Maker Pro
Maker Pro

Re: Why Space Heater for Induction Motors

D

Don Kelly

Jan 1, 1970
0
----------------------------
Govind said:
Dear all,

Why a space heater is required for Industrial Induction Motors?

My ans. is to avoid condensation. ok. i agree.

If so Why space heaters are not provided for lower kW motors (say 1.5,
1.1 kW etc) . Why only for higher kW motors space heaters are provided
(say 132kw above). Even all motors are to be located at the same
Ambient Temperatures ( say 5 Deg to 45 Deg Max). For the same ambient
temperature at site, in my opinion all motors should have condensation
heaters. Could any body can please explain the philosophy behind the
basis of above ?..............

---Govind

--------------
Why should space heaters be required for any induction motors?

It seems to me that cooling is a more important consideration in most
situations.
The problem with condensation implies that the motor is cooler than the
(humid) ambient air around it. A somewhat unusual situation considering
that a motor is a heat source.
 
D

Don Kelly

Jan 1, 1970
0
Bill Shymanski said:
Years ago, I bought a couple of 500 HP weatherproof motors for a dust
collection system and ordered space heaters for them because they were
installed outdoors; I wanted them to stay dry if the motors were ever
shut off, especially in damp weather. Another gadget you can use
instead of a space heater is a winding heater that passes a few per cent
of rated current as DC through the winding when the motor is otherwise
de-energized; this heat keeps the windings warm.

I've seen space heaters as an option on smaller motors, too.

Bill

OK- that is a fair enough answer. However, the problem arises- is this a
necessary precaution considering that the motor temperature should be at
ambient or above? If condensation occurs, typically it is external so, is
this overcompensation for a problem that may not exist. Is this a typical
practice for (e.g.)oil well pump motors in Alberta- which as I recall are
"weatherproof"?

Don Kelly [email protected]
remove the X to answer
----------------------------
 
R

Rheilly Phoull

Jan 1, 1970
0
Don Kelly said:
OK- that is a fair enough answer. However, the problem arises- is this a
necessary precaution considering that the motor temperature should be at
ambient or above? If condensation occurs, typically it is external so, is
this overcompensation for a problem that may not exist. Is this a typical
practice for (e.g.)oil well pump motors in Alberta- which as I recall are
"weatherproof"?

Don Kelly [email protected]
remove the X to answer
My experience is that if the motor is located in a humid space and subjected
to changes in ambient temperature (All whilst not energised) the heaters are
a good precaution, particularly as the motor ages. An example would be an
outside 'weather proof' pump motor that would be cold overnight and warmed
by the sun. Also once again the problem of condensation arises if the unit
only gets random or occasional use like transfer pumps or sump pumps etc.
 
R

Rheilly Phoull

Jan 1, 1970
0
Govind said:
Hi all...,,,,,,,

I agree with all your answers i.e.,
1. Heaters are energised when motor is in idle - while not running
2. Even though motor is placed outdoor or indoor
3. Irrespective of Enclosure whether WP or TEFC etc
4. Not only in humid place - also for place where humid condition
expected to occur
5. I also agree with heating by means of winding itself by injecting
lower voltage of DC / AC

Please note my question that i need to have the basis to FIX A kW
rating of a motor i.e from what kW rating i have to provide space
heater???????????. Some Electrical consultants are providing space
heaters for motors of 75kW and above for a particular region for the
same region another consultant advising to provide space heater for
110kW and above rating. Why this controversy. what is the basis please
explain,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,

Govind
IMHO the use of heaters is governed by the duty and location of the motors
not by the voltage or KW.
As mentioned if the operating voltage is above medium then the heaters are
at least good insurance.
I think in practice the decisions are made by the design engineers, either
at the product end or the site.
 
D

Don Kelly

Jan 1, 1970
0
Bill Shymanski said:
Don't know what they do in the oil fields but my concern was that the WP
motor frame lets air freely circulate around the windings. My scenario
was a summer shutdown when the motor would be down for a couple of
weeks, taking in whatever dew and rain happens during that time, then
soaking the insulation and blowing up when powered up again. True, the
manufacturer did tell me that the windings were hipotted under water -
encapsulated. Maybe it was over compensation.

An almost entirely unrelated problem happened at the same plant some
years before. They found that motors left shut off during a -35 C cold
snap destroyed their bearings when restarted; the particular motors
shrank enough under the cold condition to damage the bearings. Changing
motor manufacturers was sufficient to solve the problem. But if you
plan on leaving a motor switched off for weeks in cold weather, it's
worth putting that into the specs.


Bill

Thanks Bill, Daestrom and Rheilly
You have all provided good and succinct answers.
 
Top