hot running motor 10

[steveholloway]

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

 

[waross]

The first thing to check is the voltages. Do you have a voltage imbalance?
yours

 

[stardelta]

4kw moving 80tonnes a min? thats over a tonne a sec` are you sure about those figures? Pump nameplates usualy quote quantity/time as opposed to weight/time using the Q/h nonclementure. Can you post the full nameplate details particularly rated current and voltage.

 

[LionelHutz]

What's "quite hot" mean? If you can't touch the motor that doesn't mean it's too hot.

 

[waross]

What is the name plate current of the 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

 

[steveholloway]

thank you gents i was imformed that it was 80 tonnes a min i guess that must be wrong i will double check the figures. by quite hot i meant that you could place your hand on the casing without burning yourself. at the moment the ambient temprature here in cyprus is around 32deg c i personally feel that this is probably the main reason for the hot running of the motor thanks again
steve

 

[powerjunx]

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.

 

[ScottyUK]

If you can put your hand on it the temperature is unlikely to exceed 70C, and at that temperature you would not keep your hand on it for long. In a 32C ambient the rise is nothing alarming.


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Sometimes I only open my mouth to swap feet...

 

[Skogsgurra]

Actually, 55 C is the limit. You can not hold your hand on a surface that is hotter than that. So your motor is, in fact, running very cool. At 32 C ambient and hot spot about 10 K above surface temperature, you have something like 55 + 10 = 65 C. No problem at all.

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

http://www.gke.org

 

[stardelta]

Skoggs?
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/

 

[electricpete]

I agree you need to verify whether it is really hotter than expected.

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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[stardelta]

Further to the above, European manufacturers dont generaly market and sell products in a country that are unsuitable for use in that particular country or meet its standards. Ok you can harmonise frame sises and supply voltages throught Europe but (unfortunately) not the weather! I doubt a well known and respected company such as Grundfos wont sell a pump-set in a country knowing its likely to overheat due to ambient conditions otherwise it becomes a warranty issue. However that doesnt stop an unknowing individual from obtaining and installing an unsuitable unit. Best talk to Grundfos themselves but have all the nameplate information to hand including accurate supply voltages and pipework/system details.

 

[waross]

Reality check;
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.

 

[Skogsgurra]

Yes YD, never seem to get them 'fosses' right.

Gunnar Englund

http://www.gke.org

 

[arcflash99]

I would check voltages also. If there is a voltage inbalance, verify the supply voltage if OK, you may have a bad connection. Perform infrared scan or at least scan the connections with a temperature gun.

NEMA Standards MG 1-14.35 indicates derating a motor's HP rating by 25% with a 5% voltage imbalance.

 

[steveholloway]

thanks once again gents, i havn't had much experience with motors until i came here to cyprus i guess i have a lot to learn it is a facinating subject.

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

 

[powerjunx]

steveholloway,
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.

 

[foxxy]

Hi Steve

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

 

[steveholloway]

thanks again guys i havn't had time to get back to the pump this week i will keep you posted

regards steve

 

[stardelta]

Steve?
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.