Condensation Problem in Motor

Power would be E times I per winding, and you should be able to do some experimenting to determine the heat needed to overcome the rooms cooling. Id start with something like 10 amps and measure the resulting heating to see if it offsets the chilling. It sounds like your humidity in that room may be another problem to address, possibly more ventilation is needed. Woody

Another option would be using infra red lamps about the motor, connected through a spare auxilliary n/c contact of the staring device. It eliminates the need for dc power. And of course, as waldig suggested, better ventilation.

Why not install dehumidifiers to lower the moisture level prior to, and during shutdown? This would at least make the drying process faster...

One of the things I have seen done to achieve what it is you need to achieve is the placing of rod or strip heaters against the outside of the stator. Heat is heat... whether generated on the outside that radiates into the case or from the inside, both methods should work.

As a benefit, by this method, you do not make any electrical connections to the windings and... control of the heater elements at the lower voltage is much easier.

A dehumidifier may be the answer. Have one where all the heat from it is dry, direct that into the motor's cooling intake. Drain the condensate away from the motor room.

Some air conditioners use condensate to cool the condenser coils, eject a moist heat. You don't want that type. Split-types separate the two functions, all the water can be drained away, and all the heat goes to heat the motor.

WINDING DRY OUT USING HIGH CURRENT SUPPLY

To dry out of stator winding for Large Motor or generator and Wound Rotor, High current with low voltage injection to the winding is the best solution when baking oven is not available or not possible to keep inside due to limitation the baking oven dimension.

Supply the winding by dc current in approximately 60 - 70 % from FLA and keep the temperature round +/- (max) 80 to 90 degrees Celsius for at least 12-16 hours, depend on the winding insulation capacitance and condition "how much winding wet due to moist absorption"

Connect the winding in 1 phase, when the winding is 3 phases with 3 lead cable (wye or delta connection), connect the 2 phases in one (let say Phase U & V, to be connect together), and connect the current supply to phase W to U-V.

To avoid imbalance heat distribution in the winding due to imbalance Resistance between phase W and phase U-V, change the connection between phases, ie:

1st dry out, phase W to U-V

2^nd dry out, phase V to U-W

3^rd dry out, phase U to V-W

If stator lead are 6 cables, connect the 3 phases (U,V,W) in one phase, and power supply to be connected to phase to neutral (x,y,z)

OP says the motors are only off for a few hours, then presumably they want to use them again. Hooking up a bunch of DC wiring between runs may be troublesome.

A: Shoot the engineer that located the motors in such a place.

B: Build a vapor tight enclosure for the motors, with humidity control. A tight structure should not cost that much.

I think that for some reason, water trapped inside motor body, cycles between phases. What I can not understand is why you don't heat it and at the same time give water a path to get out (possibly help it by vacuum or silica) and then seal all the possible ways it would get back in. Even cabling route should not be ruled out. No way just atmosphere humidity would give isolation problems on a decent motor installation overnight. S.M.

One caution against using DC to warm the windings is that you might magnetically polarize the stator and rotor poles over time, leading to saturation when the motor is run on AC again. I once worked at an aluminum smelter where transformer-based arc welders were sometimes left in the potline room for long periods of time. The strong DC magnetic field of the potline would eventually magnetize the welder's iron core, rendering it unusable. When powered with AC, they would draw excessive current with every half-cycle because the core was magnetized in that direction, saturating at every other peak of the AC sine wave.

If something like this were to happen to your 11kv motor, it would ruin the motor!

For this reason alone, I would elect to use low-voltage AC (rather than DC) to warm the windings. The motor will be in a locked-rotor condition when warming, so there's no counter-EMF to contend with, meaning modest AC voltages should be all that are necessary to provide enough current to keep the stator warm and dry.

ventilation might sovle the problem. try intalling a fan blade directly to the armature shaft. it might work if the motor runs continuously or short cycles. direct ventilation to the outside of the building in tandem with the armature fan should definately solve the problem.

We have employed dehumidifiers to eliminate condensation in the store and to keep packaging materials from getting wet. This is less hazardous. It reduces down time. You may instal a localized humidifier and if your gadget is big enough, the whole enclosure could be dehumidified.

Spray it with WD40.

It works on wet spark plugs, leads and coils in car ignition systems.

Has the task of lagging the pipes and tanks been completed? If not, then there is a process cooling load somewhere else just waiting to be saved....

I agree with one poster who suggested that the humidity in the room needs to be addressed. An exhaust fan for the room may help.

However, IMO, you should not get condensation after only an hour even if the room humidity is quite high. The residual heat in the coils from running should not cool for several hours. I suspect something else is going on. My problem with condensation (vehicles stored in an unheated building) is when the temperature is rising and the humidity is high; this causes condensation on the cold metal when it doesn't warm up as fast as the room temperature. You should NOT get condensation, because the motors are warmer, plus the room temperature doesn't vary that much.

Exactly. That's why I suspected that water for some reason is already inside, and motor body can keep water from getting out equally well as from getting in. By the way, it should be obvious, but my phrase: water "cycles between phases" is about "water phases", not... electric phases. Hell, there goes a writer career. S.M.

Please make the motor installation place well ventilated. Also you may install several 400watt sodium vapor lamps just over the installed motor and the lamps will be in burning condition when the motor is not in operation. The heat generated by the lamps will keep the motor body in warm conditon and may prevent water condensation due fall of motor body temperature when not in operation. But before doing this, action should be taken to remove all entrapped moisture from the motor.

Also please check if there is any gap in the motor body, specially, in the terminal box,cable termination, etc, to prevent entry of the outside moistures.

Thanks,

Manindra