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Evaluation of Variable Frequency Drive - water cooled versus Air cooled

Evaluation of Variable Frequency Drive - water cooled versus Air cooled

(OP)
Can someone share your views on water cooled versus Air cooled Variable Frequency Drive (VFD)?
The rating of the motor is 5.8MW.
The pros and cons of the above.

RE: Evaluation of Variable Frequency Drive - water cooled versus Air cooled

Water cooled will be more problematic but more flexible.

Keith Cress
kcress - http://www.flaminsystems.com

RE: Evaluation of Variable Frequency Drive - water cooled versus Air cooled

I 'own' several of both types.

The water-cooled are Siemens GM-150, two 9,000 HP, one 7,000 HP. Aside from some horrendous problems - five blowups in the first three years of service - at the beginning, they are doing quite well. The cooling water was a problem until the local owners got a handle on caring for the de-ionized water, including purchase of their own deionization equipment. The flow switches are little paddle things. We've had a couple of failures on the drive we run almost full time. We ran into problems during a particularly hot summer when the outdoor ambient air was too hot to adequately cool the drive's coolant supply.

I have ten Toshiba T300 MVi air-cooled drives in the 3500 - 6000 horsepower range, although the six 6000 HP units have yet to run under load due to the pipeline they servicer being held up by protests in the Dakotas.

The Toshibas that ARE in service have been trouble-free after a year. Due to the questionable situation with ambient air temperatures, we have 90 - 120 tons of air conditioning in the switchgear rooms where these drives are located. The drives themselves are cooled by this climate-controlled air.

I'm rather happy that the diagnostics on one of our drives detected an incipient winding failure of its motor and refused to start. The motor was tested by various means including insulation resistance, DC winding resistance, and the PdMA analyzer, none of which showed a particularly BAD motor. Toshiba checked their drive out and declared it good. We pulled the motor and when it was disassembled at a motor shop, the damage to the end turns was visible.

old field guy

RE: Evaluation of Variable Frequency Drive - water cooled versus Air cooled

It seems Toshiba should patent and commercialize their superior motor testing technology.

RE: Evaluation of Variable Frequency Drive - water cooled versus Air cooled

There are so many things that can go wrong with water cooled units. But if there's cool water available, they have one big advantage - no need for air cooling equipment with its high cost both for procurement and operation. We have cool air and cool water en masse but still some water cooled units. If they survive their first years and the heat sinks don't corrode (water chemistry important) they run for decades. Heat exchangers with large external cooling surfaces avoid many water problems (circulating water) and reasonable demand for cool air. Worked with such inverters in hot countries.

Gunnar Englund
www.gke.org
--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.

RE: Evaluation of Variable Frequency Drive - water cooled versus Air cooled

Liquid cooled large drives are typically smaller (footprint) than air cooled, as long as you pay no attention to needing a heat exchanger mounted somewhere else. In some areas, such as classified ones, that is not possible (I have that going on a a refinery right now), so air cooled is the only option. But when you get to 4000HP and above, the air volume gets extreme as well and A/C units become another point of failure, so you might end up needing redundancy. It's a complex web of details that must be explored and navigated.


"You measure the size of the accomplishment by the obstacles you had to overcome to reach your goals" -- Booker T. Washington

RE: Evaluation of Variable Frequency Drive - water cooled versus Air cooled

(OP)
Thanks for your feedback. Your experience has value to me.

If the air cooling has to happen at 54 deg C ambient air (in the tropical country) and the equipment is located in the middle of the operating refinery, then what which is better?
In my view water cooling should need less space and less noisy. Air cooling at 54 deg C ambient air may be less efficient. Hence larger cooling equipment may be required.

Once the cooling circuit water leakage is taken care, water cooled should be perfectly fine. Less noisy also. One should be careful with equipments used in the cooling water circuit.

Any view?

RE: Evaluation of Variable Frequency Drive - water cooled versus Air cooled

Most drives are designed to run at 40 C ambient. So it will be problematic to run with "natural" air. Air conditioning will be needed.

On the other hand, it is possible to oversize the power handling parts so the drive can operate at elevated ambient temperatures, like 60 C. You need even more air flowing but may be able to avoid cooling the air and that could translate into total lower cost and definitely less equipment to worry about.

Most drive manufacturers should be able to guide you to the right decision. There is a huge difference in "customer satisfaction" in a project like this and it is in everyone's interest to get it right. And that includes the supplier to a large extent. Talk to at least two of them and get their views. Or three, is better.

Gunnar Englund
www.gke.org
--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.

RE: Evaluation of Variable Frequency Drive - water cooled versus Air cooled

(OP)
Any one has experience in this regard in the region of middle east?
Please share your experience.

RE: Evaluation of Variable Frequency Drive - water cooled versus Air cooled

2
Howdy OldFieldGuy,
I too have installed many T300 MVi ASDs up to 7000hp, and you are 1000% correct in that cooling is a big deal. Fortunately (here in Canada) the outside ambient air is usually cool enough to ventilate the crap out of the ASD room (ie up to 60,0000cfm), without having to resort to AC.
I have successfully used Air-Handler Units (AHU)in drive rooms with up to 9000hp and outside ambient temperatures of -40C to +32C.
Most people are not aware that AC does not work well, or at all, in cold weather. So even though it may be -30C outside you still are required to get rid of 100's of kW's of heat from the drive room to the outside. An AC unit will not do that, you need an AHU.

I have never had to resort to water-cooled drives. I'm confident that they can be done properly, but I have only heard of horror stories.

I believe that the trick to successfully providing a reliable cooling system is too avoid the cheap-and-nasty commercial (AC &/or AHU) packages.
GG

"I have not failed. I've just found 10,000 ways that won't work." Thomas Alva Edison (1847-1931)

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