T-Pain Is On A Boat: Re: [Electric Boats] AC vs DC motors

Sunday, July 24, 2016

Re: [Electric Boats] AC vs DC motors

Your needs/wants are very similar to mine. I love gunk holing and inland rivers and canals so as much as I enjoy sailing as well the bulk of my needs are for power. I am looking for a very efficient platform to convert. The great loop is defiantly on my bucket list.

4 to 5 kn is not a problem for most of my needs bit I need the ability to double that in a pinch. There will be places where I need to go upstream and the flow itself is 4 or 5 knots.

I am currently looking out for an old 27 or 30 foot stilleto as a conversion platform. They are very light and I hope have enough reserve bouncy to handle some extra weight without becoming a complete dog. I'm wondering if anyone is familiar with these boats and would love some thoughts.

Nick

Sent from my Bell Samsung device over Canada's largest network.

-------- Original message --------
From: "David Adams lonzim.adams@gmail.com [electricboats]" <electricboats@yahoogroups.com>
Date: 2016-07-23 1:25 AM (GMT-05:00)
To: electricboats@yahoogroups.com
Subject: Re: [Electric Boats] AC vs DC motors

A bit more info.
I'm aware diesel electric will never be as efficient as direct diesel propulsion. But i feel the benefits of being able to run at slower speeds for 5 or so hours a day on solar power counteract the inefficiency. When moored or anchored, which will be a large percentage of the time. We won't need to run the generator. Even when on a long passage. The solar augmentation of power requirements for five or six hours a day should allow significant fuel savings. Even to the point where it counteracts the initial diesel electric inefficiency. I also think we would be able to run a much smaller battery bank because we're prepared to burn fuel when the need arises. Would appreciate your thoughts and comments. Dave.

On 23 Jul 2016 07:05, wrote:

Thanks for the response. I plan to power it with about 70kW of solar pv in conjunction with a large diesel generator. The idea is to install this in to a cruising boat. Run the generator when large power required. Eg ocean crossings. But run mostly on solar when cruising in amongst islands / coastal cruising etc. It's a huge project and I'm a few years off getting started. So at the moment all I'm trying to do is educate myself. All comments most welcome and thanks again. Dave.

On 21 Jul 2016 17:35, "Hannu Venermo gcode.fi@gmail.com [electricboats]" <electricboats@yahoogroups.com> wrote:

Em..
100 kW is extreme.
How to you plan to power them ?

A new VFD+3-phase is potentially == same efficiency as a AC brushless
servo, and internally they are similar.

In my experience, the ac brushless motors are more efficient, since
smaller motor deliver the same power and have lower noise and heat less.
But, thats at 2.5 kW, and upto 40 kW on VFD + 3-phase.

I don´t think efficiency numbers are commonly available in the bigger
ones- thus I don´t think there is a lot of data.
Peak efficiencies are about 92-93% for Tesla, who designed their own,
and have done 12 revisions of it in the last 10 years.

Thus, it is quite likely that all common cots stuff is quite a bit less
efficient.

The most efficient one I have seen with data was a recent post by a
member, with about 86% efficiency, on a setup I might think is typical,
but much smaller.
Peak efficiency was quoted as 92% for a given setup, in their range.

Thus, it seems You might get somewhere around 85-90%, most likely.

My VFD+phase motors vs AC brushless experiences - the AC brushless is
very much more efficient.
The AC is smaller, has more torque at low speed, reacts much faster,
generates less waste heat.

On 21/07/2016 11:11, David Adams lonzim.adams@gmail.com [electricboats]
wrote:
> Greetings all,
>
> I'm trying to learn the differences between powering a boat with AC vs
> DC Brushed vs DC Brushless motors.
> I'll need something in about the 100kW range.
>
> My initial thinking is to use AC as these motors are easily available
> but I have no idea of the differences in efficiency.
>
> Could someone point me to a resource where I can learn more about this
> please?
>
> Best regards
>
> Dave

--
-hanermo (cnc designs)