Vertical 300hp Well Pump Motor

[Ingenieur]

mechanical binding seems likely

drive starts motor
ramps to 15 Hz
current climbs as it ramps to 20 Hz
reaches a limit and backs off
like it is trying to start a high inertia load by increasing current/torque
but as rpm increases it hits a limit
the fact that it is always in 'accel' mode seems to confirm
especially since ramp time is only 2.5 sec

who aligned/coupled the pump?
use a laser?
shim everything,
check it after completed?

what is the motor speed? 1800, 3600?
is the vfd set up for the correct speed?

 

[adamscb]

mechanical binding seems likely

drive starts motor
ramps to 15 Hz
current climbs as it ramps to 20 Hz
reaches a limit and backs off
like it is trying to start a high inertia load by increasing current/torque
but as rpm increases it hits a limit
the fact that it is always in 'accel' mode seems to confirm
especially since ramp time is only 2.5 sec

who aligned/coupled the pump?
use a laser?
shim everything,
check it after completed?

what is the motor speed? 1800, 3600?
is the vfd set up for the correct speed?

Motor nameplate RPM was entered into the VFD properly (1785 rpm), and I can't speak for how it was coupled up, that's beyond my realm. Before leaving work Friday I mentioned that the pump should be checked, this is what I'm starting to believe as well. And to me it seems like it's not turning at all. But I find that odd because if the rotor was completely locked I would think the breaker would trip, which isn't happening. Could be possible that the VFD keeps trying to ramp up, but then backs off, and rinse/repeat.

 

[Ingenieur]

Motor nameplate RPM was entered into the VFD properly (1785 rpm), and I can't speak for how it was coupled up, that's beyond my realm. Before leaving work Friday I mentioned that the pump should be checked, this is what I'm starting to believe as well. And to me it seems like it's not turning at all. But I find that odd because if the rotor was completely locked I would think the breaker would trip, which isn't happening. Could be possible that the VFD keeps trying to ramp up, but then backs off, and rinse/repeat.

the cb may not trip
the vfd limits current, so a lr magnitude current is not possible
what size cb feeds this vfd? 800, 1000?
can't you see the motor?
even if v out = 150 at 250 A ~ 0.6 Ohm, almost like winding Z

the confusing part is the 20 A in vs 250 out

 

[GeorgeB]

the confusing part is the 20 A in vs 250 out

If the motor is not turning, there is "no" power to the pump ... even though there is high output current. Input current indicates that condition. I'm with those thinking a shaft is binding or a reverse clutch is installed backwards.

 

[Ingenieur]

If the motor is not turning, there is "no" power to the pump ... even though there is high output current. Input current indicates that condition. I'm with those thinking a shaft is binding or a reverse clutch is installed backwards.

he measured 250 A to the pump
likely at 150 V
65 kva
at lr pf 0.1-0.2 or greater
so 7-13 kw

input kva 17 kva at 0.90 or better 15 kw

I guess that makes sense
assuming the motor was lr

what pump type?
he said centrifugal 'vertical well pump'
vertical turbine?
usually the motor and shaft are visable

 

[ptonsparky]

Sounds like it’s trying to run the the wrong direction.

 

[Dzboyce]

Questions;

exactly what kind of vertical pump is this? Lineshaft turbine pump with hollowshaft motor? Close coupled centrifugal? Other?

Was motor rotation checked checked before clutching it up? If this is a lineshaft turbine and it was run backwards, the shaft could have unscrewed and the impellers are dragging in the bowls.

 

[Jraef]

Just to toss one out there. I started some once and experienced something similar. The shaft was visible and turning, but slowly. In this case we also had soft starters as the bypass for the VFDs and when we tried starting it that way, the breakers did trip. The VFD was artificially suppressing the current rise from the locked rotor, something the soft starter could not replicate. As expensive as it was to pull the pump, it turned out to be a coupling in the shaft that used set screws, and one of the set screws was over tightened to where it was rubbing against something (I wasn’t there when they found it so I don’t totally understand that).

The point is, the VFD’s ability to current limit continuously was masking the mechanical problem that became obvious when the motor was powered without it. Even the soft starter’s current limiting capabilities couldn’t do the same thing.

 

[kwired]

Motor nameplate RPM was entered into the VFD properly (1785 rpm), and I can't speak for how it was coupled up, that's beyond my realm. Before leaving work Friday I mentioned that the pump should be checked, this is what I'm starting to believe as well. And to me it seems like it's not turning at all. But I find that odd because if the rotor was completely locked I would think the breaker would trip, which isn't happening. Could be possible that the VFD keeps trying to ramp up, but then backs off, and rinse/repeat.

Breaker in supply circuit is not going to trip if you are only ramping up to 15-20 HZ. Drive should trip on overload or other voltage/current related issues well before input current gets into trip zone of supply breaker.

Across the line, wye-delta or non electronic reduced voltage starting methods may trip input breaker before motor overload device trips if motor will not turn.

 

[Sahib]

Across the line, wye-delta or non electronic reduced voltage starting methods may trip input breaker before motor overload device trips if motor will not turn.

The motor overload device would be damaged if it tries to break locked rotor current.

 

[kwired]

The motor overload device would be damaged if it tries to break locked rotor current.

If direct acting probably so. Most of the time, and especially on this large of a motor, motor overload device monitors motor line conductors, but breaks a control circuit.

 

[Jraef]

The motor overload device would be damaged if it tries to break locked rotor current.

The VFD itself IS the motor protective device, and because it is artificially limiting current, it is not tripping YET, but likely would eventually if he had allowed it to continue running. I believe our OP is wisely not keeping it running when he is observing something so egregiously wrong...

Let's try to steer clear of tangential non-sequiturs.

 

[Sahib]

May be speed reference control signal is lost. Check alarm status.

 

[Besoeker]

the confusing part is the 20 A in vs 250 out

Different power factors.
Yes, it could be a locked rotor.
But this strays from the initial point and I have already been admonished for that.

 

[Sahib]

Yes, it could be a locked rotor.

The drive would have shut down then.

 

[Besoeker]

The drive would have shut down then.

Couldn't it have just sat there in current limit? Depending on the settings?

 

[Sahib]

Couldn't it have just sat there in current limit? Depending on the settings?

Could not it be checked it is so?

 

[Sahib]

Couldn't it have just sat there in current limit? Depending on the settings?

Perhaps another safety feature of drive would kick in: Shut down due to excess start time.

 

[Besoeker]

Perhaps another safety feature of drive would kick in: Shut down due to excess start time.

If it has such a feature and it is enabled, then possible I suppose. That said, I've seen drives sit in current limit. Mechanically coupled sections on a paper machine is one that sticks in my mind.

 

[Jraef]

The default setting of that particular drive is for it to attempt to stay running by driving down the frequency and lowering the current limit. If the user did not change that setting (and it sounds probable), that would completely justify what he is seeing. So really, what we DON'T know is why it is a perpetual state of overload. It cannot be that the motor is overloaded from flow, there is none. So it leaves a mechanical problem or a defective drive, and he has run the motor uncoupled from the pump with no issue. I'm going with a mechanical problem here.

Parameter 430, Drive OL Mode
Drive Overload Mode; Selects the action to take when the drive detects that it is being overloaded. Reducing current limit and / or PWM frequency may allow the drive to continue running without faulting. When using a sine wave output filter, set this parameter to 1 “Reduce CLmt” or 0 “Disabled.”
Default: 3 = “Both PWM 1st”
Options:
0 = “Disabled”
1 = “Reduce CLmt”
2 = “Reduce PWM”
3 = “Both PWM 1st”