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blackrose

Permanent magnet technology

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Apologies if this has been posted before.

 

Apart from wrapping the motor around the prop which eliminates linkages and probably makes it more efficient, I'm not sure I understand the difference between this and an ordinary motor? Don't all motors have permanent magnets?

 

 

Edited by blackrose

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Most large motors don't have permanent magnets, they have two sets of electromagnets, with the moving set powered either by slip-rings or magnetic induction. Until relatively recently, sufficiently powerful and durable permanent magnets were not available.

 

MP.

 

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8 minutes ago, MoominPapa said:

Most large motors don't have permanent magnets, they have two sets of electromagnets, with the moving set powered either by slip-rings or magnetic induction. Until relatively recently, sufficiently powerful and durable permanent magnets were not available.

 

MP.

 

Also a dc motor works well with permanent magnets, whereas an ac ‘squirrel cage’ motor works by a completely different principle and can not use permanent magnets.  

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1 hour ago, blackrose said:

I wonder if this is the future of inboard electric motors? Peterboat will want one!

I have one on the bathtub! Google Cedric Lynch and his DC prime earth electric motors clever guy, He is setting up a 70 x 13 widebeam with two of them for drive on the Thames today

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Permanent magnet Dc motors have been in industrial use for many years, powered by a DC drive the speed can be adjusted to suit the application. 

Induction motors, or ‘squirrel cage induction motors, do not have magnets, but derive the magnetic force from an AC, Alternating Current, supply usually 3 phase 400Volt, they are relatively low cost, low maintenance, and rugged devices for industrial applications. For variable speed, inverter drive systems provide direction and variable speed.

The Rolls Royce device in the video will have ‘rare earth’ magnets, and very close tolerance manufacturing will produce high power, and high efficiency. The motor will have an electronic power drive for speed control, using embedded sensors in the ‘stator’ for monitoring and speed control. The design allows the motor package to be at the propellor as part of a swivelling pod, a system used for large vessels and oil rig’s essential for stability in high seas.

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1 hour ago, Tractor said:

Permanent magnet Dc motors have been in industrial use for many years, powered by a DC drive the speed can be adjusted to suit the application. 

Induction motors, or ‘squirrel cage induction motors, do not have magnets, but derive the magnetic force from an AC, Alternating Current, supply usually 3 phase 400Volt, they are relatively low cost, low maintenance, and rugged devices for industrial applications. For variable speed, inverter drive systems provide direction and variable speed.

The Rolls Royce device in the video will have ‘rare earth’ magnets, and very close tolerance manufacturing will produce high power, and high efficiency. The motor will have an electronic power drive for speed control, using embedded sensors in the ‘stator’ for monitoring and speed control. The design allows the motor package to be at the propellor as part of a swivelling pod, a system used for large vessels and oil rig’s essential for stability in high seas.

And will have Rolls Royce pricing...

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This type of propulsion is more suited to high accuracy industrial applications, where a return on a large investment can be made.

Not for Narrowboat propulsion perhaps, but for a dive boat with a bell suspended beneath at many metres depth; here these systems earn their keep by giving millimetre accuracy in large North Sea swells.

Industrial electric motors, well tried in small boats, provide a quiet, infinitely variable speed control, do away with the need for gearboxes; but the need for energy is always present. A tank of diesel, or a stack of battery stored energy, each display some volatility, and damage to the environment.

Getting into dangerous waters now, these are just my impressions.

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3 hours ago, Tractor said:

This type of propulsion is more suited to high accuracy industrial applications, where a return on a large investment can be made.

Not for Narrowboat propulsion perhaps, but for a dive boat with a bell suspended beneath at many metres depth; here these systems earn their keep by giving millimetre accuracy in large North Sea swells.

Industrial electric motors, well tried in small boats, provide a quiet, infinitely variable speed control, do away with the need for gearboxes; but the need for energy is always present. A tank of diesel, or a stack of battery stored energy, each display some volatility, and damage to the environment.

Getting into dangerous waters now, these are just my impressions.

I have 2 electric boats one has a lynch motor which is a very clever motor the other has an ex forklift motor it's a DC series, it's designed for 48 volts but is happy to run at 72 volts, I like the control ability of it and the instant massive torque it can deliver.  I am just looking at variable pitch propellers to get the best from it, no doubt they will be expensive but the write ups I have read are very positive 

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