Electric Compressor on boat, changing Single Phase to 3 Phase

[Angelo Farina]

No possibility that you can run off batteries. Change to petrol motor and all okay. Simple, cheap.

Battery-operated vehicles are the future, not the present yet.
I can foresee that in 20 years most boats will employ electric engines (either outboard or inboard), and all cars and most house systems will also be battery-powered.
Currently batteries are yet too much expensive.
At my home I have a 10 kWh battery, powered by the solar photovoltaic panels, just because the whole system was subsidised at 100% by the Italian government (the so-called "superbonus 110%").
But a 10 kWh battery is too small, I run out of juice typically at 03-04 in the morning, and I need to get power from the grid for at least 4-5h each day. I should increase it to 20 kWh (and of course expand the solar panels to a total max power of 10 kW, now it is just 6 kW).
Such a system can cost around 30000 eur. Only with 100% government subside one can afford such an expense.
The same for cars. I recently purchased a car, and having a budget of less than 20000 eur I have got a used diesel-powered Jeep Cherokee. Purchasing a full-electric SUV had costed three times more, and for this the government is providing a very small subside, so it was entirely out of my budget.
A fully-electric boat could have even larger extra costs compared to a diesel engine, around 50000 eur. For now, fully-electric vehicles are a luxury for very rich people...
I really hope that the prices will fall in the next 10 years, making fully-electric houses, cars and boats the standard for everyone.

 

[CraigAClark]

What size generator do you have, if any?

 

[2ge]

no generator for now, thinking to put 2-3kw generator for backup. I am in process to install 2x3kw inverters, so there will be 6kw power, and also adding more batteries, totally 6.6kw in batteries, adding also more solar panels + there is hydrogenerator. I will go via route 3phase engine on compressor and VFD.

 

[Gone for diving]

there is hydrogenerator

What do you mean by this?

Also one thing I have done in my work trailer for my shop compressor. Is use a 90v DC motor, with a bridge rectifier power it with 120v AC runs off my 2500watt inverter or generator, one nice thing is that, there is not surge like a AC motor.
And even when I plug in at a customers that does not have great wiring it will startup, and run slower because of line loss, but still works,
Great startup torque as well.

 

[2ge]

Hydrogenerators are something what you put in water while you are sailing, propeller is turning and it creates energy. Check out here for example Hydrogenerators - Watt and Sea

Lets see how my setup will work, but I not see any flaw for now.

 

[CraigAClark]

Straight up, minimum size genset to start a 2 hp single phase electric motor is 6KW and 3hp is 8KW. I'm pretty sure you would need the same with a frequency (inverter) drive even going with a 3 phase motor in place of the single phase motor. You will be running off of single phase supply through the drive. It shouldn't matter if the supply is 50 or 60 hertz. You should really consult a marine electrician when sizing the drive. You probably won't be saving any power because the drive and motor usage will be the same as a straight up single phase motor. The beauty is the drive will allow the motor speed to be ramped up to full speed over time. You won't get the 5 to 7 times the "inrush" power required to start a single phase motor straight up.

 

[Gone for diving]

Straight up, minimum size genset to start a 2 hp single phase electric motor is 6KW and 3hp is 8KW. I'm pretty sure you would need the same with a frequency (inverter) drive even going with a 3 phase motor in place of the single phase motor. You will be running off of single phase supply through the drive. It shouldn't matter if the supply is 50 or 60 hertz. You should really consult a marine electrician when sizing the drive. You probably won't be saving any power because the drive and motor usage will be the same as a straight up single phase motor. The beauty is the drive will allow the motor speed to be ramped up to full speed over time. You won't get the 5 to 7 times the "inrush" power required to start a single phase motor straight up.

I am no expert but I do have practical experience with my own stuff, that I build.
2 hp is 1,492watt theoretical, so for losses say 2000 watts,

If you use a vdf, the genset minimum, doesn't apply,

As I stated above.
My DC 90v PM motor draws 15 amps 1800 watts drives a 4 cfm 150 psi shop air compressor,
I can run it on 2500 watt HF inverter or my 2500 watt inverter generator no problem.
Has super start up torque, Will startup with 120 psi with no unloader.
I don't know why DC motor are not more popular, (sure the brushes can wear out)
But the advantages out weigh the cons for alot of stuff.

oh did I mention I have converted my drill press to go slower and use a DC treadmill motor with variable speed...
Treadmill motors are great 90v DC motors only problem is max rpm and hp rating is about 5000 rpms.

 

[BRT]

Straight up, minimum size genset to start a 2 hp single phase electric motor is 6KW and 3hp is 8KW. I'm pretty sure you would need the same with a frequency (inverter) drive even going with a 3 phase motor in place of the single phase motor. You will be running off of single phase supply through the drive. It shouldn't matter if the supply is 50 or 60 hertz. You should really consult a marine electrician when sizing the drive. You probably won't be saving any power because the drive and motor usage will be the same as a straight up single phase motor. The beauty is the drive will allow the motor speed to be ramped up to full speed over time. You won't get the 5 to 7 times the "inrush" power required to start a single phase motor straight up.

No, not with a VSD or a soft start.

 

[CraigAClark]

No, not with a VSD or a soft start.

I did say "straight up"

 

[BRT]

I did say "straight up"

What you said was" I'm pretty sure you would need the same with a frequency (inverter) drive even going with a 3 phase motor in place of the single phase motor.