IRFP-450 Mos Fet Harris

[polar bear6]

i came across a guy thats selling 300 mosfets, and i wondered if they are suitable for making H bridges or other cool robotic stuff.
heres a data sheet.
http://pdf1.alldatasheet.com/datasheet-pdf/view/22408/STMICROELECTRONICS/IRFP450.html
I'm really not very good at reading datasheets since i don't know what the things are called and how much current or voltage it needs and stuff, so if anyone could help me it would be really great 

[Admin]

how much? digikey is selling them for $3 each (at the moment out of stock, and 8 years old technology). 300 is a bit much, as ive only used about 20 mosfets in the last 4 years.

skimming through the datasheet, it looks like a useful power mosfet. i recommend buying maybe 5 or 10 of them (if you can get them under $2 each) - as you get better in robotics you will find them useful to keep around.

if you have specific questions on reading datasheets, i encourage you to ask. its an important skill to have for robot building 

[polar bear6]

he is selling 300 for about 32$.
thats without the shipping, the whole schazam weights 2,2 kilos  so the shipping will cost some money too, but i am going to buy some others stuff from him too. i think he had an electronic shop and it didnt work out as well as he thought and now hes just selling it all.
hes selling these big packages that costs 500-1000$ new for just 70-150$.
i have bought from him before so i know he delivers what he say he sells...

[Militoy]

I'm using Harris IRFP150s and 250s, which are in the same family; as well as IRFP340s, 352s and 264s in half and full bridges in military power supplies. They're excellent parts for bridges - in certain applications. Even though their Rds(on) rating of .33 ohms isn't near as low as the newer generation of FETs, it's still respectably low for a 500 Volt transistor. At any current over about 2 Amps, it's going to have a higher forward voltage drop than a silicon transistor - but it should be easier to drive on into saturation. If you're planning to switch low voltage at high currents, you would need to use more than one in parallel, in order to lower your forward voltage drop. For higher voltages at lower current - they are pretty good. At $0.11 each - you really can't lose.

[polar bear6]

okey thanks for the reply, but i wonderd since its a 500 volts transistor, will it be usable for driving 6-24v motors?
i really dont have any plans making robots that use 500v...

[Militoy]

The higher voltage parts will work OK. You will just (generally) get lower forward voltage drop from a lower voltage transistor. You wouldn't want to use a 500V FET at 500 Volts, anyway. You need to leave a little headroom as a safety factor from switching voltage spikes, input voltage variation, etc. I usually try to select a transistor rated for around twice the voltage I will be using it at (same goes for caps).

[Admin]

I usually try to select a transistor rated for around twice the voltage I will be using it at (same goes for caps).

I completely agree. Ive seen too many caps explode from people who forget this . . . reversing a motor already at full forward speed would cause the spike . . .

You might also want to consider using a mosfet driver to boost efficiency. The one I use is IXDD404PI made by IXYS. Its listed as '4 Amp Dual Low-Side Ultrafast MOSFET Driver.'

The higher the mosfet gate voltage, the higher the efficiency (reduced heat output, too). This is the advantage of using the driver.

ps -
Not sure how reliable this chip is (or if I just didnt account for something in my circuit) . . . I used it for like 4 months with no problem . . . then the day a representive from ONR came by to see my prototype it went up in smoke for no reason . . . blast you, murphy and your law!

[Cognaut]

It sounds like another case of "tin whiskers."    

[Admin]

interesting . . . never heard of it before . . .
http://en.wikipedia.org/wiki/Whisker_(metallurgy)

im sure the fact that my circuit board was never more than 2 feet away from a large fish tank for all those months had something to do with it . . . 
(the curse of aquatic robotics)

[Militoy]

ICs and hybrid modules have become more and more reliable in recent years – and a catastrophic failure is now usually the result of the designer or user exceeding some Absolute Maximum Rating parameter of the part that failed – as opposed to “Infant Mortality”. ESD over-voltage damage from improper handling is a common culprit, as are un-planned-for voltage transients, over-temperature, or just plain making mistakes in the design application. There are no mysteries in electronics design – sometimes though, you just haven’t gathered enough data to understand a situation.

Re: tin Whiskering – The growth of tin sulfide whiskers on tinned component leads, and their effect on the solderability of the affected parts has been a major problem in military electronics for years. The problem results from the use of pure tin to plate solderable leads. When placed in proximity with a cardboard box or paper which is processed with acid, the outgassing of sulfur dioxide from the paper causes the growth of tin sulfide crystals, or “whiskers” on the plated surfaces. Soldering of the leads is then difficult or impossible, and failure of the soldered joint is not unusual. Most defense contractors have requirements in their specifications that the tin plating on component leads contain at least 3% lead in the alloy, in order to prevent whiskering. The problem becomes very tricky, as European ROHS standards prohibit the use of lead on component leads – so all the parts manufacturers are omitting lead from their plating process.