[brian_]

The current fuel engine is 14hp. What would be a correct size for electric motor (kW)? Would 5kW be enough? I’ve understood the effiency is a lot better with these. But unfortunately I don’t have specs of the hydraulic pump with me here.

Efficiency has nothing to do with motor or engine sizing, since they are rated by their output (efficiency is the ratio of output power to input power).

For the same performance, you need to match the maximum output of the electric motor to the maximum output of the original engine, and match the continuous output of the electric motor to the continuous output of the original engine. It's unlikely that the original engine was used at 14 horsepower continuously, and it's likely that an electric motor advertised as "5 kW" can actually produce 5 kW continuously for any useful period of time.

Assuming that everything in the machine is driven through the hydraulic system, it would be very helpful to have the hydraulic pump specs. You would certainly have enough motor if you chose one which can run at 10 kW (about 14 hp) continuously, and provided a drive (gear, belt, or chain) as necessary so the motor can run at the speed it needs to produce that power; you can probably get away with one that can intermittently run at 10 kW and continuously run a lower power... 5 kW may be reasonable.

 

[vmaijala]

Thanks Brian.

Yes, I forgot to mention that everything is driven through the hydraulic system, as you assumed. Both front wheels have hydraulic motors and there are chains from front to rear wheels.

And you are right, it would be better to know the specs off the hydraulic pump. As it is currently located 160km away I need to wait with the motor decision until I get to it. I assume max rpm and torque are something to consider there? One option I have is 11kW motor from electric forklift. If it only fits physically there would be some spare power I assume.

What should be taken into account while selecting (speed) controller for the motor? And is there some brands recommended?

 

[brian_]

And you are right, it would be better to know the specs off the hydraulic pump. As it is currently located 160km away I need to wait with the motor decision until I get to it. I assume max rpm and torque are something to consider there?

To determine how much power the pump could need, the hydraulic pressure and flow rate would be needed. To determine any mechanical drive system needed, the speed of the pump at maximum flow would be compared to the electric motor speed for maximum power. Although the combination of power and speed determine the torque, you don't need to know the torque specifically, and I expect that a pump's specifications typically won't include a required drive torque.

One option I have is 11kW motor from electric forklift. If it only fits physically there would be some spare power I assume.

That sounds promising. A moderately more powerful motor than required is harmless, other than the increased weight and cost.