hot running motor
hot running motor
(OP)
i have recently connected a star delta motor. it starts up and runs fine but it it is running quite hot. when i checked the current reading for each phase i found the following; red was 3.5A yellow was 4A and blue was 4.5A
i felt that this was not normal ie they should all be the same the motor is a grundfos lpo80-125-133 at 4kw pumping 80 tonnes per min can any one help me
Cheers steve
i felt that this was not normal ie they should all be the same the motor is a grundfos lpo80-125-133 at 4kw pumping 80 tonnes per min can any one help me
Cheers steve





RE: hot running motor
yours
RE: hot running motor
RE: hot running motor
RE: hot running motor
re; 80 tonnes per minute. I saw a gravity loading installation for gasoline. A 300 kw pump was added to reduce loading times. The pumping rate was nowhere near 80 tonnes per minute.
respectfully
RE: hot running motor
steve
RE: hot running motor
80 tonnes per minute? i suggest to re-check this figure.
With due respect, you're doing such measurement impractical.
Try using available temperature measuring instrument to obtain a quantitative values for you to validate your query as you refered as "HOT".
In condition monitoring, we often measure the temperature of the machine from "cold start" up to "running condition". A temperature data of such machine will most likely stabilizes at a certain temperature, considering the other parameters is normal.
RE: hot running motor
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Sometimes I only open my mouth to swap feet...
RE: hot running motor
I also question the 80 tonnes/minute number. Danfoss make implies that it is water. What head? Must be very low (negative, I would say) if you have that flow at 4 kW.
Gunnar Englund
www.gke.org
RE: hot running motor
I think you are getting your Foss`s mixed up my friend. Danfoss do the inverters, Grundfos do the pumps......I did it once myself in a quote document....very embarassing.
Steve? Why not contact Grundfos direct and ask them what the max allowable surface temp should be for your conditions. They have a habit of painting their kit black which doesnt help in hot enviroments
http://www.grundfos.com/web/grfosweb.nsf/
RE: hot running motor
If you do conclude it's hotter than expected.
Maybe measure the current and compare it to nameplate.
1 - check for correct and balanced voltage as mentioned by waross.
2 - check mechanical load is not too high.
3 - check connections are correct.
By the way you told us the currents but not that voltage. What is the system voltage or the nameplate FLA?
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RE: hot running motor
RE: hot running motor
Ask the person who gave you the 80 tonne/minute figure if the pump is able to fill a large tank truck in 15 seconds flat.
respectfully.
RE: hot running motor
Gunnar Englund
www.gke.org
RE: hot running motor
NEMA Standards MG 1-14.35 indicates derating a motor's HP rating by 25% with a 5% voltage imbalance.
RE: hot running motor
they are mainly swimming pool motors i get called out to, this particular one is quite large.
i have emailed grundfoss directly but no reply as yet.
any how i will visit the pump today and get all the details and and check every thing you have all suggested i have managed to borrow a heat probe which will give me a more accurate temprature reading.
maybe one of you kind gentlemen could explain to me the principle of overload protection and how to set them up correctly as i feel that they are not always set right, and to clarify my own thoughts.
thanks again
steve
RE: hot running motor
Motor overload protection, simply the name suggest its purpose that is, to protect the motor from overloading.
Refer to NEC(National Electrical Code)for a minimum requirements for motor overload protection.
RE: hot running motor
Overload protection in YD setups
You say you have a 4kW motor, I guess approx 7.5Amps FLA
Overload protection can be applied to this setup in three ways:
a) If you have a motor protective breaker in the three phases upstream of the main contactor then you would set the overload of the device to FLA of the motor as stated on the motor plate.
2) If you have an overload after the main contactor then you would set the overload to 58% of the motor FLA as the delta current is 1/1.732 in one side of the motor feed. This gives partial protection of the motor when switched in star.
3) If you have the overload after the delta contactor then again it's 58% of the motor FLA. In this case the motor is not protected in star. This is quite uncommon and only really used in applications of long star > delta periods.
Regards
silva.foxx
RE: hot running motor
regards steve
RE: hot running motor
Lets not forget the obvious, check the cooling fan. Make sure its still a tight fit on the shaft and that the baldes are intact.
RE: hot running motor
The current unbalance is creating a small magnetic field but running backwards. That field reduces (brake) the effective shaft torque and it is producing heat, which is a reason for the increased temperature rise.
Current unbalance could only be the result of non symmetrical windings or unbalanced voltages. The reported currents average 4 amps and a maximum unbalance of 0.5/4*100= 12.5%. However, to produce this current unbalance only around 1.5% of voltage unbalance is required, say 374.7, 380, 385.7 volts. See STD NEMA MG1 part 14.
If the unbalance can not be corrected, this motor load should be reduced not to exceed 3.9 kW. This could be achieved reducing the overload current setup.
RE: hot running motor
steve