3 Phase Motor Current Draw HIGH 3

[tlona]

We have an inline pump with a 150HP/3 phase 460V, 165A nameplate vertical motor, Delta Start, Delta Run (6 leads). The pump and motor were out of service for over a year and recently serviced and moved to a new installation at a different facility. The new installation is a similar application in that it is being used for the transfer of #6oil between two bulk storage tanks. We are using an Allen Bradley SMC Flex Soft Start. We have the start and run leads wired in parallel. The motor starts and comes up to speed but is drawing about 215Amps when running ruinning at its normal operating point (2000gpm @ 200ft head). When we choke down on flow the current drops but to about 190A but can never get it to the 165A. The motor is a RELIANCE Motor from 1994. I obtained the factory information from the nameplate serial number. The factory cut sheet states a 208V motor. I just noticed that the current nameplate was originally stamped for 208V but then 'XX' out and re-stamped for 460V. Could this voltage conversion/rewinding be the cause of the issue?

 

[itsmoked]

Thanks Hutz.

I missed that too Bill. Thanks edison for reminding us.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[tlona]

Thank-you all for the feedback and am investigating all suggestions. I will be looking at a spare siemens (RGZZVILESD) motor to see it it has the standard 6 leads that we can wire "Inside the Delta". This type of installation recommends a shunt trip on the Main CB. Does anyone know if the Main CB also needs to be resized for this type of installation. Cant seem to find it in the Allen Bradley SMC Flex Literature.

 

[waross]

Beware of assumetions!

We have an inline pump with a 150HP/3 phase 460V, 165A nameplate vertical motor, Delta Start, Delta Run (6 leads).

I see no indication that the motor is connected in delta internally.

I will be looking at a spare siemens (RGZZVILESD) motor to see it it has the standard 6 leads that we can wire "Inside the Delta"

Six leads is standard in Europe. Star-Delta
Nine Leads is standard in North America. Series-Parallel.
There are exceptions.
A six lead Part Winding Start motor may be wired as either star or delta internally.
A six lead part Winding Start motor is not the same as a six lead Star Delta motor.
Not interchangeable.
Connecting a soft start "inside the delta" normally requires the delta connection to be made externally to the motor.
Most of the North American motors that I see are star connected.
If a NEMA motor is delta connected, there are three internal connections that are not available for "inside the delta" connection.
Have you compared the normal suction head at the new site with the normal suction head at the original site?
If you are transferring a full tank to an empty tank, the suction head will be high and the discharge head will be low.
Motor current may be at the maximum.
As product is transferred the suction head will decrease and the discharge head will increase.
The motor current may be dropping.
I use the word may as there may be unexpected effects due to dynamic heads and pump curves.
It may be time to review the suction head.


Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[jraef]

The breaker will still see all of the motor current, so it must be the same size no matter how you connect the soft starter.

The ONLY purpose for the “inside the delta” configuration is to be able to use a smaller (cheaper) soft starter by taking advantage of the way a Wye-Delta motor is wound, because by putting the individual power poles of the soft start in series with each set of windings, only 58% of the current passes through the soft start. If your soft starter is already sized for the full motor current, don’t do this. It confuses 99% of the people who see it later and leads to a LOT more problems in the field than it solves. And again, it ONLY works for motors wound for Wye-Delta starting, not Part Winding.


" We are all here on earth to help others; what on earth the others are here for I don't know." -- W. H. Auden

 

[waross]

Hi Jeff; Outside the box, but with a nine lead motor internally connected in delta, is it possible to use an inside the delta connection in place of the 4-7, 5-8 and 6-9 jumpers.
The control power for the soft start would have to be rewired of course.

Keith; Think of a 100 HP part winding start motor as two 50 HP motors working together.
If a fan requires 100 HP, the start winding will be at 200% load as it comes up to speed.
Starting surge plus 200% load, your judgement.
1 second seems short but safe.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[itsmoked]

Good way to look at Bill. Thanks.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[LittleInch]

I'm with Edison 123 here. This seems to me to be related to the load. A fixed speed motor will take what it needs to maintain the pump speed.

We've already established that at its rated point ( 2000gpm @ 200ft head differnetial), with the liquid tar you seem to be trying to move, the efficiency of the pump will decrease and hence power increase by 10-15% easily compared to the values on the pump data sheet obtained when pumping WATER - because that's how pumps are tested. This is the key information I believe, not the electrical stuff.

"I dont know what the current was uncoupled as we received the call from the electrician who stated that it ran fine uncoupled but drew high current when coupled and flowing product. We have a gate valve on the discharge and when first started and up to run speed the motor drew about 260amps with about a 60psig delta so we "choked down" on the gate valve to get the 90psi delta and the amps dropped. The more we "choked on the gate" the amps dropped but never to the rated current. We also never deadheaded the motor. We are actually gonna drain and do a no load test next week. Based on our run time and tank levels we were able to obtain a flow rate which matched the pump curve head. "

At 60 psi delta you were off the end of the pump curve big time and hence power was a lot higher. A gate valve is not a good throttling device and even a few psi difference over the 200 ft (~ 87 psi) will make a difference with the decreased efficiency. Also flowrates over time would vary as the tank levels change.

"We are actually gonna drain and do a no load test next week." - Please don't run the pump empty [If I've interpreted that correctly] - you could easily destroy it and the bearings and seals. You can dead head the pump (not the motor) for a short while as this will give you the lowest current and then slowly increase flow watching your current. But a Gate valve won't last long in this duty and is quite a brutal way to throttle flow. A few percent difference in open will make a big jump in flow / current. If this is a permanent arrangement best to fit an orifice plate or a proper globe valve / control valve to do this.



Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[LionelHutz]

I would still check the no load current because the electricians "running fine" doesn't meant the current was running where it should have been at about 30% to 40% of the FLA. I've seen motors being tested that had the no load current very close to FLA. Sure, they ran fine unloaded, but I wouldn't even bother trying applying a load to a motor that did that.

 

[tlona]

Thank-you for the feed back. Yes agreed on the gate valve as it was not the intent to use it as a throttling device and are looking into an orifice plate. The pump curve was obtained from the vendor for 6oil and the previous application was 6 oil. Since different installation suspected that the load could have increased and inquired if the motor was improperly would cause an increase in current draw.

 

[LittleInch]

Fair enough nd thanks for response.

What you may need to ask to close the loop is ask if they were ever able to pump at 2000GPM in the previous location or what temperature they pumped at compared to the new location. If they only ever got to 1500 GPM then they would be within the load of the motor. Very rarely are two locations ever exactly the same.

It also looks like there are actually different types of no 6 Fuel Oil, but "Liquid tar" seems to be a fairly apt description for them all, but some are less liquid than others.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[edison123]

Lionel - Have serviced quite a few high torque motors (hoist, winch, mill, compressor) with OEM windings that took nearly 80 to 90% of FLA in decoupled condition. They all are running fine at full load without exceeding rated current.

Muthu

http://www.edison.co.in

 

[itsmoked]

The power factor seems pretty hard to estimate between various motors. If it drops to 0.2 or 0.1 you could see some really misleading clamp-on readings. Too bad it isn't easier/cheaper to clamp-on a wattmeter - which would be way more informative.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[LionelHutz]

I once ran across a motor that "Ran fine" uncoupled. Of course, it almost caught fire coupled even though it also "ran fine" coupled. When our service tech arrived about 2 hours after it had failed the motor still couldn't be touched.

 

[edison123]

Lionel - Again, "caught fire coupled" is more of a load problem, not a motor problem. Any thermal related issue/failure of motor is solely due to load or lack of adequate cooling.

Keith - AC motor no-load pf is very poor, being less than 0.1. Most commercial wattmeters and power analysers kick the bucket at around 0.5 at the max. I had to shell out quite a bit to design a power analyser for my shop to measure very low motor no-load pf with multiple time samplings of instantaneous voltage and current and some expensive software to arrive at the correct pf and watts, var etc, but it was money well spent. Clamp-on ammeters on non-VFD motors have no issues measuring the no-load current. It's VFD ones that is pita for clamp-ons.

Muthu

http://www.edison.co.in

 

[tlona]

Thanks again for all of the feedback. At the moment, will be replacing the spare siemens motor just to rule out if is a motor issue. If all motor and/or any electrical issue are ruled out then will have to conclude that the new product and piping configuration are such that more HP is required. The terminal can weight the options of investing in a larger larger motor/pump or attempt to reduce capacity on the existing pump. Will post results.

 

[electricpete]

Did you ever check if the oil is cooler in the new installation? (cooler oil has higher viscosity and requires more pumping power).


=====================================
(2B)+(2B)' ?

 

[LionelHutz]

Lionel - Again, "caught fire coupled" is more of a load problem, not a motor problem. Any thermal related issue/failure of motor is solely due to load or lack of adequate cooling.

WRONG, IT WAS NOT A LOAD PROBLEM OR COOLING PROBLEM. The motor burned up without exceeding the FLA. It was also clean, environment was <30*C and the fan was working. It happened, accept it.

 

[tlona]

Update. Ultimately ended up shaving the impeller by 7/8". Now system is working within acceptable limits even with the reduce flow and head. And yes while they are calling it 6 oil, it is various grades with various viscosity's. So have to point to this along with probably some poor efficiency. Thank-you for all of the feed back. Great website

 

[LittleInch]

So it was the load after all.

Thanks for the update.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[Artisi]

A bit of a change for once, the first thought to most people is always "there is something wrong with the pump" guess this time it was half-true, although there wasn't anything wrong with the pump, just the way it was being used .

It is a capital mistake to theorise before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts. (Sherlock Holmes - A Scandal in Bohemia.)