MOV curve...

[John Larkin]

I always thought MOVs were sloppy, but they are actually pretty cool.

https://www.dropbox.com/s/9axwbhmmnd460n5/Littlefuse_V25S150P_EI.jpg?raw=1

We blew up a channel in our alternator simulator, probably some crazy
flyback voltage from the simulated load, so I\'m going to add an MOV
across each of the output phases. This one can absorb 22,000 amps and
300 joules.

390 volts max at 100 amps.

The low part of the curve looks very exponential. Someone once sold a
MOV type part as an analog computing element.

 

[Joerg]

On 2020-07-31 12:13, John Larkin wrote:

I always thought MOVs were sloppy, but they are actually pretty cool.

https://www.dropbox.com/s/9axwbhmmnd460n5/Littlefuse_V25S150P_EI.jpg?raw=1

We blew up a channel in our alternator simulator, probably some crazy
flyback voltage from the simulated load, so I\'m going to add an MOV
across each of the output phases. This one can absorb 22,000 amps and
300 joules.

390 volts max at 100 amps.

The low part of the curve looks very exponential. Someone once sold a
MOV type part as an analog computing element.

Just keep in mind that MOVs are \"consumables\". They get eaten up a
little bit with every jolt until one fine day ... KABLOUIE.

--
Regards, Joerg

http://www.analogconsultants.com/

 

[Phil Hobbs]

On 2020-07-31 15:52, Joerg wrote:

On 2020-07-31 12:13, John Larkin wrote:
I always thought MOVs were sloppy, but they are actually pretty cool.

https://www.dropbox.com/s/9axwbhmmnd460n5/Littlefuse_V25S150P_EI.jpg?raw=1


We blew up a channel in our alternator simulator, probably some crazy
flyback voltage from the simulated load, so I\'m going to add an MOV
across each of the output phases. This one can absorb 22,000 amps and
300 joules.

390 volts max at 100 amps.

The low part of the curve looks very exponential. Someone once sold a
MOV type part as an analog computing element.



Just keep in mind that MOVs are \"consumables\". They get eaten up a
little bit with every jolt until one fine day ... KABLOUIE.

Also the leakage at the low-voltage end probably deteriorates quite a
bit after some punishment.

Cheers

Phil Hobbs


--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC / Hobbs ElectroOptics
Optics, Electro-optics, Photonics, Analog Electronics
Briarcliff Manor NY 10510

http://electrooptical.net
http://hobbs-eo.com

 

[John Larkin]

On Fri, 31 Jul 2020 12:52:54 -0700, Joerg <news@analogconsultants.com>
wrote:

On 2020-07-31 12:13, John Larkin wrote:
I always thought MOVs were sloppy, but they are actually pretty cool.

https://www.dropbox.com/s/9axwbhmmnd460n5/Littlefuse_V25S150P_EI.jpg?raw=1

We blew up a channel in our alternator simulator, probably some crazy
flyback voltage from the simulated load, so I\'m going to add an MOV
across each of the output phases. This one can absorb 22,000 amps and
300 joules.

390 volts max at 100 amps.

The low part of the curve looks very exponential. Someone once sold a
MOV type part as an analog computing element.



Just keep in mind that MOVs are \"consumables\". They get eaten up a
little bit with every jolt until one fine day ... KABLOUIE.

Better a later kablouie than a sooner one.

I don\'t expect much integrated clamping energy over time.

Here\'s my ECO:

https://www.dropbox.com/s/q2hh42595usk770/P903_E2.jpg?raw=1

Each phase of my sinewave generator is transformer isolated, and
during a test we blew up some 1206 divider resistors, a big RC
snubber, and cracked an ADUM7703 isolator chip rated for 5700 VRMS.
All that was clearly impossible and can\'t be reproduced. There was way
too much energy for it to be ESD. So the MOVs and caps might help.

So each phase now has an MOV hi-lo and another lo-gnd. The caps across
the transformer secondaries may help too, and also reduce feedthru
fuzz from the big class-D amps.

 

[Joerg]

On 2020-07-31 14:08, John Larkin wrote:

On Fri, 31 Jul 2020 12:52:54 -0700, Joerg <news@analogconsultants.com
wrote:

On 2020-07-31 12:13, John Larkin wrote:
I always thought MOVs were sloppy, but they are actually pretty cool.

https://www.dropbox.com/s/9axwbhmmnd460n5/Littlefuse_V25S150P_EI.jpg?raw=1

We blew up a channel in our alternator simulator, probably some crazy
flyback voltage from the simulated load, so I\'m going to add an MOV
across each of the output phases. This one can absorb 22,000 amps and
300 joules.

390 volts max at 100 amps.

The low part of the curve looks very exponential. Someone once sold a
MOV type part as an analog computing element.



Just keep in mind that MOVs are \"consumables\". They get eaten up a
little bit with every jolt until one fine day ... KABLOUIE.

Better a later kablouie than a sooner one.

I don\'t expect much integrated clamping energy over time.

Here\'s my ECO:

https://www.dropbox.com/s/q2hh42595usk770/P903_E2.jpg?raw=1

Very nice rework, almost looks like it was always planned that way.

Each phase of my sinewave generator is transformer isolated, and
during a test we blew up some 1206 divider resistors, a big RC
snubber, and cracked an ADUM7703 isolator chip rated for 5700 VRMS.
All that was clearly impossible and can\'t be reproduced. There was way
too much energy for it to be ESD. So the MOVs and caps might help.

So each phase now has an MOV hi-lo and another lo-gnd. The caps across
the transformer secondaries may help too, and also reduce feedthru
fuzz from the big class-D amps.

It can be ok as long as this transient load isn\'t repetitive. Otherwise
I\'d rather use TVS.

--
Regards, Joerg

http://www.analogconsultants.com/

 

[John Larkin]

On Fri, 31 Jul 2020 14:56:54 -0700, Joerg <news@analogconsultants.com>
wrote:

On 2020-07-31 14:08, John Larkin wrote:
On Fri, 31 Jul 2020 12:52:54 -0700, Joerg <news@analogconsultants.com
wrote:

On 2020-07-31 12:13, John Larkin wrote:
I always thought MOVs were sloppy, but they are actually pretty cool.

https://www.dropbox.com/s/9axwbhmmnd460n5/Littlefuse_V25S150P_EI.jpg?raw=1

We blew up a channel in our alternator simulator, probably some crazy
flyback voltage from the simulated load, so I\'m going to add an MOV
across each of the output phases. This one can absorb 22,000 amps and
300 joules.

390 volts max at 100 amps.

The low part of the curve looks very exponential. Someone once sold a
MOV type part as an analog computing element.



Just keep in mind that MOVs are \"consumables\". They get eaten up a
little bit with every jolt until one fine day ... KABLOUIE.

Better a later kablouie than a sooner one.

I don\'t expect much integrated clamping energy over time.

Here\'s my ECO:

https://www.dropbox.com/s/q2hh42595usk770/P903_E2.jpg?raw=1


Very nice rework, almost looks like it was always planned that way.


Each phase of my sinewave generator is transformer isolated, and
during a test we blew up some 1206 divider resistors, a big RC
snubber, and cracked an ADUM7703 isolator chip rated for 5700 VRMS.
All that was clearly impossible and can\'t be reproduced. There was way
too much energy for it to be ESD. So the MOVs and caps might help.

So each phase now has an MOV hi-lo and another lo-gnd. The caps across
the transformer secondaries may help too, and also reduce feedthru
fuzz from the big class-D amps.


It can be ok as long as this transient load isn\'t repetitive. Otherwise
I\'d rather use TVS.

This MOV can gobble 300 joules and 20K amps!

PM alternators are inductive AC voltage sources. As speed goes up,
open-circuit voltage and frequency both go up linearly, so they
approach constant-current sources. They are typically regulated by
shorting a 3-phase full-wave bridge (3 diodes, 3 mosfets). Un-shorting
had better be done carefully or you might see a lot of volts.

 

[Piotr Wyderski]

Joerg wrote:

Just keep in mind that MOVs are \"consumables\". They get eaten up a
little bit with every jolt until one fine day ... KABLOUIE.

Buy a 3-terminal MOV with built-in overheating protection.
That way you will be able to issue a warning that the MOV is dead and
the channel is no longer protected.

Best regards, Piotr

 

[Piotr Wyderski]

John Larkin wrote:

> This MOV can gobble 300 joules and 20K amps!

It can, but this energy fuses more and more oxide grains and the current
goes up. This heating will cause a regular MOV to explode eventually or
disconnect a thermally protected one from the circuit.

PM alternators are inductive AC voltage sources. As speed goes up,
open-circuit voltage and frequency both go up linearly, so they
approach constant-current sources. They are typically regulated by
shorting a 3-phase full-wave bridge (3 diodes, 3 mosfets). Un-shorting
had better be done carefully or you might see a lot of volts.

You are wearing out your MOVs that way.

Best regards, Piotr

 

[John Larkin]

On Sat, 1 Aug 2020 01:02:48 +0200, Piotr Wyderski
<peter.pan@neverland.mil> wrote:

John Larkin wrote:

This MOV can gobble 300 joules and 20K amps!

It can, but this energy fuses more and more oxide grains and the current
goes up. This heating will cause a regular MOV to explode eventually or
disconnect a thermally protected one from the circuit.

PM alternators are inductive AC voltage sources. As speed goes up,
open-circuit voltage and frequency both go up linearly, so they
approach constant-current sources. They are typically regulated by
shorting a 3-phase full-wave bridge (3 diodes, 3 mosfets). Un-shorting
had better be done carefully or you might see a lot of volts.

You are wearing out your MOVs that way.

Best regards, Piotr

The MOVs are not expected to conduct in normal operation. If they do,
they save a lot of expensive parts. If they eventually short, it\'s a
lot easier to fix than the other things that would have exploded.

We were simulating a FADEC voltage regulator and can\'t imagine what
went wrong. And we hope that MOVs will keep it from happening again.

We have software snooping our output current, and it\'s supposed to
shut down our amps if we see too much current... before transformers
or MOVs melt down.

Power electronics can be fun, until it blows up. That tends to wreck a
*lot* of stuff that\'s hard to find and fix. Luckily, this event only
blew up a few parts, and they were obvious.

 

[Tony Stewart]

On Fri. 31 Jul.-20 7:32 p.m., John Larkin wrote:

On Sat, 1 Aug 2020 01:02:48 +0200, Piotr Wyderski
peter.pan@neverland.mil> wrote:

John Larkin wrote:

This MOV can gobble 300 joules and 20K amps!

It can, but this energy fuses more and more oxide grains and the current
goes up. This heating will cause a regular MOV to explode eventually or
disconnect a thermally protected one from the circuit.

PM alternators are inductive AC voltage sources. As speed goes up,
open-circuit voltage and frequency both go up linearly, so they
approach constant-current sources. They are typically regulated by
shorting a 3-phase full-wave bridge (3 diodes, 3 mosfets). Un-shorting
had better be done carefully or you might see a lot of volts.

You are wearing out your MOVs that way.

Best regards, Piotr

The MOVs are not expected to conduct in normal operation. If they do,
they save a lot of expensive parts. If they eventually short, it\'s a
lot easier to fix than the other things that would have exploded.

We were simulating a FADEC voltage regulator and can\'t imagine what
went wrong. And we hope that MOVs will keep it from happening again.

We have software snooping our output current, and it\'s supposed to
shut down our amps if we see too much current... before transformers
or MOVs melt down.

Power electronics can be fun, until it blows up. That tends to wreck a
*lot* of stuff that\'s hard to find and fix. Luckily, this event only
blew up a few parts, and they were obvious.

The 3phase diode bridges in automotive Alternators must handle the load
dump from the Joules in e-clutches, ACU\'s and starters. Yet the diodes
are most often the 1st parts to fail in an alternator. Is it possible
to choose MOSFETs gated by overvoltage to shunt the BEMF?

 

[boB]

On Fri, 31 Jul 2020 16:32:11 -0700, John Larkin
<jlarkin@highland_atwork_technology.com> wrote:

On Sat, 1 Aug 2020 01:02:48 +0200, Piotr Wyderski
peter.pan@neverland.mil> wrote:

John Larkin wrote:

This MOV can gobble 300 joules and 20K amps!

It can, but this energy fuses more and more oxide grains and the current
goes up. This heating will cause a regular MOV to explode eventually or
disconnect a thermally protected one from the circuit.

PM alternators are inductive AC voltage sources. As speed goes up,
open-circuit voltage and frequency both go up linearly, so they
approach constant-current sources. They are typically regulated by
shorting a 3-phase full-wave bridge (3 diodes, 3 mosfets). Un-shorting
had better be done carefully or you might see a lot of volts.

You are wearing out your MOVs that way.

Best regards, Piotr

The MOVs are not expected to conduct in normal operation. If they do,
they save a lot of expensive parts. If they eventually short, it\'s a
lot easier to fix than the other things that would have exploded.

We were simulating a FADEC voltage regulator and can\'t imagine what
went wrong. And we hope that MOVs will keep it from happening again.

We have software snooping our output current, and it\'s supposed to
shut down our amps if we see too much current... before transformers
or MOVs melt down.

Power electronics can be fun, until it blows up. That tends to wreck a
*lot* of stuff that\'s hard to find and fix. Luckily, this event only
blew up a few parts, and they were obvious.

When it blows up, if you\'re lucky, you get the technician to fix it.

Better yet, get the tech to do the test. We call them expendable
technicians.


We use a LOT of MOVs. 35mm ones for lightning protection (SPDs)

Here is what happens, during a UL test, when they are tested for
overload before the correct MOV fuse is designed in with about 500V
DC and a current limit of 10,000 amps....

https://www.eskimo.com/~bgudgel/Bang-Pop.mp4


This is not what happens during a typical lightning strike, assuming
it isn\'t a direct strike to the system grid wires or PV array, etc.

30,000 amps no problem for a typical short-ish strike.

 

[boB]

On Sat, 1 Aug 2020 00:57:12 +0200, Piotr Wyderski
<peter.pan@neverland.mil> wrote:

Joerg wrote:

Just keep in mind that MOVs are \"consumables\". They get eaten up a
little bit with every jolt until one fine day ... KABLOUIE.

Buy a 3-terminal MOV with built-in overheating protection.
That way you will be able to issue a warning that the MOV is dead and
the channel is no longer protected.

Best regards, Piotr

Tee-MOVs. That\'s what we use in our SPDs and also LEDs to indicate.
If the LED turns OFF, then there is now power or the fuse is open.

Unfortunately, for the UL 1449 certs, that internal melting solder
protection didn\'t work for these some times asinine requirements so
we had to make our own low temperature solder fuse that would open
under the specified conditions for the test.


https://www.solar-electric.com/midnite-solar-mnspd-300-ac-surge-protector.html?gclid=Cj0KCQjwgo_5BRDuARIsADDEntTKw-bpIO9MurNsjpEHRdJ0lKugIEaIAZWpu7Cr-isuTRrvm2asSE8aAtO6EALw_wcB

 

[server]

On Fri, 31 Jul 2020 19:09:46 -0700, boB <boB@K7IQ.com> wrote:

On Fri, 31 Jul 2020 16:32:11 -0700, John Larkin
jlarkin@highland_atwork_technology.com> wrote:

On Sat, 1 Aug 2020 01:02:48 +0200, Piotr Wyderski
peter.pan@neverland.mil> wrote:

John Larkin wrote:

This MOV can gobble 300 joules and 20K amps!

It can, but this energy fuses more and more oxide grains and the current
goes up. This heating will cause a regular MOV to explode eventually or
disconnect a thermally protected one from the circuit.

PM alternators are inductive AC voltage sources. As speed goes up,
open-circuit voltage and frequency both go up linearly, so they
approach constant-current sources. They are typically regulated by
shorting a 3-phase full-wave bridge (3 diodes, 3 mosfets). Un-shorting
had better be done carefully or you might see a lot of volts.

You are wearing out your MOVs that way.

Best regards, Piotr

The MOVs are not expected to conduct in normal operation. If they do,
they save a lot of expensive parts. If they eventually short, it\'s a
lot easier to fix than the other things that would have exploded.

We were simulating a FADEC voltage regulator and can\'t imagine what
went wrong. And we hope that MOVs will keep it from happening again.

We have software snooping our output current, and it\'s supposed to
shut down our amps if we see too much current... before transformers
or MOVs melt down.

Power electronics can be fun, until it blows up. That tends to wreck a
*lot* of stuff that\'s hard to find and fix. Luckily, this event only
blew up a few parts, and they were obvious.




When it blows up, if you\'re lucky, you get the technician to fix it.

When a thing blows up, it\'s my responsibility to find out why, and see
if a design mistake caused the failure. I can\'t delgate that, although
I can often get help running experiments.

We don\'t have engineering technicians.

Better yet, get the tech to do the test. We call them expendable
technicians.


We use a LOT of MOVs. 35mm ones for lightning protection (SPDs)

Here is what happens, during a UL test, when they are tested for
overload before the correct MOV fuse is designed in with about 500V
DC and a current limit of 10,000 amps....

https://www.eskimo.com/~bgudgel/Bang-Pop.mp4


This is not what happens during a typical lightning strike, assuming
it isn\'t a direct strike to the system grid wires or PV array, etc.

30,000 amps no problem for a typical short-ish strike.

The aircraft regulators have lightning protection, even thought the
FADEC is just a couple of feet from the alternator, both inside the
engine housing.

I guess a strike can make a big ground loop.




--

John Larkin Highland Technology, Inc

Science teaches us to doubt.

Claude Bernard

 

[server]

On Fri, 31 Jul 2020 21:07:25 -0400, Tony Stewart
<tony.sunnysky@gmail.com> wrote:

On Fri. 31 Jul.-20 7:32 p.m., John Larkin wrote:
On Sat, 1 Aug 2020 01:02:48 +0200, Piotr Wyderski
peter.pan@neverland.mil> wrote:

John Larkin wrote:

This MOV can gobble 300 joules and 20K amps!

It can, but this energy fuses more and more oxide grains and the current
goes up. This heating will cause a regular MOV to explode eventually or
disconnect a thermally protected one from the circuit.

PM alternators are inductive AC voltage sources. As speed goes up,
open-circuit voltage and frequency both go up linearly, so they
approach constant-current sources. They are typically regulated by
shorting a 3-phase full-wave bridge (3 diodes, 3 mosfets). Un-shorting
had better be done carefully or you might see a lot of volts.

You are wearing out your MOVs that way.

Best regards, Piotr

The MOVs are not expected to conduct in normal operation. If they do,
they save a lot of expensive parts. If they eventually short, it\'s a
lot easier to fix than the other things that would have exploded.

We were simulating a FADEC voltage regulator and can\'t imagine what
went wrong. And we hope that MOVs will keep it from happening again.

We have software snooping our output current, and it\'s supposed to
shut down our amps if we see too much current... before transformers
or MOVs melt down.

Power electronics can be fun, until it blows up. That tends to wreck a
*lot* of stuff that\'s hard to find and fix. Luckily, this event only
blew up a few parts, and they were obvious.



The 3phase diode bridges in automotive Alternators must handle the load
dump from the Joules in e-clutches, ACU\'s and starters. Yet the diodes
are most often the 1st parts to fail in an alternator. Is it possible
to choose MOSFETs gated by overvoltage to shunt the BEMF?

Car alternators are usually controlled by adjusting the field current,
so all they need is a plain diode bridge. PM alternators have no
control, so they are regulated by PWM shorting. The usual config is an
open wye connected to a bridge made of three diodes and three mosfets.
When the fets are off, their substrate diodes complete the bridge. If
you turn all three on, it shorts the alternator and there\'s no output
from the bridge. The fet sources can be grounded, so the single gate
driver is easy. That\'s fairly clever.



--

John Larkin Highland Technology, Inc

Science teaches us to doubt.

Claude Bernard

 

[Jan Panteltje]

On a sunny day (Fri, 31 Jul 2020 12:13:37 -0700) it happened John Larkin
<jlarkin@highland_atwork_technology.com> wrote in
<8nq8if153h9ivuqtpeobrg2v3foir3ou4b@4ax.com>:

I always thought MOVs were sloppy, but they are actually pretty cool.

https://www.dropbox.com/s/9axwbhmmnd460n5/Littlefuse_V25S150P_EI.jpg?raw=1

We blew up a channel in our alternator simulator, probably some crazy
flyback voltage from the simulated load, so I\'m going to add an MOV
across each of the output phases. This one can absorb 22,000 amps and
300 joules.

390 volts max at 100 amps.

The low part of the curve looks very exponential. Someone once sold a
MOV type part as an analog computing element.

I have a little mains protector thing that has both VDRs and spark-gaps,
http://panteltje.com/pub/mains_protector_IXIMG_0501.JPG

The spark gaps are from both mains poles to mains ground,
the 3 VDRs are between the mains, neutral and ground.
The neon is just to show there is power.
Was 5 $ or so 20 years ago on the local market...
http://panteltje.com/pub/mains_protector_IXIMG_0503.JPG
Protects my PCs and some other stuff.
Thunder cloud just passed over...
Shows how to make spark-gaps!

 

[whit3rd]

On Friday, July 31, 2020 at 7:09:51 PM UTC-7, boB wrote:

We use a LOT of MOVs. 35mm ones for lightning protection (SPDs)

Here is what happens, during a UL test, when they are tested for
overload before the correct MOV fuse is designed in with about 500V
DC and a current limit of 10,000 amps....

https://www.eskimo.com/~bgudgel/Bang-Pop.mp4


This is not what happens during a typical lightning strike, assuming
it isn\'t a direct strike to the system grid wires or PV array, etc.

30,000 amps no problem for a typical short-ish strike.

Nice little spark!

The traditional lightning arrestors in open country are (1) a non-resistor spark plug
(expendable) and... (2) tie a knot in any important line cord. Every little bt of indictance helps.

 

[Jan Panteltje]

Correction, looks like 2 VDRs are in series with the spark gaps...
and the third one between neutral and ground.
http://panteltje.com/pub/mains_protector_IXIMG_0504.JPG
all VDRs are the same, marked 14D471K (230V system here).

 

[Piotr Wyderski]

boB wrote:

Tee-MOVs. That\'s what we use in our SPDs and also LEDs to indicate.
If the LED turns OFF, then there is now power or the fuse is open.

I use neon bulbs for the same purpose, but wired differently. If the
bulb lights on, you need to replace your MOV. The color is right for a
warning and there is smaller current consumption when everything is OK.

Best regards, Piotr

 

[John Larkin]

On Fri, 31 Jul 2020 19:32:24 -0700, jlarkin@highlandsniptechnology.com
wrote:

On Fri, 31 Jul 2020 21:07:25 -0400, Tony Stewart
tony.sunnysky@gmail.com> wrote:

On Fri. 31 Jul.-20 7:32 p.m., John Larkin wrote:
On Sat, 1 Aug 2020 01:02:48 +0200, Piotr Wyderski
peter.pan@neverland.mil> wrote:

John Larkin wrote:

This MOV can gobble 300 joules and 20K amps!

It can, but this energy fuses more and more oxide grains and the current
goes up. This heating will cause a regular MOV to explode eventually or
disconnect a thermally protected one from the circuit.

PM alternators are inductive AC voltage sources. As speed goes up,
open-circuit voltage and frequency both go up linearly, so they
approach constant-current sources. They are typically regulated by
shorting a 3-phase full-wave bridge (3 diodes, 3 mosfets). Un-shorting
had better be done carefully or you might see a lot of volts.

You are wearing out your MOVs that way.

Best regards, Piotr

The MOVs are not expected to conduct in normal operation. If they do,
they save a lot of expensive parts. If they eventually short, it\'s a
lot easier to fix than the other things that would have exploded.

We were simulating a FADEC voltage regulator and can\'t imagine what
went wrong. And we hope that MOVs will keep it from happening again.

We have software snooping our output current, and it\'s supposed to
shut down our amps if we see too much current... before transformers
or MOVs melt down.

Power electronics can be fun, until it blows up. That tends to wreck a
*lot* of stuff that\'s hard to find and fix. Luckily, this event only
blew up a few parts, and they were obvious.



The 3phase diode bridges in automotive Alternators must handle the load
dump from the Joules in e-clutches, ACU\'s and starters. Yet the diodes
are most often the 1st parts to fail in an alternator. Is it possible
to choose MOSFETs gated by overvoltage to shunt the BEMF?

Car alternators are usually controlled by adjusting the field current,
so all they need is a plain diode bridge. PM alternators have no
control, so they are regulated by PWM shorting. The usual config is an
open wye connected to a bridge made of three diodes and three mosfets.
When the fets are off, their substrate diodes complete the bridge. If
you turn all three on, it shorts the alternator and there\'s no output
from the bridge. The fet sources can be grounded, so the single gate
driver is easy. That\'s fairly clever.

Here\'s my FADEC regulator simulator.

https://www.dropbox.com/sh/x0h36owhyffn2gp/AADcj-TZYgkYsc-TSdBSRyyia?dl=0

I inherited the proto board, so it\'s not up to my usual gold standard
of Dremel\'d things.

I took out the previous fast gate drivers and added series gate
resistors and caps to slow down switching and bypass things better.
And bent the metal to bolt everything to.

The phase A current waveform, blue trace, kinda threw me, but it\'s
right. Yellow is the phase A voltage monitor. Both are picked off by
isolated delta-sigma ADCs.

 

[M Philbrook]

In article <8nq8if153h9ivuqtpeobrg2v3foir3ou4b@4ax.com>,
jlarkin@highland_atwork_technology.com says...

I always thought MOVs were sloppy, but they are actually pretty cool.

https://www.dropbox.com/s/9axwbhmmnd460n5/Littlefuse_V25S150P_EI.jpg?raw=1

We blew up a channel in our alternator simulator, probably some crazy
flyback voltage from the simulated load, so I\'m going to add an MOV
across each of the output phases. This one can absorb 22,000 amps and
300 joules.

390 volts max at 100 amps.

The low part of the curve looks very exponential. Someone once sold a
MOV type part as an analog computing element.

I work with big power at times and if that is truely an alternator
(Hardware rotor etc) Then you must be removing loads during critical
cycle times where as the regulator does not have a chance to redcuce the
field..

Alternators are current devices so removing the load abruptly is going
to produce some interesting results if the field was energized at some
higher levl.

Our run of the mill generator had such issues with the way we were
using it. It would at times cause a little damage to Mov\'s, fuses for
small devices when a large load was removed.

The fix was to figure out the L of the generator output, I used a meter
for that and then put some AC caps of good amp service across the
output. Using Welding caps are good for this, they should be low ESR
types.

But the results are the caps will absorb the sudden fly back effects
which is really an effect of unloading the alternator abruptly.

It isn\'t the best but but its better than nothing.