Someone hacks your Tesla and causes the motor to self destruct. Sounds like
something for a new James Bond film. Evil Doctor Edison causes a simultaneous
destruction of all Teslas world wide.... Bwhahahah
(BTW, saw Current Wars, good film. I actually realized something: Edison was
not full of crap when he was claiming AC was more dangerous. I always thought
of that as a BS red herring. But the film script emphasized a minor detail I
had never caught since reading my first Edison biography back in the 1960s.
The Westinghouse/Tesla AC system was ground referenced. Edison was a floating
system. Obviously it was safer. )
From: Bill Prince
Sent: Tuesday, November 12, 2019 8:41 AM
To: af@af.afmug.com
Subject: Re: [AFMUG] OT: Induction coil voltage
You know we might be in trouble if the NHTSA starts mandating shrapnel
containment in future electric cars.
bp
<part15sbs{at}gmail{dot}com>
On 11/11/2019 9:39 PM, Forrest Christian (List Account) wrote:
I go to a conference every year put on by Microchip Technologies where a lot
of us who use Microchip microcontrollers take classes put on often by the
people who are designing the actual products we're using.
Like every other conference, a big part is to meet and discuss things with
other attendees. I always love when I end up sitting at a table by people who
do high-powered motor control, typically brushless anymore. They always have
good stories to tell.
Apparently you've never experienced life until you have your code
unintentionally attempt to lock a rotor on a very very big DC motor. The
stories about having a motor self-destruct on a test rig as a result are just
scary. I think I can skip that portion of my life experience.... thank you
very much. I do enough unintentional destruction of electronics myself
without needing to add shrapnel to the mix.
On Fri, Nov 8, 2019 at 5:33 AM Mark Radabaugh <m...@amplex.net> wrote:
For our EE power class (motors, generators, etc.) they decided we should
take a lab exam. My exam time was for the second session. When the elevator
door opened on the lab floor the burnt electrical smell was pretty obvious.
Professor comes walking out of the exam with an armful of equipment heading for
the tech repair shop shaking his head and muttering something about “this was a
really bad idea”.
One would think senior level electrical engineering students would know not
to yank banana plug patch cords out of DC motors running at full speed. Or
not try to uncouple a paralleled generator by adjusting the power factor to 0
(for those of you not EE’s that leads to two generators trying to rip
themselves apart). Or measure voltage with a ammeter.
Mark
On Nov 7, 2019, at 2:27 PM, <ch...@wbmfg.com> <ch...@wbmfg.com> wrote:
In our motor lab someone asked the prof something similar like reversing
polarity to a DC motor that was fully wound up.
I don’t remember the exact question or exactly what he did but I do
remember the result.
The motor tore itself from its moorings and launched across the room..
From: Ken Hohhof
Sent: Thursday, November 7, 2019 12:15 PM
To: 'AnimalFarm Microwave Users Group'
Subject: Re: [AFMUG] OT: Induction coil voltage
I was an EE undergrad long enough ago that we had a required course
called “Electromechanical Devices”, and popularly referred to as “Motors”. It
had a lab, and none of the professors wanted to teach Motors Lab, so it usually
fell to the most junior prof, who didn’t want to be there.
We had one whose standard answer to all questions was “Let’s find out.”
Student: What happens if you open the field coil on a running DC motor?
Professor: Let’s find out.
Student: What happens if you short the output of the generator in a
motor/generator pair?
Professor: Let’s find out.
Who can guess what we found out?
Hints: a high pitched whirr, and a sudden thunk, were involved.
From: AF <af-boun...@af.afmug.com> On Behalf Of ch...@wbmfg.com
Sent: Thursday, November 7, 2019 12:53 PM
To: af@af.afmug.com
Subject: Re: [AFMUG] OT: Induction coil voltage
I used to have a flashlight that had a coil and magnet just like this.
Shake it for a while and charge a cap that is used to light the light. Can’t
remember if you could shake it and make light in real time.
But yeah, you can certainly use a rectifier and cap to make DC for a DC
motor.
From: Adam Moffett
Sent: Thursday, November 7, 2019 11:47 AM
To: af@af.afmug.com
Subject: Re: [AFMUG] OT: Induction coil voltage
A future project is going to be a primitive motor powered by a
battery....I wonder if I can shake this bugger to make the motor spin.
On 11/7/2019 1:41 PM, ch...@wbmfg.com wrote:
Yes, it is one cycle of AC.
From: Adam Moffett
Sent: Thursday, November 7, 2019 11:26 AM
To: af@af.afmug.com
Subject: Re: [AFMUG] OT: Induction coil voltage
So by the way, this activity works with a 4oz (800+ feet) roll of 30AWG
wrapped around the paper towel tube.
My next point of confusion is this:
An LED obviously has a polarity. If I connect one LED to the coil and
drop the magnet through, the LED lights for a moment. I expected that if I
drop the magnet N first and S first that it would light up one way and not the
other. Instead the LED blinks whichever way I drop the magnet. So does that
mean I am getting A/C power with this? Do I get current in one direction with
the leading edge of the magnetic field passing through the coil and then
current the other direction as the trailing edge of the field passes?
I ran out of time last night before I got to the point of hooking up
both LED's. So if this is A/C then the difference would be which color blinks
first I suppose.
The point of this was to teach the kids something about electricity,
but it's turning out that my knowledge on these fundamentals is pretty
superficial.
-Adam
On 11/3/2019 12:19 PM, Adam Moffett wrote:
I wanted to do this science experiment with the kids. My problem is
my LED's don't light up. It's from a discontinued textbook. Apparently they
sold a kit with the materials for all the projects, but that's no longer
available so I'm scrounging in the garage.
I put a volt meter on the rig and I was only getting 6mV when I
dropped the magnet. I doubled the number of coils on the tube and then doubled
the number of neodymium magnets and I'm getting closer to 30mV now, but I need
closer to 2V to light up an LED, so I'm wondering what would increase the
voltage by two orders of magnitude. Is it based on the number of turns in the
coil?
<image001.png>
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