About a year ago there was a fair bit of discussion on here about this, as I was looking at using one or two to power a canal narrowboat on an environmentally sensitive stretch of water. BLDC motors come in two main types, brushless permanent magnet motors, which often come from China as they mine the rare-earth minerals that are used in the very high field-strength magnets in these, and switched-reluctance motors which don't use permanent magnets, but have to be larger for the same power.
There are also permanent magnet ac motors (PMAC) which are very similar to brushless permanent magnet motors, but drive the multiphase field coils in a different manner. There's lots of data on the web, but you need to have a good understanding of electric motor principles to understand all of the advantages and disadvantages of the various types.
One advantage of all of these types is that they can be made of a large diameter with multiple pole pieces, so they can directly drive a propellor in an efficient way without needing a reduction gearbox. In some cases they are built into the cowl around the propellor itself.
They all need special dedicated control and drive circuitry. You can't just connect a battery to them and expect them to spin!
Chris Morriss.
On 17/12/2013 3:03 PM, Chris Moss wrote:
There are also permanent magnet ac motors (PMAC) which are very similar to brushless permanent magnet motors, but drive the multiphase field coils in a different manner. There's lots of data on the web, but you need to have a good understanding of electric motor principles to understand all of the advantages and disadvantages of the various types.
One advantage of all of these types is that they can be made of a large diameter with multiple pole pieces, so they can directly drive a propellor in an efficient way without needing a reduction gearbox. In some cases they are built into the cowl around the propellor itself.
They all need special dedicated control and drive circuitry. You can't just connect a battery to them and expect them to spin!
Chris Morriss.
On 17/12/2013 3:03 PM, Chris Moss wrote:
I've been reading Charles Mathys' book - Electrical Propulsion for boats (2004). He makes a big case for AC motors but an electrician doing work on our house suggested BLDC. Mathys doesn't appear to believe these are available for boat power levels, but when I googled "5kW BLDC motor" I got plenty of hits and it seems the way to go as they are more efficient than conventional DC and have fewer sparking issues. A useful explanation is here.
Now what I have to do is to find a reliable supplier in or closer to the UK. There are plenty on offer from the far east but I'd like some assurance of reliability and support if they misbehave. Does anyone have any thoughts?
One comment I've seen suggests they may be a bit noisier than other designs. Is this an issue?
Chris
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