requirement of maintenance technicians, mainly used in need speed and the field of high speed control requirements. water pump
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