Don't know the best...

http://www.raemotors.com/

Amps are meaningless without also knowing volts.

A permanent magnet motor is a DC motor and I would do my best to make sure it is an AC motor. Less maintenance, more uptime.

Your units and job description makes absolutely no sense. They demonstrate that you have no idea what it will take for this dream to become a reality. As an example, what do you mean by "an alternative energy system"? Will this energy source be a wind mill, a solar array, bio-fuel from the algae produced with your koi, a tread mill that you'll be doing your daily exercise with as you stare at your little fishies? I suspect that your 20 ampere rating is actually the circuit breaker rating for an existing system and not anything to do with the power you actually use.

Hire somebody or go back to school. You'll get no free engineering from me.

Your request is genuine, whereas our friends take it as a joke.

Permanent magnet motors for DC applications are very good, since they keep on working irrespective of the voltage delivered. They are ideal for Solar energy applications, where the voltage derived is very variable.

I have seen some motors made in Mexico, of just one horse power, being used for this purpose. They were quite robust, but that was more than 25 years back. You may ask some of the renewable energy people about it and also forward me that info, as I am also interested in securing reliable permanent magnet motors.

Gadepalli Subrahmanyam

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I'll try to be a bit more gentle than some others have been. The important quantity for a particular job is power (Watts or kW), not current. 20 Amps could be 120 Watts, if your system runs on 6V, or it could be 4800Watts, if your system runs on 240V. That's a huge difference.

It is not at all clear what it means to 'run a koi pond'. In some locations, all that would be required would be an aeration pump, which could be as low as 50 Watts. In most cases, a circulation pump would be desirable. The power required could vary immensely, depending on the size of the pond, desired flow rate, and change in elevation (if there is a stream and/or waterfall feeding into the pond).

Is any lighting involved? We don't know where you are located. In cold climates, the pond would have to be heated. Again, depending on the size of the pond, we could be talking about a few tens of Watts or tens of kW!

Give us MUCH more detail, and you will be MUCH more likely to get a useful answer...

Dear Friend,

There are many manufacturers and many models available in the market; from car wiper motors/ window closers to submersible pump motors. Best example is Cell phone vibration motor and these motors are very efficient. If you want to pump application then this type of motors are very costly (Submersible pump Rs.165000/- for 3 HP). I have converted a simple VFD that use solar electrical energy to run existing 3 HP submersible pump with above 95% efficiency.

Such motors are very expensive as suggested by Mr.Subermainum. You have not specified tech specs such as electric supply, detailed application, h.p required, duty cycle etc. You can contact Bharat Bijlee Ltd. on their web site www.bharatbijlee.com. for offer.

A 12V DC motor at 20 amps is 240 watts -- about the equivalent of one person power.

A 48 V DC motor at 20 amps is 960 watts -- a little more than one horsepower.

A 500 V DC motor (not uncommon in industry) at 20 amps is 10,000 watts -- about 13 horsepower.

Different manufacturers tend to specialize in different motor sizes and applications, so there is no "best DC motor" or "best DC motor brand". As someone else recommended, if you are just moving water around, then a bilge pump could be a good bet. These can be $30 - $75 or so (integrated motor and pump). A good DC motor for industrial purposes can be $100, $500, $50,000 - it all depends upon what you want to do with it and how critical the mission is.

You will need to specify what the application is, how much power you think you need to do the work, how many motors you need, the available voltage, etc.

Check with EDMOND SCIENTIFIC. They are pretty good with a variety of motors.