Prime Generator shut down at 110% load

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Sajid khan

Senior Member
Location
Pakistan
Hi,
We recently had invited by our vendor for the load testing of generator. The generator is 150kVA prime rated tested on load bank with unity power factor. The load test was going fine from no load to 100% load. We asked to test genset on 110% load i.e at 132kw. Since the generator is of prime rating it should withstand 110% load for one hour by the definition of prime rated generator set but, the generator get shut down due to temperature rise(107C) goes beyond temperature limit(96C).
The arrangement of generator was such that the load bank was placed near to the alternator side.
The technical team of the vendor give the justification for generator shutdown is due to hot air released by load bank sucked by alternator into the generator canopy causing temperature to rise beyond the threshold limit.

Is this the correct justification??

Is there any possibility of temperature rise due to unity power factor load bank??



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petersonra

Senior Member
Location
Northern illinois
Occupation
engineer
This is one reason why it is not unusual for larger alternators to have temperature measurement on the cooling air on both the inlet and outlet.

Now that you know that the thing tripped on high temperature, I would start doing some closer investigation as to just what ambient temperature it can operate at.
 

Sajid khan

Senior Member
Location
Pakistan
This is one reason why it is not unusual for larger alternators to have temperature measurement on the cooling air on both the inlet and outlet.

Now that you know that the thing tripped on high temperature, I would start doing some closer investigation as to just what ambient temperature it can operate at.

The maximum allowable ambient temperature as specified by manufacturer is 45C


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gadfly56

Senior Member
Location
New Jersey
Occupation
Professional Engineer, Fire & Life Safety
It should be readily apparent from the physical arrangement of the equipment if the vendor's argument is tenable. I'd suggest a simple digital recording thermometer be placed at the cooling air inlet and then re-run the test.
 

Besoeker3

Senior Member
Location
UK
Occupation
Retired Electrical Engineer
The arrangement of generator was such that the load bank was placed near to the alternator side.
Shouldn't the vendor, who presumably arranged the tests, know that the proximity of the load could result in such an outcome?
Sounds fishy to me.

I would ask the vendor to revise the physical arrangement such that heat from the load bank was distance from the alternator. If he can't, I would decline the sale on the basis that it does not meet the claimed specification.
 

gadfly56

Senior Member
Location
New Jersey
Occupation
Professional Engineer, Fire & Life Safety
Shouldn't the vendor, who presumably arranged the tests, know that the proximity of the load could result in such an outcome?
Sounds fishy to me.

I would ask the vendor to revise the physical arrangement such that heat from the load bank was distance from the alternator. If he can't, I would decline the sale on the basis that it does not meet the claimed specification.

I'd be surprised if the vendor was responsible for the equipment layout at the customer's site, unless hired for that purpose. They might even have a warning in their installation manual about having the cooling air intake too close to heat sources.
 

Hv&Lv

Senior Member
Location
-
Occupation
Engineer/Technician
I'd be surprised if the vendor was responsible for the equipment layout at the customer's site, unless hired for that purpose. They might even have a warning in their installation manual about having the cooling air intake too close to heat sources.

True, but the vendor should know his equipment enough to bring this possibility to light BEFORE the test starts.
 

gadfly56

Senior Member
Location
New Jersey
Occupation
Professional Engineer, Fire & Life Safety
Shouldn't the vendor, who presumably arranged the tests, know that the proximity of the load could result in such an outcome?
Sounds fishy to me.

I would ask the vendor to revise the physical arrangement such that heat from the load bank was distance from the alternator. If he can't, I would decline the sale on the basis that it does not meet the claimed specification.

I'd be surprised if the vendor was responsible for the equipment layout at the customer's site, unless hired for that purpose. They might even have a warning in their installation manual about having the cooling air intake too close to heat sources.
 

iceworm

Curmudgeon still using printed IEEE Color Books
Location
North of the 65 parallel
Occupation
EE (Field - as little design as possible)
Sajid -
I'm guessing this is a Factory Acceptance Test - at the factory/vendor.
The gen did not pass.

As gens go, this one is not that big. Cables are not so large the Load bank can't be located away from the gen. Suggest to add required instrumentation, relocate the loadbank, rerun the test.

The mfg/vendor has to meet spec.


Add one thing. What does the spec sheet say? Does it acknowledge the prime ratings? The gen has to meet spec. But only what is in the contract.
 

Sajid khan

Senior Member
Location
Pakistan
This is one reason why it is not unusual for larger alternators to have temperature measurement on the cooling air on both the inlet and outlet.

Now that you know that the thing tripped on high temperature, I would start doing some closer investigation as to just what ambient temperature it can operate at.

The ambient temperature as specified by the manufacturer is 45C.


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Sajid khan

Senior Member
Location
Pakistan
This is one reason why it is not unusual for larger alternators to have temperature measurement on the cooling air on both the inlet and outlet.

Now that you know that the thing tripped on high temperature, I would start doing some closer investigation as to just what ambient temperature it can operate at.

The ambient temperature as specified by the manufacturer is 45C.


Sent from my iPhone using Tapatalk
 

Sajid khan

Senior Member
Location
Pakistan
This is one reason why it is not unusual for larger alternators to have temperature measurement on the cooling air on both the inlet and outlet.

Now that you know that the thing tripped on high temperature, I would start doing some closer investigation as to just what ambient temperature it can operate at.

The ambient temperature as specified by the manufacturer is 45C.


Sent from my iPhone using Tapatalk
 

Sajid khan

Senior Member
Location
Pakistan
Sajid -
I'm guessing this is a Factory Acceptance Test - at the factory/vendor.
The gen did not pass.

As gens go, this one is not that big. Cables are not so large the Load bank can't be located away from the gen. Suggest to add required instrumentation, relocate the loadbank, rerun the test.

The mfg/vendor has to meet spec.


Add one thing. What does the spec sheet say? Does it acknowledge the prime ratings? The gen has to meet spec. But only what is in the contract.

Yes the specs says a prime rated genset.
I Checked the name plate and manufacturer specs sheet, its the same prime rated genset.


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Besoeker3

Senior Member
Location
UK
Occupation
Retired Electrical Engineer
I'd be surprised if the vendor was responsible for the equipment layout at the customer's site, unless hired for that purpose. They might even have a warning in their installation manual about having the cooling air intake too close to heat sources.

If the customer was invited by the vendor, I would have expected the tests to have been done at the vendor's site.
 

PaulMmn

Senior Member
Location
Union, KY, USA
Occupation
EIT - Engineer in Training, Lafayette College
If the customer was invited by the vendor, I would have expected the tests to have been done at the vendor's site.

If it's a demo/test at the vendor's site, most vendors will run the test before the customer arrives to make sure it works! Although they might not have tested the 110% load.
 

Sajid khan

Senior Member
Location
Pakistan
If it's a demo/test at the vendor's site, most vendors will run the test before the customer arrives to make sure it works! Although they might not have tested the 110% load.

Yes exactly they did-not test on 110% load.


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