Electric Boar Prop Question

[seajayare]

On my boat I have 2x 6kW electric pod drives.(like a saildrive with the motor direct onto the prop). I usually use much less than 6kW so I can choose to run one motor at up to 6kW or both motors at 1/2 the the load each.

I have trying to work out if I am better off running one or both motors and if the props would be different in the one motor scenario over the 2 motor scenario.

I am pretty certain the props on the boat are the same as if I only had one motor and I am wondering if that is sensible.

(a 30 foot sail, about 6Te)

 

[KevinV]

My understanding is that electric motors don't like working at full bore - that they're more efficient running slower. Whether this is offset by losses by the props I don't know - I'm sure you could measure the power usage quite easily to verify.

 

[Alex_Blackwood]

My understanding is that electric motors don't like working at full bore - that they're more efficient running slower. Whether this is offset by losses by the props I don't know - I'm sure you could measure the power usage quite easily to verify.

Electric motors are most efficient at around 75% of full load. Efficiency dramatically reduces at 50% and below. So depending on how fast the OP wants to go will depend on whether one or two motors are best suited.
On ships with electric propulsion with more than one drive we always reduced the numbers running if operating at less than full power.

 

[KevinV]

Electric motors are most efficient at around 75% of full load. Efficiency dramatically reduces at 50% and below. So depending on how fast the OP wants to go will depend on whether one or two motors are best suited.
On ships with electric propulsion with more than one drive we always reduced the numbers running if operating at less than full power.

Interesting, thank you