I believe we are going to have lot of these in the near future since our president vision of year 2020 is to make Maldives carbon neutral.

I guess this would make good business for me, eh!

So now I am starting and I too have a vision.
To fix the Motor drivers. hehheheheh...

Below is the spec of a typical motor controller of a Battery operated two wheeler we have here.

From the label it is clear that china is already carbon neutral ..I mean they are the guys responsible for making the PWM.

My goal is to fix the driver at a cheap price. I got my hands on one of the faulty one, which by the way came to my, as usual, after the infamous wannabe's says it cannot be done.

My diagnostic relieved that the MOSFET's need to be replaced.
The drive config I believe is 3 phase induction motor control type.
Cycle uses two 12V batteries ( the info I got, as I haven;t yet seen the battery compartment of a typical cycle yet ).
According to the controller the motor is around 800W.
By looking at the wiring of the conroller leads me to believe it is a 3 phase induction type. Customized for cycles.

 

E-Bikes are fairly new in my area and are about to take off.
Sealed Lead Acid Batteries (SLAB) will last about two years, lithium about four years.
You will soon see a lot of e-bike riders pushing their bikes down the road in a few years.
And what about all the e-cars on the side of the road with dead batteries?

 

I believe these are the Motor Leads

Which leads to the type of Motor that I guessed

This controller has two blown MOSFET's.

Total 6 of 'em were there.
Data is provided for ur convenience.

these guys are at 80 Amps. 320A Pulsed. Pretty heavy duty but unreliable.
These Mosfets are blowing Prematurely I guess.

So looking at the specs and all what I have right now is the IRFZ44's that comes close to these. I do have IRFP260, too


I am going to give it a shot to see if they can can withstand the jolt.

So what do you think will hold ?

 

Interesting. A company gave me a couple of these controllers to see if I can build a tester for them. I never got around to it. I will open the cases and see what's inside.
I can't imagine what would blow the MOSFETS unless the timing of the drive signals were not correct. Bare in mind that the inductive load is enormous.

 

Neither of the MOSFETS that you are planning on trying have sufficient specifications. You will wind up with more dead MOSFETs.

 

Neither of the MOSFETS that you are planning on trying have sufficient specifications. You will wind up with more dead MOSFETs.

You said it like that I am dumb enough to try it...

And you are right, I am not dumb but I will try it.
So, Sgt...you are saying that I would blow 'em.......hmmmm..seems like fun!!.

But wait !..my purpose to ask was that could it be the fake component thing.
The controllers are dying just too fast

for arguments sake or whatever, let's say that the RJK are fakes and if I switch 'em to IRFZ44's ( genuine part ) wouldn't it work provided that the DC bus voltage is 48V ( four 12V 17A lead acids I think ).

The IRFZ44 has a VDS of 55V.

If the current holds, (I say this cause I dunno the actual spec of the motor), let's say supply is 24V, then wouldn't the IRF suffice Voltage vise?

 

The Vdss ratings are close; ~92%. The Rds(on) specs are MUCH higher.

It could be a poorly designed controller, insufficient heat sinking, failure to apply heat sink compound, abuse by the rider, too high of a temperature in the Maldives, corrosion, etc. - WAY too many variables for me to know about for those few photos you've supplied.

 

You might send some samples to the manufacturer, or simply write to them and see if there is a possibility that they are counterfeit. Take pictures of them from every angle, and give accurate dimensions of the devices.

 

Shooooot ! Why did I not see that,

RDS(ON)is indeed too high, 22mΩ Vs 7.9mΩ. power dissipation will be high.

Sgt, if the motor rating is lower than what I have said, would it work ?

 

Why don't you test some of the MOSFETs that seem to still be working, and verify if they meet the manufacturers' specifications or not?

If the original MOSFETs actually meet the manufacturers' specifications are failing, there is no hope that the others you are considering will work for anything other than a bench test. They will fail at less than half the rated power output.

 

What would I need to test a FET for it's specs.
I'll take ur advice and not blow some FET's I have Sgt.


OK..tomorrow I'll snap some pics of the Cycle in it's underwears..


Time to get down and dirty..

 

I'm really sorry, Rifaa - but I simply don't have the time.

Try googling: "MOSFET testing parameters" or "MOSFET test methods" or "MOSFET specification verification".

If you really want them tested properly, send the ones you have back to the manufacturer.

 

It's Okay Sgt, what you have advised is more than enuf.

I like to know what the label says though.
Where is happy when u need her ?

 

Data sheet ratings for mosfet packages are VERY over rated! They some times give a amperage raring of over a hundred amps on a data sheet- but don't tell you the package rating. The 'TO-220' package that most mosfets come in is only rated to handle 75amps, no mater what the data sheet says. And that is with the proper size heat sink and heat sink grease.

This is a link from IRF that tells the tale; http://irf.custhelp.com/cgi-bin/irf...?p_faqid=373&p_created=1060813068&p_topview=1

Question IRF3205 has a TO-220AB package. This device is rated at 110 amps. How is it possible that this package type will conduct 110 amps of current. It looks small to us and the 3 leads look too small to handle 110 amps.

Answer The value on page 1 of the data sheet has a "5" asterix against it. Footnote #5 says package limitation is 75A.

The 100A figure results from the industry standard way of defining silicon current limit by reference to an infinite heatsink, that is junction temperature is at 25C ambient temperature. Older generations of silicon had conduction properties that were inferior to copper, so with older type devices the silicon determined the conduction limit not the package type. The current generation of low Rds silicon is a more efficient conductor than copper. As a particular die is used in more than one package style we state the silicon limit as a common characteristic, again using the industry standard. Designers can then use the standard thermal equilibrium equation, which includes the Rds value, current through the part and the thermal resistances of the package and any heatsink, to determine the maximum junction temperature that will occur in their application. The actual current limit for a given package depends on what current density and therefore what voltage drop and heating in the leads and frame a designer is willing to accept. Any heat generated in the leadouts and the leadframe will heat the silicon die, increase its Rdson value and thus increase its conduction losses for a given constant current value.
Generally 75A is accepted as the practical limit for TO-220.

 

In the same vein of what shortbus is talking about, and directly related to this thread:
http://mcmanis.com/chuck/robotics/projects/esc2/FET-power.html

Chuck did a great job of explaining MOSFET ratings in layman terms. It's a must-read.