I have an old 230v 1/3 hp motor. If i spin this motor in reverse using another motor, will it generate elec?

Question

will the first motor work like a generator if spun backwards--if so, how much power would it generate?

Answer 1

I very much doubt it.
In order to create power you must turn a magnetic field or have a wire loop cut the magnetic field.
If your motor is a typical small single phase induction motor it will not generate unless there is residual magnetism in the rotor ( unlikely to be significant )
You need a different design
some thing that either has a permanent magnet rotor or has power injected into the rotor to create a magnetic field that you would then spin. Power injected in to the rotor is a Synchronous Motor/Generator the same as what the utilities use.
Another option would be a DC system but that's another story.

Answer 2

I think you've got a misconception here.

You don't need to reverse the direction of rotation - and, most likely, doing so will cause more damage to the electric machine.

The reason for this is that a lot of these machines are designed for single rotation - this means their internal methods of cooling are based on the rotating portion moving in only one direction. To determine if this is indeed the case for your machine, check the nameplate. There should be something on it (or another small plate with an arrow) indicating preferred rotation.

All rotating equipment (whether electric or otherwise) is either a "user" of power, or a "generator" of power. To keep things simple, folks called the "user" group MOTOR and the "generator" group GENERATOR.

If you drive the rotor (the spinning part) of the machine from an outside source - like a small gas engine, or even turn it by hand - then the magnetic field will induce a current in the stationary winding. When this happens, you see voltage at the leads ... i.e. you have created "power". If, on the other hand, you apply power to the leads, you induce motion in the rotor via the forces of magnetism, and you can now achieve work by harnessing the torque produced at the machine shaft.

The amount of output power you can achieve will be determined by the amount of input power (and the speed at which rotation occurs).

Thermally, you could produce (0.746 * 0.333 hp) = 0.248 kW at 230 volts.

With all the built-in losses to the drive train (windage, friction, gearing, etc) and the probable efficiency of your driver (say a gas engine at 35%), this means you'd need to use about 0.75 kW worth of energy as a system input.

Answer 3

less than the energy you are using to turn it with

if not then we all would have a series of motors hooked up to the power lines to carry energy away from our houses

Answer 4

an electric motor is in itself a generater the voltage will be dicktated by the winding around the stator