4 Stage Multistage Pump Tripping

Dear Friend,

You have to furnish the capacity of the pump, and before it is tripping - what is the capacity delivered. There could be short-circuiting of Water Flow, with in the stages of the pump, if so the Motor gets loaded but the discharge will fall, heavily.

Pl. check this.

DHAYANANDHAN.S

If you are drawing 117% of full load current with no load, the I would say change the motor for one that isn't knackered, Mildred.

What current does the motor draw if uncoupled from the pump?

Did you check the motor wiring? We had one electrician get a severe reprimand for wiring a 440V motor into a 220V one...and connecting it to 440V. He was lucky to keep his job. (",)

regards,

Vulcan

4 stage PD pump?

At a guess, it has something to do with: "under load we were drawing 125 AMPS" out of a "motor rated at 71AMPS".

It's f@£&#d. Change it.

Pump/bearings may be tight,not free to rotate easily. What was the noload current of the motor without pump. When it takes 83 amps if you say noload was the suction valve closed or discharge valve closed?. Running without water is not good.

The first assignment I had as a field engineer was to investigate pumps which were tripping for motors my company manufactured. I went out and measured current and voltages and called the factory to discuss what I had found. The current was too high and the factory said that the piping leaving the pump was too large. Gut feeling, I thought that the opposite of what the problem was. He was patient with me and explained that horsepower was based on the definition of volume of water pumped through the pump and the height to which it is pumped, from supply to exit of piping. The height was fixed, but the volume could be varied by changing the input or output of the pump. What had happened was the installers had reversed the input and output flanges of the pump. Installing them correctly corrected the problem, by limiting the pump output. Look at the volume pumped and the total height the liquid is pumped to calculate horsepower by the definition of horsepower. (You will have to go back to those Freshman Physics courses you took) If the horsepower does not add up to the power drawn by the pump, then you will have to look elsewhere, but start there. This has answered a lot of field questions over the years. It was counterintuitive that a restriction in the pump circuit would drop the amps, but it did, because the pump was doing less work.

Same counterintuitive thing happen with fans, amps lowered by restricting the inlet.

Now, on the actual matter, please, NEVER restrict the inlet of a pump, even if there is a valve installed (normally for isolation purposes during maintenance).

A 55kw (75 HP) motor at 2950 rpm (2 pole 50 cycle motor) at 550 volts should draw about 72-75 amps. At 380 volts it should draw about 100-105 amps, at 415 v about 96 amps. Sounds like you're either wired incorrectly (wrong voltage) or you're pumping the wrong fluid (water instead of a lighter hydrocarbon with a lesser Specific Gravity) and overloading the driver or the driver was incorrectly sized.

Check all of those things that "don't matter." Some of them do. -- JHF

You want a "4 stage multistage curio pump" manually. Is that right?