What is a freewheel diode ?

What does it mean by "freewheel diode"?

Re: freewheel diode

It is an expression used to refer a diode that holds(or assume) an inductor current.

For example, you can imagine an inductor with a diode in parallel. Now connect a voltage source in this circuit (also in parallel) in such way that the diode stay reversely biased. Your inductor will charge.. right? Now simply disconnect the the voltage source.... So, what will happen?
You can note that the current was flowing on the inductor in a direction that will direct polarize the diode, so the diode will conduct. As the voltage drop in the diode is almost zero (depends of the case) the current that was charged in the inductor will be keeped flowing through the diode.
Then, such diode is called "freewhell diode".

This situation occurs in many cases, but in most of them there are yet a voltage source between the diode and the inductor, what is necessary to discharge the inductor. It is what happen in all DC-DC converter (switched mode power supply), for example, the buck and boost converters.

I hope it will be helpfull... any doubt, simply ask.

Re: freewheel diode

I agree also a freewheel diode is placed across the motor in a H-Bridge configuration. This is reguired as the motor acts as a generator during freewheel, and generated current that needs to be dumped

cheers
slayerza

Re: freewheel diode

a freewheeling diode basically means it is used to freewheel the current

in many power elns circuits when there is a current in the load but suddenly sitches/thyristors turn off...the current/energy has nowhere to go...to ensure continuity of current in the load a diode (forward biased/allowing this current) is connected in parallel to the load of the circuit.

hope it helps u....rashid(power elns) is quite gud...
cheers..........