variable speed motor control

[Bert]

Hi All

I need to find a solution to a problem with a water tank and pump, I have a tank with a gravity flow inlet and pumped outlet, I want the pump to pump out the tank as slow as possible (for process reason) but i dont want to over fill the tank. So what I am thinking is using a fluid level sensor to monitor the fluid level in the tank, If the tank is beginning to over fill then the motor rpm will increase and if the tank is lets say about half full then the motor will slow down keeping the fliud in the tank as long as possible but not stopping until the tank is empty. There is not a consistent flow of liquid into the tank as it comes in gushes and then stops etc, Currenlty there is an 220 volt AC 50hz motor attached to the pump. I would welcome any feedback as to would this system work and can my motor be retrofitted with a circuit from a fluid sensor?

[SHAH DISHANT H.]

Hi,

 

To control speed of AC motor, we need to use TRIAC drive. You can also use IGBT Driver to drive motor at variable speed.

[Ashutosh Bhatt]

for ur application u need to build Variable Frequency Drive VFD. that will give variable voltage to pump so that its speed will vary. a resistive type flow sensor can be used whose resistance inc/dec as tank level inc/dec. apply bias to this sensor will give variable voltage output. using ADC convert this into digital. now as per this digital value inc/dec motor speed using VFD.

[Bert]

Hi , Thanks for  your replies, Am I correct in saying VFD cannot be used on single phase motors?

[Ashutosh Bhatt]

1 phase VFD are also there. i know speed control of 1 phase AC motor is done through varying phase angle using DIAC-TRIAC method. but its applicable in fan, blower, cooler, heater kind of application where load on motor is limited. 

in pump type application i dont think it will work.  

[Author]

Posts