VFD Motors and H2O

fluidpower1 · Apr 8, 2008

Is it possible to operate a VFD Motor under water?

If possible, What, in simple terms would be involved?

The reason I ask is, There are a lot of inquiries on the Hydraulic Forums about Hydraulic Motor Drives for Boat Propellers. The Pump would be Engine driven and the Hydraulic Motors would be under water with Prop's attached.

The big problem is CONTAMINATION from the normal Mineral Oil which can be overcome by using Bio-Degradealble fluids. Usually the Bio-Degradeable fluids limit Pressure and Pump RPM's which requires larger pumps and motors so the cost is HIGH.

I designed some of these systems in my earlier days when little thought was give to Environmental concerns but have stayed away from them since.

dmroeder · Apr 8, 2008

AB had something at the automation fair in Chicago. I believe it was a powerflex, but I can't be sure.

It was in an acrylic enclosure where water is spraying on it (in strategic spots). Not sure if you could submerge it though.

allscott · Apr 8, 2008

Are you talking about having the motor under water or the VFD or both?

Stationmaster · Apr 8, 2008

I JUST watched a news article about an electric car that uses batteries, an inverter, and a three phase motor. The performance was remarkable! It outran a Porsche AND an Indy car. In theory, the inverter is the same thing as the output section of a VFD, the batteries provide the DC bus, and the microprocessor and output semiconductors generate the three-phase power used to run the motor.

http://www.wrightspeed.com/x1.html

Underwater three phase motors are very common as they are used in submersible pump applications. I installed a 75hp last month. I'd guess they could be adapted to run a jet drive or maybe even a prop.

With TWO of them we could differentiate the speeds for steering...........

I'm in.....when do we start?

: )

Stationmaster

fluidpower1 · Apr 8, 2008

"Are you talking about having the motor under water or the VFD or both?"

As far as understand VFD driven Motors,only the Motor is requires to be underwater sice it is driving a propellor to move the boat.

CowDung · Apr 8, 2008

Why does the motor have to be underwater? I would think that the use of a shaft to drive the prop would keep the motor dry. Gasoline engines aren't really underwater when they are used to propel a boat...

fluidpower1 · Apr 8, 2008

Some don't have to be under water but under water installation GREATLY SIMPLIIES all the installations I'm familiar with.

Others, such as Bow or Stern Thrusters are often mounted in Tubes that make an under water connection path from Left to Right of the boat and have the motors and propellers mounted in them to allow Sideway Movement when positioning the boat while docking. A local Sternwheeler Gambling Boat uses these thrusters to help get in back to its moorings in the river current.

There system uses Hydraulic Motors but I'm not sure how they get around oil leakage that will occur, sooner or later. I do know they use 25-35 PSI case pressure to keep water out of the motors and hydraulic circuit.

bikerdude · Apr 8, 2008

Hey,
Like the others have said, these motors are readily available for water well pump usage. We use Franklin Electric pumps & motors. They are located in Indiana which is a plus for us. See the picture. Just Google "Franklin ELectric" for their web site. No... I don't work for them, I just use their products.

Basically just need to insulate the motor leads in a water proof maner, we use special heat shrink tubing on splices & there is a special conduit fitting that seals the pump/motor housing from the outside world. We use a AB 1336-Plus VFD to drive the motor. I don't know where your going to get the electrical curent/voltage necessary to run one of these on a boat. Maybe a diesel generator?

BD

Steve Bailey · Apr 8, 2008

This is covered by the motor's IP (Ingress Protection) rating. It's a two-digit number that specifies the level of protection against solids and liquids. Motors on machine tools are quite often IP67 which sounds like what you're after. If the motor will be submerged at a depth of greater than 1 meter you'll need to go to IP68.

Type "IP67" into Google for details.

fluidpower1 · Apr 8, 2008

Thanks for the help. I believe your input will be interesting to posters on the Forums on Hydraulics. At least it should be.

leitmotif · Apr 9, 2008

fluidpower1 said:
Is it possible to operate a VFD Motor under water?

If possible, What, in simple terms would be involved?

The reason I ask is, There are a lot of inquiries on the Hydraulic Forums about Hydraulic Motor Drives for Boat Propellers. The Pump would be Engine driven and the Hydraulic Motors would be under water with Prop's attached.

The big problem is CONTAMINATION from the normal Mineral Oil which can be overcome by using Bio-Degradealble fluids. Usually the Bio-Degradeable fluids limit Pressure and Pump RPM's which requires larger pumps and motors so the cost is HIGH.

I designed some of these systems in my earlier days when little thought was give to Environmental concerns but have stayed away from them since.

Bud

US Navy submarines have what is called a Submersible Propulsion Motor 325 HP 450 3 phase. It resides outside the pressure hull flush to the trim plating (ballast tanks) Can be operated at full test depth (equivalent to several hundred PSI). Lowered on a hydraulic cylinder and then could be rotated. Great for docking to push boat sideways. Noisier than all get out though.

The advantage of using just a motor mounted in the water (ie exteriorer to hull) is you do not need a hull penetration for a shaft, no shaft packing, can rotate the motor if you want to direct the thrust, easier to mount a Kort nozzle, still need a hull penetration for the conductors though.
Dan Bentler

Rich1955 · Apr 9, 2008

How do pods work, do they have the motor in them? Thats the new thing now as aposed to prop shafts.

VFD Motors and H2O

fluidpower1

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dmroeder

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allscott

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Stationmaster

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fluidpower1

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CowDung

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fluidpower1

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bikerdude

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Steve Bailey

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fluidpower1

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leitmotif

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Rich1955

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