Delta/wye, with a HRG system on the low-voltage side. I made sure to configure the drive grounding jumpers for a high-resistive grounded system. We had an issue with that with some drives in our plant - there was a ground fault on the system, and the drive grounding jumpers weren't set up properly. It ended up frying every drive in the MCC - about half a dozen or so. One of those lessons you don't forget.
Vertical 300hp Well Pump Motor
- Thread starter adamscb
- Start date
- Status
Delta/wye, with a HRG system on the low-voltage side. I made sure to configure the drive grounding jumpers for a high-resistive grounded system. We had an issue with that with some drives in our plant - there was a ground fault on the system, and the drive grounding jumpers weren't set up properly. It ended up frying every drive in the MCC - about half a dozen or so. One of those lessons you don't forget.
I believe it limits the GF current to 5 amps, and we have it set up so the system stays on-line, but we would have to find the fault and then shut down the culprit.
https://www.postglover.com/download...7Hj0da5TMumeFhE7eLoTyIdpZrX399OXSrx1J4xEYlrai
that is low, but safer
55 Ohm ngr
if ground loop (conductor and fault) is say 2 Ohms frame v-g is 10 v
should not cause any damage or shock hazard
be aware though, while operating under fault unfaulted ph-g voltages are elevated by sqrt3 or to 480 (from 277)
not an issue with 600 vac insulation
some cb's are rated for only 277-gnd though
Last edited:
But a centrifugal pump motor will be overloaded if it is run above its full load speed by VFD!
kwired
Electron manager
- Location
- NE Nebraska
Can be overloaded, you could restrict inlet/outlet to bring the flow (and load on the motor) down.
ptonsparky
Tom
- Occupation
- EC - retired
I have a small suspicion that maybe Jraef might possibly understand that.
May be over voltage issue inherent in ungrounded system might be the cause of damage in OP case due to poor grounding in his HRG system!
it is sort of self limiting
as flow increases so does head friction
visualize a pump curve and the system curve with the power curve on the flow axis
using the affinity law the pump curve is elevated parallel
the system curve remains the same
although the intersection/operating point moves, it does so diagonally
so flow increases as does head
the system curve is typically steep approaching vertical in this region
so you get a small flow increase but large head increase
flow ~linear, head^2 with speed
easier with a picture
I need to do last minute Christmas shopping, perhaps later lol
kwired
Electron manager
- Location
- NE Nebraska
You have another day before "last minute" starts to kick in
can be dangerous
we use a 15 A ngr for lv and 25 for mv
we monitor the egc and if >2.7 Ohm (corrosion, damage, vibration/loose) trip the mcb with a uv coil
the ckt is all nc, normally energized fail safe, a broken wire anywhere shuts it down
You have another day before "last minute" starts to kick in
church, family crap and lounging planned for tomorrow
many stores in my small town are closed tomorrow
the gall of those businesses to inconvenience me so their employees have Christmas eve Sunday off lol
I assume I don't need a dynamic braking resistor for this VFD application? The pump comes to a stop via coast pretty quickly. Am I thinking correctly here when/when not to apply a DBR, is the time it takes the load to come to a complete stop?
Also what about an encoder? I'm under the impression an encoder is needed when the drive needs to know what exact speed the motor is currently running at. I wouldn't think I'd need one of these, unless I was doing a PID loop inside the drive, which I'm not.
Are there any other VFD accessories I'm missing? We've got line/load reactors, DBR's, encoders...anything else? Thanks.
Also what about an encoder? I'm under the impression an encoder is needed when the drive needs to know what exact speed the motor is currently running at. I wouldn't think I'd need one of these, unless I was doing a PID loop inside the drive, which I'm not.
Are there any other VFD accessories I'm missing? We've got line/load reactors, DBR's, encoders...anything else? Thanks.
Last edited:
braking is usually required when load inertia is involved and energy needs dissipated and the motor will be stopped holding the load
not required for pumps
as you noted when you need speed or position feedback an encoder may be required
for pump no
your feedback is pressure, it will modulate pump speed
not required for pumps
as you noted when you need speed or position feedback an encoder may be required
for pump no
your feedback is pressure, it will modulate pump speed
- Location
- San Francisco Bay Area, CA, USA
- Occupation
- Electrical Engineer
Line reactors help protect the relatively large investment in the VFD. I always recommend a line reactor if your source transformer is more than 10x the kVA of the VFD. From post #40 you are right there at around 10%, maybe a tad over. Personally I would add a 3% line reactor, it's cheap insurance.
Load reactors help protect the motor for the most part, but can also help protect the drive when there is a high risk of circuit damage in the motor or leads. I would classify a vertical pump station application as low risk of load circuit damage, so a load reactor would be unnecessary. DV/DT filters are better at protecting the motor and since you said you might do that anyway, that will include a load reactor in it so you get the other benefits anyway. I know you said you will be using an inverter duty motor but honestly, there is no official definition of that term, and a LOT of motor mfrs. have taken to using very loose interpretations. A DV/DT filter is then also cheap insurance against that possibility. But too many devices like that in a circuit can cut down on the maximum motor voltage, robbing you of full torque. If the pump is indeed going to require the peak capacity of the motor, you may want to reconsider that. See if the pump supplier can give you the HP requirement at full load and head. If it's under 270HP, put anything you like in that drive circuit...
And yes, per what Ingenieur said, no need for braking or encoders on a centrifugal pump. Just use the drive in V/Hz mode, it's simpler.
Load reactors help protect the motor for the most part, but can also help protect the drive when there is a high risk of circuit damage in the motor or leads. I would classify a vertical pump station application as low risk of load circuit damage, so a load reactor would be unnecessary. DV/DT filters are better at protecting the motor and since you said you might do that anyway, that will include a load reactor in it so you get the other benefits anyway. I know you said you will be using an inverter duty motor but honestly, there is no official definition of that term, and a LOT of motor mfrs. have taken to using very loose interpretations. A DV/DT filter is then also cheap insurance against that possibility. But too many devices like that in a circuit can cut down on the maximum motor voltage, robbing you of full torque. If the pump is indeed going to require the peak capacity of the motor, you may want to reconsider that. See if the pump supplier can give you the HP requirement at full load and head. If it's under 270HP, put anything you like in that drive circuit...
And yes, per what Ingenieur said, no need for braking or encoders on a centrifugal pump. Just use the drive in V/Hz mode, it's simpler.
It may be designed to run above "synchronous" speed. We have done a few like that. Not just pumps but steel mill roller tables and textile machines.
I bet that is for short time duty and not for continuous duty as in OP case
.
ptonsparky
Tom
- Occupation
- EC - retired
Comparing Oranges to Tangerines. OPs 300 hp vs fractional plus a bit.I bet that is for short time duty and not for continuous duty as in OP case
My well guy says they use smaller HP submersibles and overdrive them for more GPM as needed. Designed from the start for this purpose of course.
You mean with service factor?
- Status