200 KW MOTOR TEMP RISE IF AMBINET TEMP IS 50 C AND LOAD IS i. 86 % & ii. 100 % OF RATED CURRENT

Lets start with Home work first

Consider winding temp to be 20 ~ 40 C more than motor body temperature. We will consider it 30 C.

i. At ambient of 32 C, motor body temp is 76 C and motor winding temp will be 106 C ( 76 + 30 = 106 C )

ii. When ambient increases from 32 C to 50 C, motor body temp also increases i-e 76 + ( 50-32 ) = 94 C. Therefore motor winding temp becomes 124 C ( 94 + 30 = 124 C ).

It means at 50 C, motor winding temp will be 124 C at 86 % of its rated load.

iii. Since motor is running at 86 % of its rated load and when load is increased from 86 % to 100 % or 292 to 337 Amp, there will be 14 % increase in temp too ( It is assumption, unable to find any relation of winding temp to load ).

So at 100 %, winding temp would be 141.36 C or 142 C ( 14 % increase due to increase in current in winding ).

iv. Since insulation class of motor is F, so max operating temp of motor winding would be 145 ( 145 = 155 - 10 C for hot spot ).

Refer to para iii & iv, max operating temp is 145 C where as at 100 % load, motor will run at 142 C. So there is very little margin and motor insulation life is compromised.

The statement <...Load of the fan is almost constant...> is not plausible given it is an <...inverter duty induction motor driven by ...VFD [assume "variable frequency drive"]...>. Usually the load of a fan is proportional to about the cube of the tip speed, and the presence of the <...VFD...> suggests that the fan speed is far from <...almost constant...>.

The question <...Does motor withstand at 50 C ?...> is something that needs to be discussed directly with the motor manufacturer in the first instance. The forum is not able to do this. After all, the motor manufacturer's name, the motor part number and the manufacturer's telephone number have all been withheld from it.

The answer to the question <...What would be its body temp at 50 C [ambient]...> depends upon how it is cooled, which has been withheld from the forum.

If the <...motor body temp is 76 C...> then steps to prevent inadvertent contact with people should be taken so as to avoid injury.

Is there a serviceable spare motor available in case of catastrophic and irreversible failure of the installed one?

https://www.quantum-controls.co.uk/insights/faqs/how-do-i-classify-the-temperature-limits-of-an-electric-motor/#:~:text=Insulation%20classes%20B%2C%20F%20and,the%20risk%20of%20permanent%20damage.

Under what circumstances does <...ambient temp goes upto 50 C...>?

Thanks for interest . . .

Response to Reply # 4 :

System is deigned for ambient Max upto 50 C. In May, temp normally remains above 45 at day time between 1:00 PM to 3:00 PM.

Response to Reply # 3 :

Useful link

i. At 50 C, there will be 10 % reduction in Power rating of the equipment.

ii. For Insulation F, 145 C is the maximum temp to which insulation for a short period of time.

Response to Reply #2 :

Information demanded to be included or action to be taken doesn't contribute to the soul and spirit of question being asked in this forum.

i. Load is constant means this is Max load at normal operation. If here we start discussing affinity laws, actual issue will be lost.

ii. Motor manufacturer or designer are doing business. To them everything is fine until proven to be wrong.

iii. Motor has its own forced cooling fan and info is already provided " Motor has its separate cooling fan i-e motor cooling is not related to motor speed or frequency " .

iv. Serviceable or spare motor : First rule in maintenance field is to keep critical spares in inventory to avoid bad days.

In industry, related to motor winding temp, at 110 C there is alarm and at 120 C, motor is tripped. These are very safe and secure limits.

Many Electrical machines designed formulas couldn't be applied because motor is not operating at 100 % load and many parameters from motor supplier are missing i-e thermal curves, heating and cooling time constant, load vs temp rise curves etc.

I'm concerned that your motor presents a body temperature that is 44° C above the ambient room temperature of 32° C and has type F insulation windings. Why did the manufacturer use such a high-temperature winding? Probably because this motor already runs hot at room temperature. If they chose such hot winding insulation so it could work in higher ambient temperatures they would probably advertise this on the nameplate.

Contact the motor manufacturer.

Class F insulation is practically a standard for mill and industrial duty motors, it would be supplied on any and all motor designs that were integral horsepower severe duty machines in mill and chemical applications, usually totally enclosed fan cooled. The ubiquitous 1.15 service factor is often a result of operating class F insulation at a class B temperature rise, the 1.15 service factor is operating the same machine at the Class F temperature rise. Nothing special.

400V 50Hz and kW rating means this is annIEC motor where “Service Factor” does not exist.

Not necessarily, but it would have been a good point to establish, the design basis for the machine. I believe the OP said it was designed by ABB, which was the only information needed to find out how it would perform under non-design conditions.

Your posts suggest the presence of a thermal sensor that will open the control circuit when it is too hot.

Does your motor have an embedded temperature sensor in the motor's windings so the drive can read the actual temperature of the motor during operation? If you do have an embedded temperature sensor you could program the drive to reduce the speed of the fan to limit the motor's temperature rise when needed. This would probably require a change in process conditions, which may or may not be possible. Since you mention limited hours of exposure to high ambient temperature, this may be possible.

If you can't read the motor's winding temperature directly, you could mount a temperature sensor on the motor's frame, or even better, put it in the exhaust air stream from the cooling fan's flow through the motor. You could compare this temperature reading to the numbers suggested from post #1 and get a reasonable approximation of actual winding temperature.

Is the motor protected from direct heating from the sunlight or nearby heat sources? If not, do so with a reflective barrier or shade or similar method.

All of this is ignoring the topic of climate change and future exposure to substantially higher ambient temperatures.

--JMM

Thermister is not available in motor winding. Temperature of motor is taken via Infra red temp gun.Motor winding temp is normally 20 ~ 40 C higher than motor body temperature. Therefore winding temperatures are not accurate one but assumed one. i-e

Winding Temp = Motor body Temp + 30 C.

Motor is installed under shed. Basically motor is running at 85 % of its rated Torque and Current. At such load, temp rise is normal but when compared with 45 ~ 50 C of ambient , it seems that this motor wouldn't work and fail.

Temperature difference between motor air slots and bearing housing is 7 C. When ever motor body temp reaches to 90 C, bearing housing temp would be 82 which is threshold. Above this temp, bearing may fail.

If the <...bearing may fail...> then the motor may not survive the event, in which case its temperature is irrelevant

How did the discussion with the motor manufacturer go?

Motor body temperature is not used in the application of motors in my 40+ years of industrial mill & chemical application experience. The design has been predicated on a given ambient temperature, which has been standardized to be 40C and assumes 100% duty cycle, which includes a typical 1.15 SF in many cases. The motor is designed to operate continuously under those conditions, with some expected service life at the 1.15 service factor, in that ambient. I have never lost a motor applied within those parameters except when reset many times due to overload, improperly sized overloads, or paper pulp covering more than 50% of the fan openings. This includes winding and bearing failures. So if you have a properly designed motor installation, just be concerned with knowing your ambient air temperature, and your load.

A rule of thumb about surface temperature, if you touch the motor and it’s so hot you involuntarily move your hand, check the load. A fully loaded motor will be so hot you can touch it, but cannot keep your fingers on it except momentarily.

The motor was designed to remove the heat in the windings by running hotter than the air passing across the body. Only the designer knows what a particular design body temperature was, and how that temperature is distributed around the motor body. If you are not the motor designer, measuring surface temperature is a waste of time except in relative terms for the same application, perhaps. Motor amperes is the more reliable measure.

The only way to get reliable information on operating in a higher ambient temperature is to contact the designer of the actual motor you are inquiring about, or to measure your embedded winding temperature sensors. Or you can guess, like we are doing here, and wait and see.

Assumed winding hot spot temperature rises have been measured and verified extensively for transformers, oil temperature to winding temperature. I have not seen any work published for induction integral horsepower motors, so I would ask for a citation if using that sort of non-specific information. It sounds logical, but is definitely NOT the same thing.

Operating the motor with a non-sinusoidal power supply compounds your application complexity, as people have been finding out in the past 20-30 years. The extra heat developed in the laminations has led to motor design changes and ratings specifically for this type of power supply. The body of general knowledge for this scenario is very very young, by industry standards. Again, only the actual motor designer can give you the information you seek.

According to NEMA MG 1 MOTORS AND GENERATORS 12.43 TEMPERATURE RISE FOR MEDIUM SINGLE -PHASE AND POLYPHASE INDUCTION MOTORS, if the ambient temperature is above 40oC then the permitted motor temperature rise has to be derated with the difference from actual temperature and 40oC.

Let's say the motor insulation it is class F of 105 degrees permitted rise for 40oC ambient. Then the new permitted rise will be 95oC.

Since the temperature-for a limited difference-it is direct proportional with the losses then the new total losses have to be reduced with 95/105 factor.

The losses are divided in two parts: one constant and one variable.

The constant part may be Magnetic Core Losses, Friction and Windage Losses and Stray Load Losses. This may be 40-45% of total losses.

The copper losses-in stator and in rotor-depend on current level.

If the total losses have to be 95/105 for 50 degrees ambient [90.5%],that means the variable part- depending directly on current- has to be 90.5%-45%=45.5%

The current now will be about √(45.5/55)=0.91% of the rated.

ABB recommends to reduce about 7-10% of the rated load for 50oC ambient.

Yes, GA. Presumably, the mechanical load this fan will impart on the motor will be relatively constant for easy calculation.

I find the motor's power sizing to be a little odd though. 200 Kw is a lot of power for a fan. That sounds more like a traction motor for a vehicle.

As an example, the Induced Draft Fan on a kind of small chemical recovery boiler in upstate NY is an 1100kW rating. This might be a Force Draft Fan on a smaller boiler. Industrial building air handler for a 300’ x 50’ x 35’ building was 93kW, so getting up there.