Difference between Dry motor and wet motor 1

[m15]

Hi All,

I like to know the difference between Dry motor and wet motor can any 1 explain.

 

[wetwind]

M 15,

The wet wound motors I'm familiar with are for boiler water circulating pumps and submersible water supply pumps. Wet wind motors have a fluid (the fluid the unit is pumping) in the gap between rotor and stator and surrounding the conductors in the stator slots. The magnetic gap tends to be a bit larger the conventional motors and they use hydrodynamic journal bearings which are also lubricated by the pumping fluid. The conductors are covered with a thicker insulation (Cross linked poly-ethylene) and use a random wind (conductors are pulled through the stator slots one at a time and the end turns and individually formed). A heat exchanger is used to supply cooling water to the wind and bearings as they are susceptible to heat damage. I hope this helps.

 

[itsmoked]

Would define a semi-hermetic refrigeration compressor to be a wet ynd motor? The refrigerant GAS runs thru the motor.

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com

 

[jraef]

Interesting point Keith. I would think so.

JRaef.com
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[mc5w]

Submersible well pump motors usually have nontoxic oil inside of the motor and a method to keep internal and external pressure equalized.

The smaller canned rotor pumps on forced hlt water heating systems have a paramagnetic wall between the rotor and stator that allows the rotor to live in the circulating water and uses water cooled bearings. The stator winding operates dry. The water circulation between the pumping chamber and the rotor is restricted to just enough to lubricate the bearings so that passive air cooling is enough to keep the bearings and stator cool enough. The lamination varnish of the rotor needs to be rated for a highly elevated temperature which is just another materials science problem.

Mike Cole

 

[jraef]

Submersible well pump motors usually have nontoxic oil inside of the motor and a method to keep internal and external pressure equalized.

Not necessarilly. Many deep well water pumps such as Hitachi / Sun-Star Electric's allow the water to flow through the gap.

http://www.sunstarusa.com/products/hitachi.html

JRaef.com
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[mc5w]

The last time that I changed out a submersible well pump was back in 1987. Evidentally, the technology has improved enough to allow water inside of the motor.

 

[waross]

I am wondering what the terms "dry" and "wet" refer to.
An open drip proof motor could be considered dry and a weather-proof motor considered wet.
Are we talking about the whole motor being externally wet, or are we discussing the various types of motors with the rotors and/or windings wetted by the process fluid or some other fluid?
respectfully

 

[stardelta]

Although fully oil-filled submersible motors exist I dont think it safe to assume that all submersible pump motors have oil filled windings. In some cases the oil is there only to provide cooling and lubrication for the mechanical seals. The majority of non bore-hole type sub`pumps and agitators made by names such as Flygt and ABS follow this design with cooling taken care of by the surrounding water. Some models feature moisture detection devices and float-switches that will isolate the supply should water enter the stator.

http://www.flygt.co.uk/14174.asp

No-one has yet mentioned roller motors. These machines are oil filled with the oil being shared between the winding and gearbox providing both cooling and lubrication.

http://www.interroll.com/en/drives_and_rollers/drummotors/

 

[jraef]

It would be nice if m15 responded to indicate the context of his question...

It doesn't appear he is a student posting to get an answer on a homework problem, so hopefully he will grace us with more information so we can sleep at night.

JRaef.com
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[m15]

Thanks for u comments.

In most of the cases we can see submersible pumps uses wet motors, but there are some companies manufacture both wet and dry motors submersible pump.wht is the merits and demerits between them.if 1 performs quite well than the other what is the necessity 2 manufacture the other 1.

pls advise.

 

[jraef]

With submersible pumps using what you are referring to as "wet" motors, a high level of particulate matter in the water (for instance sand) can rapidly wear away the winding insulation materials. For those places you would want to use a sealed pump that does not move the fluid being pumped through the motor itself.

JRaef.com
"Engineers like to solve problems. If there are no problems handily available, they will create their own problems." Scott Adams
For the best use of Eng-Tips, please click here -> faq731-376

 

[m15]

In Submersible pump, Dry motors are hermetically sealed with a high dielectric oil to exclude water from the motor. Wet motors are water filled motors for cooling.Like to know application wise how these motors differs.

 

[thewellguy]

With a water filled submersible well pump motor the water does not flow throught the motor. The motor comes from the manufacturer (Franklin electrice, Grundfos, Centerpro, Hitachi) filled with food grade alchol. There is a machanical seal around the output shaft the keeps the well water sperated from the fluid in the motor. If that seal fails the motor will still run becasue the winding are either made with jacketed wire or poured in epoxy.

With an oil filled well pump motor the winding wire is not insulted. The motor is filled with oil and The seal at the ouput shaft protects the winds. The seal can be mercy(Byron Jackson) or mechanical (Sun-star, Byron Jackson, Reda and others).
All the motors are "sealed" It more a matter of what will happen when the seal fails. Water filled motors can keep running and oil filled well ppump motors short out. However, both types of motor have there benifits.

 

[m15]

When i came across the dry motor submersible pump the motor has a limitation that it cant be used above 20m.whereas the wet motor submersible pump can be used till 350m.can i know why?pls advice.

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