I have a generator with rated power 2.3/2.5V 2-poles, single phase, with max output 2.5/2.8V according to its literature. What is the maximum SAFE electric motor that I can instal on a milling machine, working for about 1 hour at a time? Thank you

 

Could you check your figures? Nothing but Mabuchi brush motors run on 2.5 - 2.8 volts.

How do you define -

maximum SAFE electric motor

- An answer isn't possible without some parameters.

 

Reply to Super Moderator:

I have checked the manual that came with the generator (no country of origin, but I believe China), and in fact my model 3500CL has a rated power output of 2.5/3.0 kVA. The shop assistant where I bought it from said that it could run a 1hp motor for the milling machine, but I am not willing to risk this. I do not have a motor for the milling equipment yet, so I have no idea how a suitable electric motor should be rated. What other details should I look for, on thee manual (which is all the above) or on the generator?

 

It looks to me like you may have mixed up voltage ratings with kVA ratings, which are a measure of power. Let's assume that is the case and you have a milling machine that is like a common Bridgeport. That is, it is designed for a 2 HP motor, but will run with larger or smaller motors.

A generator that puts out 2.5 to 3 kVA (about 3.4 to 4 HP)continuously is plenty. You need to consider the starting current on single phase and physical size of the motor for the mill.

1) If you are generating your own electricity, why not go three phase? It will be a cheaper motor for the mill and require less starting current.

2) As for the mill, it probably needs a C-mount motor (i.e., face mounted). The controlling element there is size. You need enough power for constant speed, and it needs to be small enough to fit on the head. I would suggest 1.5 HP as a reasonable minimum. You can go as big as you want, but something over 5 HP will give more power to the spindle than that particular mill is designed to handle. You simply shouldn't be taking such heavy cuts with a light weight shop mill.

Good luck. John

 

The one other significant issue is that of voltage output. Is it 120 VAC, 240 VAC, or some other? A KVA rating does give power, but that is a product of two things - voltage and current. Motors are particular about the voltage applied to them.

 

The rated output is 240 volts. I am currently using this generator for a smaller lathe and a drilling machine, both 240V 0.5hp, plus all the electrical fittings in the garage which is not accessible to mains electricty. Thanks all for your help, much appreciated - am a new member, joined today!!!