alternator question

[Garth]

im sure those who are electricaly minded would now it takes a fair bit of energy to make electricity.

im chasing some info.
how much force is required to be exerted on a alternator in a car to alow the generation of electricity.

and there is a term that is comming to mind, im thinking saturation, nto sure if it's the right term, but where the alternator is at it's peak, and it simply stops working. is that the term, saturation?

[Anonymous]

Originally Posted by Garth

how much force is required to be exerted on a alternator in a car to alow the generation of electricity.

I changed the acc belt over last week and gave all the pulleys a turn to see what condition they were in. The alternator pulley felt like there was nothing behind it! Could spin it freely.

I always thought it would be hard to turn. Learn something new every day.

[kopper69]

Originally Posted by Anonymous

I changed the acc belt over last week and gave all the pulleys a turn to see what condition they were in. The alternator pulley felt like there was nothing behind it! Could spin it freely.

I always thought it would be hard to turn. Learn something new every day.

When the alternator is working, as in there is a load connected, it would be impossible to spin by hand.

Garth, I may not have followed your question totally, so if I dont answer it correctly can you explain a little further.

In your car you have an alternator. The alternator may be rated at 65A. This means that the maximum current that the alternator can put out is 65A. This is only when the car needs it though. When the battery needs charging and you are running lights and electrical accessories, the alternator may be providing a full 65A. If the battery is charged and lights are on, the alternator needs to provide power for the lights, but not charge the battery, so may only be providing 30A. When the lights are off and battery is charged there is little current required by the system and the alternator may only be putting out 10A.

The more current required, the harder the engine has to work to turn the alternator. If you feel like a bit of an experiment get yourself a little electric motor, dick smith whatever. When you turn the motor you produce power. If you put a load on the motor while you turn it, you will find the motor is much harder to turn. You will also find out that as you turn the motor faster you will produce more power to a point. At some stage, the motors rated speed, you can turn faster and faster and the motor wont provide any more power.

[commsirac]

Garth, you are asking how much force? to turn the alternator? it depends on the size of the pulley and what rpm its spinning at, probably best to talk in power terms
Typically alternators are only 60-70% efficient, so for a alternator putting out 60A at 14V, its going to take ~1.3kW of the motor.

[Anonymous]

Originally Posted by kopper69

When the alternator is working, as in there is a load connected, it would be impossible to spin by hand.

Ah cheers. Was thinking something along those lines.

[baracuda]

yehh thats right. the bearings front and back in the alternator makes it spin freely and can be spun around with hand. if it makes a noise or a dry grinding sound you know the bearings on way out. you require over 300rpm to get the wiring etc in the alternator exited to generate electricity.

Originally Posted by Anonymous

I changed the acc belt over last week and gave all the pulleys a turn to see what condition they were in. The alternator pulley felt like there was nothing behind it! Could spin it freely.

I always thought it would be hard to turn. Learn something new every day.