Photovoltaic inverter question

[Daku]

I have a photovoltaic inverter related
question. Recently I have been looking
into the possibility of building a grid-tie photovoltaic inverter. A
number of semiconductor vendors e.g., Freescale,
TI etc., sell controller kitss that have
built-in pulse width modulation units etc.,
to process the DC input from the solar
panel, using Maximum Power Point
Tracking and all.
What seems to be missing, is how to synchronize with the phase of the
grid.
One would imagine that the power grid
would tapped and the isolated input
fed into a phase locked loop to synchronize
with the grid supply phase. One cannot
inject power into the grid without phase
match.
Am I missing some subtle point ? Any
hints, suggestions would be of immense
help.

 

[Markus Hamilton]

On 6/19/2010 12:25, Daku wrote:

I have a photovoltaic inverter related
question. Recently I have been looking
into the possibility of building a grid-tie photovoltaic inverter. A
number of semiconductor vendors e.g., Freescale,
TI etc., sell controller kitss that have
built-in pulse width modulation units etc.,
to process the DC input from the solar
panel, using Maximum Power Point
Tracking and all.
What seems to be missing, is how to synchronize with the phase of the
grid.
One would imagine that the power grid
would tapped and the isolated input
fed into a phase locked loop to synchronize
with the grid supply phase. One cannot
inject power into the grid without phase
match.
Am I missing some subtle point ? Any
hints, suggestions would be of immense
help.

What you need to use are inverters which sync to the grid. You might
want to take a look here: http://www.enphaseenergy.com/
These inverters sync the generated AC to the grid AC, so that you can
feed back to the grid. However, when the grid fails, these inverters
usually shut down for 2 simple reasons:
(1) there is no reference anymore to sync the phase
(2) the inverters would immediately be overloaded

You might also want to check this site: http://www.builditsolar.com/

Markus

 

[John Larkin]

On Sat, 19 Jun 2010 09:25:38 -0700 (PDT), Daku <dakupoto@gmail.com>
wrote:

I have a photovoltaic inverter related
question. Recently I have been looking
into the possibility of building a grid-tie photovoltaic inverter. A
number of semiconductor vendors e.g., Freescale,
TI etc., sell controller kitss that have
built-in pulse width modulation units etc.,
to process the DC input from the solar
panel, using Maximum Power Point
Tracking and all.
What seems to be missing, is how to synchronize with the phase of the
grid.
One would imagine that the power grid
would tapped and the isolated input
fed into a phase locked loop to synchronize
with the grid supply phase. One cannot
inject power into the grid without phase
match.
Am I missing some subtle point ? Any
hints, suggestions would be of immense
help.

Yes, you'd have to sense the line voltage to sync to it, and probably
the inverter-line current.

You could do what the PFC power supply chips do, namely sense the AC
line voltage waveform in real time and make a boost converter's output
current track that. A slow control loop wraps around all that to get
the average, in this case optimum, power transfer. Maybe you could use
one of the PFC controller chips; they're cheap.

The problem is basically to present a negative resistance to the AC
power line.

Get anything wrong and it goes boom. Expect a shoe box full of
exploded fets if you do this from scratch. Wear eye protection.

ftp://jjlarkin.lmi.net/ExFets.jpg

John

 

[Bill Bowden]

On Jun 19, 9:25 am, Daku <dakup...@gmail.com> wrote:

I have a photovoltaic inverter related
question. Recently I have been looking
into the possibility of building a grid-tie photovoltaic inverter. A
number of semiconductor vendors e.g., Freescale,
TI etc., sell controller kitss that have
built-in pulse width modulation units etc.,
to process the DC input from the solar
panel, using Maximum Power Point
Tracking and all.
What seems to be missing, is how to synchronize with the phase of the
grid.
One would imagine that the power grid
would tapped and the isolated input
fed into a phase locked loop to synchronize
with the grid supply phase. One cannot
inject power into the grid without phase
match.
Am I missing some subtle point ? Any
hints, suggestions would be of immense
help.

There seems to be several "grid tie" inverters for sale on ebay.
Here's a 300 watt unit for $50. But only 37 minutes left on the
auction, so it might be gone now.

http://cgi.ebay.com/NEW-300w-GRID-TIE-INVERTER-12v-110v-solar-panel-/120584677361?cmd=ViewItem&pt=LH_DefaultDomain_0&hash=item1c136827f1


300W GRID TIE INVERTER,
for solar/wind panel use
12V/110V

feature:
1. power jack grid tie inverter is designed for small solar panel &
wind energy market, it's suitable for family enengy system.

2. this inverter can directly use solar panel, wind charger through
inverter to home grid.

3. easy to installation, just need solar panel, grid tie inverter,
then directly can put into home grid.

note: this inverter only has grid tie inverter function, do not have
tranditional inverter function, pls do not connect the battery for 12v
dc source, for further questions, pls leave message to ask, tks.

1.idea for power jack

The inverter can be connected to any outlet at home, when this line
run by the conventional electric network. The inverter IC will
monitors the volume, frequency and phase of the home grid, then
produce a pure sine wave that the frequency and phase will be match
the grid's, and the volume will be higher than the grid's, then
according to our current controlled PWM, to control the output power
to the grid. The inverter will puts out power when the home grid is
on.

2. why use power jack grid tie inverter?
when you use solar panel through grid tie inverter, your home power
meter will reduce the speed(if you are using other electric
appliances), or your home power meter will backward(if you are not use
any appliances)

3. difference of power jack grid tie inverter
traditional grid tie inverter is the solar panel are connect in
series, so if one solar panel did not work or bad efficiency, then the
whole system will be effects, but power jack grid tie inverter, you
can use every inverter in parallel, in this moment, each inverter has
it's own MPPT, can make every solar panel got the max power.

4. island protection

power jack grid tie inverter has 3greens light, when the charge
fucntion is normal, then this 3lights will turn on, but if there are
not dc sources(like in the night, no sun shine or raining day), the
red led light will turn on, the inverter will stop to work, in this
moment, the inverter will close the door, the home grid power will not
back to inverter.

Brand
Power Jack
Model No. PSWGT-300

Continuous Output Power

300W

Output Wave Form PURE SINE WAVE

DC Input Voltage

DC 14 Volt – 28Volt(solar panel)

AC Output Voltage AC 95v-130v

Frequency 50Hz-60Hz

Efficiency 90%

Distortion 2%

Temperature Protection 55C ą 5

Net Weight 2.0 kg

 

[Phil Allison]

"Cydrome Leader"

I had a hard time recently locating a specific power transistor in a
TO-218 case, with the metal tab and not the lump of plastic with a metal
back like everything seems to be now.

** Why bother ??

TO-218 is virtually the same pak and construction as TO-3P except you no
longer need to use an insulating bush with the latter.

TO-3 is a whole nuther animal with many advantages over plastic paks.


..... Phil

 

[Cydrome Leader]

John Larkin <jjlarkin@highnotlandthistechnologypart.com> wrote:

On Sat, 19 Jun 2010 09:25:38 -0700 (PDT), Daku <dakupoto@gmail.com
wrote:

I have a photovoltaic inverter related
question. Recently I have been looking
into the possibility of building a grid-tie photovoltaic inverter. A
number of semiconductor vendors e.g., Freescale,
TI etc., sell controller kitss that have
built-in pulse width modulation units etc.,
to process the DC input from the solar
panel, using Maximum Power Point
Tracking and all.
What seems to be missing, is how to synchronize with the phase of the
grid.
One would imagine that the power grid
would tapped and the isolated input
fed into a phase locked loop to synchronize
with the grid supply phase. One cannot
inject power into the grid without phase
match.
Am I missing some subtle point ? Any
hints, suggestions would be of immense
help.

Yes, you'd have to sense the line voltage to sync to it, and probably
the inverter-line current.

You could do what the PFC power supply chips do, namely sense the AC
line voltage waveform in real time and make a boost converter's output
current track that. A slow control loop wraps around all that to get
the average, in this case optimum, power transfer. Maybe you could use
one of the PFC controller chips; they're cheap.

The problem is basically to present a negative resistance to the AC
power line.

Get anything wrong and it goes boom. Expect a shoe box full of
exploded fets if you do this from scratch. Wear eye protection.

ftp://jjlarkin.lmi.net/ExFets.jpg

What was the case style of the very bottom left "exfet"?

I had a hard time recently locating a specific power transistor in a
TO-218 case, with the metal tab and not the lump of plastic with a metal
back like everything seems to be now.

I suspect people using TO-3s felt the same way when the TO-218s came out.

 

[Daku]

Dear Sir,
I have considered using PFCs before, but there is one point that is
not very clear. The scheme you suggest is that the PFC senses the grid
line, and forces the boost converter(input DC from solar panel) output
current synchronize with the grid AC voltage - am I right ? So then
comes the actual inverter. In this case who is supplying the PWM unit
with its high frequency carrier and low frequency modulation signal. I
guess the grid AC voltage could serve as the low frequency modulation
signal ?? Maybe I am thinking too much in analog terms.

On Jun 19, 11:41 pm, John Larkin
<jjlar...@highNOTlandTHIStechnologyPART.com> wrote:

Yes, you'd have to sense the line voltage to sync to it, and probably
the inverter-line current.

You could do what the PFC power supply chips do, namely sense the AC
line voltage waveform in real time and make a boost converter's output
current track that. A slow control loop wraps around all that to get
the average, in this case optimum, power transfer. Maybe you could use
one of the PFC controller chips; they're cheap.

The problem is basically to present a negative resistance to the AC
power line.

Get anything wrong and it goes boom. Expect a shoe box full of
exploded fets if you do this from scratch. Wear eye protection.

ftp://jjlarkin.lmi.net/ExFets.jpg

John

 

[Cydrome Leader]

Phil Allison <phil_a@tpg.com.au> wrote:

"Cydrome Leader"


I had a hard time recently locating a specific power transistor in a
TO-218 case, with the metal tab and not the lump of plastic with a metal
back like everything seems to be now.


** Why bother ??

TO-218 is virtually the same pak and construction as TO-3P except you no
longer need to use an insulating bush with the latter.

to not have to modify existing heatsink clamps. The setup in the product
was a bit weird with a clamp holding the metal tab onto the heatsink. I'm
not sure why the transistor wasn't just screwed down. There was a screw
and nut for the clamp anyways.

TO-3 is a whole nuther animal with many advantages over plastic paks.

the TO-218 is actually somewhat compatible with the TO-3.

If you have an old SK or EGC cross book you might find a section where
they show you how to wire the only available replacements for some TO-3
transistors using the TO-218 package.

If the original setup didn't use sockets, it wasn't a big deal.

 

[John Larkin]

On Sun, 20 Jun 2010 09:30:06 -0700 (PDT), Daku <dakupoto@gmail.com>
wrote:

Dear Sir,
I have considered using PFCs before, but there is one point that is
not very clear. The scheme you suggest is that the PFC senses the grid
line, and forces the boost converter(input DC from solar panel) output
current synchronize with the grid AC voltage - am I right ? So then
comes the actual inverter. In this case who is supplying the PWM unit
with its high frequency carrier and low frequency modulation signal. I
guess the grid AC voltage could serve as the low frequency modulation
signal ?? Maybe I am thinking too much in analog terms.

The HF carrier is any old oscillator. The modulation signal (which
controls boost converter duty cycle in a PFC-type power supply) is
created by analog-multiplying the line voltage waveform by a loop
error signal. It would probably be easier, nowadays, to do all this
digitally, in a little PIC or ARM or something.

Look up some PFC power supply control chip datasheets and appnotes.
It's a similar, or sort of reverse, problem.

John

 

[Phil Allison]

"Cydrome Leader"

Phil Allison
"Cydrome Leader"

I had a hard time recently locating a specific power transistor in a
TO-218 case, with the metal tab and not the lump of plastic with a metal
back like everything seems to be now.


** Why bother ??

TO-218 is virtually the same pak and construction as TO-3P except you no
longer need to use an insulating bush with the latter.

to not have to modify existing heatsink clamps. The setup in the product
was a bit weird with a clamp holding the metal tab onto the heatsink. I'm
not sure why the transistor wasn't just screwed down. There was a screw
and nut for the clamp anyways.

** A well designed clamp does a far better job with TO-3P and similar single
hole packs than using a bolt does. Normally the clamp supplies high pressure
along the CENTRE line of the plastic body of the device. The body spreads
the pressure evenly over the tab and there is then no tendency for it to
lift up at the lead end as there is with a bolt.

TO-3 is a whole nuther animal with many advantages over plastic paks.

the TO-218 is actually somewhat compatible with the TO-3.

** The main advantage of the TO3 pak is that there is no plastic in contact
with the chip which sits in a hermetically sealed environment - means
chips have a much longer service life even when running near max temps.

Internal feed wires can be sized to fuse immediately if a device fails - a
valuable feature not seen in plastic paks.

Two bolt mounting is easy to get right - long as you avoid those soft
plastic ( Nylon ? ) insulating bushes that crush under heat and pressure.


..... Phil

 

[Cydrome Leader]

Phil Allison <phil_a@tpg.com.au> wrote:

"Cydrome Leader"
Phil Allison
"Cydrome Leader"

I had a hard time recently locating a specific power transistor in a
TO-218 case, with the metal tab and not the lump of plastic with a metal
back like everything seems to be now.


** Why bother ??

TO-218 is virtually the same pak and construction as TO-3P except you no
longer need to use an insulating bush with the latter.

to not have to modify existing heatsink clamps. The setup in the product
was a bit weird with a clamp holding the metal tab onto the heatsink. I'm
not sure why the transistor wasn't just screwed down. There was a screw
and nut for the clamp anyways.

** A well designed clamp does a far better job with TO-3P and similar single
hole packs than using a bolt does. Normally the clamp supplies high pressure
along the CENTRE line of the plastic body of the device. The body spreads
the pressure evenly over the tab and there is then no tendency for it to
lift up at the lead end as there is with a bolt.


TO-3 is a whole nuther animal with many advantages over plastic paks.

the TO-218 is actually somewhat compatible with the TO-3.

** The main advantage of the TO3 pak is that there is no plastic in contact
with the chip which sits in a hermetically sealed environment - means
chips have a much longer service life even when running near max temps.

I'm not arguing that a TO-3 is better all around- it's just that fewer and
fewer semiconductors are packaged as nicely these days so that's what you
have to work with most of the time. The hermetically sealed and welded
metal can obviously costs more than some plastic resin molded around a
sliver of metal.

Sanken uses to have the most exciting TO-3 cases. The base was
surprisingly thick and they felt like they were made of gold.

Internal feed wires can be sized to fuse immediately if a device fails - a
valuable feature not seen in plastic paks.

But the plastic ones explode and burn.

Two bolt mounting is easy to get right - long as you avoid those soft
plastic ( Nylon ? ) insulating bushes that crush under heat and pressure.

I think they were a glass filled plastic. I may still have some mounting
kits with the mica washer, nuts, washer and lug.

I've seen lots of power supplies now have the power semiconductors glued
to the heatsinks, or the thermal pad is sort of like a really hard two
sided tape. I can't figure out if there is any repair method for that type
of stuff.

 

[John Fields]

On Mon, 21 Jun 2010 15:50:07 +0000 (UTC), Cydrome Leader
<presence@MUNGEpanix.com> wrote:

Phil Allison <phil_a@tpg.com.au> wrote:

"Cydrome Leader"
Phil Allison
"Cydrome Leader"

I had a hard time recently locating a specific power transistor in a
TO-218 case, with the metal tab and not the lump of plastic with a metal
back like everything seems to be now.


** Why bother ??

TO-218 is virtually the same pak and construction as TO-3P except you no
longer need to use an insulating bush with the latter.

to not have to modify existing heatsink clamps. The setup in the product
was a bit weird with a clamp holding the metal tab onto the heatsink. I'm
not sure why the transistor wasn't just screwed down. There was a screw
and nut for the clamp anyways.

** A well designed clamp does a far better job with TO-3P and similar single
hole packs than using a bolt does. Normally the clamp supplies high pressure
along the CENTRE line of the plastic body of the device. The body spreads
the pressure evenly over the tab and there is then no tendency for it to
lift up at the lead end as there is with a bolt.


TO-3 is a whole nuther animal with many advantages over plastic paks.

the TO-218 is actually somewhat compatible with the TO-3.

** The main advantage of the TO3 pak is that there is no plastic in contact
with the chip which sits in a hermetically sealed environment - means
chips have a much longer service life even when running near max temps.

I'm not arguing that a TO-3 is better all around- it's just that fewer and
fewer semiconductors are packaged as nicely these days so that's what you
have to work with most of the time. The hermetically sealed and welded
metal can obviously costs more than some plastic resin molded around a
sliver of metal.

Sanken uses to have the most exciting TO-3 cases. The base was
surprisingly thick and they felt like they were made of gold.

Internal feed wires can be sized to fuse immediately if a device fails - a
valuable feature not seen in plastic paks.

But the plastic ones explode and burn.

Two bolt mounting is easy to get right - long as you avoid those soft
plastic ( Nylon ? ) insulating bushes that crush under heat and pressure.

I think they were a glass filled plastic. I may still have some mounting
kits with the mica washer, nuts, washer and lug.

---
They're in the present tense, actually, and available in Nylon and
glass-filled polyphenylene sulfide.
---

I've seen lots of power supplies now have the power semiconductors glued
to the heatsinks, or the thermal pad is sort of like a really hard two
sided tape. I can't figure out if there is any repair method for that type
of stuff.

---
http://www.braceface.com/medical/Surgery_set_images/CW_instruments_images/Bone%20hammer%20and%20chisel.JPG

 

[krw@att.bizzzzzzzzzzzz]

On Mon, 21 Jun 2010 15:50:07 +0000 (UTC), Cydrome Leader
<presence@MUNGEpanix.com> wrote:

Phil Allison <phil_a@tpg.com.au> wrote:

"Cydrome Leader"
Phil Allison
"Cydrome Leader"

I had a hard time recently locating a specific power transistor in a
TO-218 case, with the metal tab and not the lump of plastic with a metal
back like everything seems to be now.


** Why bother ??

TO-218 is virtually the same pak and construction as TO-3P except you no
longer need to use an insulating bush with the latter.

to not have to modify existing heatsink clamps. The setup in the product
was a bit weird with a clamp holding the metal tab onto the heatsink. I'm
not sure why the transistor wasn't just screwed down. There was a screw
and nut for the clamp anyways.

** A well designed clamp does a far better job with TO-3P and similar single
hole packs than using a bolt does. Normally the clamp supplies high pressure
along the CENTRE line of the plastic body of the device. The body spreads
the pressure evenly over the tab and there is then no tendency for it to
lift up at the lead end as there is with a bolt.


TO-3 is a whole nuther animal with many advantages over plastic paks.

the TO-218 is actually somewhat compatible with the TO-3.

** The main advantage of the TO3 pak is that there is no plastic in contact
with the chip which sits in a hermetically sealed environment - means
chips have a much longer service life even when running near max temps.

I'm not arguing that a TO-3 is better all around- it's just that fewer and
fewer semiconductors are packaged as nicely these days so that's what you
have to work with most of the time. The hermetically sealed and welded
metal can obviously costs more than some plastic resin molded around a
sliver of metal.

Sanken uses to have the most exciting TO-3 cases. The base was
surprisingly thick and they felt like they were made of gold.

Internal feed wires can be sized to fuse immediately if a device fails - a
valuable feature not seen in plastic paks.

But the plastic ones explode and burn.

Metal ones can explode and throw shrapnel around the room.

Two bolt mounting is easy to get right - long as you avoid those soft
plastic ( Nylon ? ) insulating bushes that crush under heat and pressure.

I think they were a glass filled plastic. I may still have some mounting
kits with the mica washer, nuts, washer and lug.

I've seen lots of power supplies now have the power semiconductors glued
to the heatsinks, or the thermal pad is sort of like a really hard two
sided tape. I can't figure out if there is any repair method for that type
of stuff.

Thermal pads are really crappy.

 

[JW]

On Mon, 21 Jun 2010 17:42:21 -0500 "krw@att.bizzzzzzzzzzzz"
<krw@att.bizzzzzzzzzzzz> wrote in Message id:
<iiqv1650144gv9gu9kju00tl8ec8abqlau@4ax.com>:

On Mon, 21 Jun 2010 15:50:07 +0000 (UTC), Cydrome Leader
presence@MUNGEpanix.com> wrote:

Phil Allison <phil_a@tpg.com.au> wrote:

"Cydrome Leader"
Phil Allison
"Cydrome Leader"

I had a hard time recently locating a specific power transistor in a
TO-218 case, with the metal tab and not the lump of plastic with a metal
back like everything seems to be now.


** Why bother ??

TO-218 is virtually the same pak and construction as TO-3P except you no
longer need to use an insulating bush with the latter.

to not have to modify existing heatsink clamps. The setup in the product
was a bit weird with a clamp holding the metal tab onto the heatsink. I'm
not sure why the transistor wasn't just screwed down. There was a screw
and nut for the clamp anyways. JW: Cue AlwaysWrong!

** A well designed clamp does a far better job with TO-3P and similar single
hole packs than using a bolt does. Normally the clamp supplies high pressure
along the CENTRE line of the plastic body of the device. The body spreads
the pressure evenly over the tab and there is then no tendency for it to
lift up at the lead end as there is with a bolt.


TO-3 is a whole nuther animal with many advantages over plastic paks.

the TO-218 is actually somewhat compatible with the TO-3.

** The main advantage of the TO3 pak is that there is no plastic in contact
with the chip which sits in a hermetically sealed environment - means
chips have a much longer service life even when running near max temps.

I'm not arguing that a TO-3 is better all around- it's just that fewer and
fewer semiconductors are packaged as nicely these days so that's what you
have to work with most of the time. The hermetically sealed and welded
metal can obviously costs more than some plastic resin molded around a
sliver of metal.

Sanken uses to have the most exciting TO-3 cases. The base was
surprisingly thick and they felt like they were made of gold.

Internal feed wires can be sized to fuse immediately if a device fails - a
valuable feature not seen in plastic paks.

But the plastic ones explode and burn.

Metal ones can explode and throw shrapnel around the room.

A TO-3 explode? I've *never* seen that happen, and hope I never do!

 

[Cydrome Leader]

JW <none@dev.null> wrote:

On Mon, 21 Jun 2010 17:42:21 -0500 "krw@att.bizzzzzzzzzzzz"
krw@att.bizzzzzzzzzzzz> wrote in Message id:
iiqv1650144gv9gu9kju00tl8ec8abqlau@4ax.com>:

On Mon, 21 Jun 2010 15:50:07 +0000 (UTC), Cydrome Leader
presence@MUNGEpanix.com> wrote:

Phil Allison <phil_a@tpg.com.au> wrote:

"Cydrome Leader"
Phil Allison
"Cydrome Leader"

I had a hard time recently locating a specific power transistor in a
TO-218 case, with the metal tab and not the lump of plastic with a metal
back like everything seems to be now.


** Why bother ??

TO-218 is virtually the same pak and construction as TO-3P except you no
longer need to use an insulating bush with the latter.

to not have to modify existing heatsink clamps. The setup in the product
was a bit weird with a clamp holding the metal tab onto the heatsink. I'm
not sure why the transistor wasn't just screwed down. There was a screw
and nut for the clamp anyways. JW: Cue AlwaysWrong!

** A well designed clamp does a far better job with TO-3P and similar single
hole packs than using a bolt does. Normally the clamp supplies high pressure
along the CENTRE line of the plastic body of the device. The body spreads
the pressure evenly over the tab and there is then no tendency for it to
lift up at the lead end as there is with a bolt.


TO-3 is a whole nuther animal with many advantages over plastic paks.

the TO-218 is actually somewhat compatible with the TO-3.

** The main advantage of the TO3 pak is that there is no plastic in contact
with the chip which sits in a hermetically sealed environment - means
chips have a much longer service life even when running near max temps.

I'm not arguing that a TO-3 is better all around- it's just that fewer and
fewer semiconductors are packaged as nicely these days so that's what you
have to work with most of the time. The hermetically sealed and welded
metal can obviously costs more than some plastic resin molded around a
sliver of metal.

Sanken uses to have the most exciting TO-3 cases. The base was
surprisingly thick and they felt like they were made of gold.

Internal feed wires can be sized to fuse immediately if a device fails - a
valuable feature not seen in plastic paks.

But the plastic ones explode and burn.

Metal ones can explode and throw shrapnel around the room.

A TO-3 explode? I've *never* seen that happen, and hope I never do!

I've not seen or heard of it, but never worked with high power stuff and
to-3 cans.

The fist sized plastic shrouded mosfets or IGBTs they use in large online
UPS explode though, and splash what seems to be silicone gel all over the
place. That's not counting the sooty fire that usually happens at the same
time.

 

[krw@att.bizzzzzzzzzzzz]

On Tue, 22 Jun 2010 05:56:43 -0400, JW <none@dev.null> wrote:

On Mon, 21 Jun 2010 17:42:21 -0500 "krw@att.bizzzzzzzzzzzz"
krw@att.bizzzzzzzzzzzz> wrote in Message id:
iiqv1650144gv9gu9kju00tl8ec8abqlau@4ax.com>:

On Mon, 21 Jun 2010 15:50:07 +0000 (UTC), Cydrome Leader
presence@MUNGEpanix.com> wrote:

Phil Allison <phil_a@tpg.com.au> wrote:

"Cydrome Leader"
Phil Allison
"Cydrome Leader"

I had a hard time recently locating a specific power transistor in a
TO-218 case, with the metal tab and not the lump of plastic with a metal
back like everything seems to be now.


** Why bother ??

TO-218 is virtually the same pak and construction as TO-3P except you no
longer need to use an insulating bush with the latter.

to not have to modify existing heatsink clamps. The setup in the product
was a bit weird with a clamp holding the metal tab onto the heatsink. I'm
not sure why the transistor wasn't just screwed down. There was a screw
and nut for the clamp anyways. JW: Cue AlwaysWrong!

** A well designed clamp does a far better job with TO-3P and similar single
hole packs than using a bolt does. Normally the clamp supplies high pressure
along the CENTRE line of the plastic body of the device. The body spreads
the pressure evenly over the tab and there is then no tendency for it to
lift up at the lead end as there is with a bolt.


TO-3 is a whole nuther animal with many advantages over plastic paks.

the TO-218 is actually somewhat compatible with the TO-3.

** The main advantage of the TO3 pak is that there is no plastic in contact
with the chip which sits in a hermetically sealed environment - means
chips have a much longer service life even when running near max temps.

I'm not arguing that a TO-3 is better all around- it's just that fewer and
fewer semiconductors are packaged as nicely these days so that's what you
have to work with most of the time. The hermetically sealed and welded
metal can obviously costs more than some plastic resin molded around a
sliver of metal.

Sanken uses to have the most exciting TO-3 cases. The base was
surprisingly thick and they felt like they were made of gold.

Internal feed wires can be sized to fuse immediately if a device fails - a
valuable feature not seen in plastic paks.

But the plastic ones explode and burn.

Metal ones can explode and throw shrapnel around the room.

A TO-3 explode? I've *never* seen that happen, and hope I never do!

Yep. One failure mode the base lead came *though* the case like a bullet. In
another the whole top of the case came off and ricocheted around the room.
They ended up putting the power supplies in a bullet-proof test chamber for
their christening. Secondary breakdown can be an impressive event.

 

[baron]

krw@att.bizzzzzzzzzzzz Inscribed thus:

On Tue, 22 Jun 2010 05:56:43 -0400, JW <none@dev.null> wrote:

On Mon, 21 Jun 2010 17:42:21 -0500 "krw@att.bizzzzzzzzzzzz"
krw@att.bizzzzzzzzzzzz> wrote in Message id:
iiqv1650144gv9gu9kju00tl8ec8abqlau@4ax.com>:

On Mon, 21 Jun 2010 15:50:07 +0000 (UTC), Cydrome Leader
presence@MUNGEpanix.com> wrote:

Phil Allison <phil_a@tpg.com.au> wrote:

"Cydrome Leader"
Phil Allison
"Cydrome Leader"

I had a hard time recently locating a specific power transistor
in a TO-218 case, with the metal tab and not the lump of
plastic with a metal back like everything seems to be now.


** Why bother ??

TO-218 is virtually the same pak and construction as TO-3P
except you no longer need to use an insulating bush with the
latter.

to not have to modify existing heatsink clamps. The setup in the
product was a bit weird with a clamp holding the metal tab onto
the heatsink. I'm not sure why the transistor wasn't just screwed
down. There was a screw and nut for the clamp anyways. JW: Cue
AlwaysWrong!

** A well designed clamp does a far better job with TO-3P and
similar single hole packs than using a bolt does. Normally the
clamp supplies high pressure
along the CENTRE line of the plastic body of the device. The body
spreads the pressure evenly over the tab and there is then no
tendency for it to lift up at the lead end as there is with a
bolt.


TO-3 is a whole nuther animal with many advantages over plastic
paks.

the TO-218 is actually somewhat compatible with the TO-3.

** The main advantage of the TO3 pak is that there is no plastic
in contact
with the chip which sits in a hermetically sealed environment -
means chips have a much longer service life even when running near
max temps.

I'm not arguing that a TO-3 is better all around- it's just that
fewer and fewer semiconductors are packaged as nicely these days so
that's what you have to work with most of the time. The hermetically
sealed and welded metal can obviously costs more than some plastic
resin molded around a sliver of metal.

Sanken uses to have the most exciting TO-3 cases. The base was
surprisingly thick and they felt like they were made of gold.

Internal feed wires can be sized to fuse immediately if a device
fails - a valuable feature not seen in plastic paks.

But the plastic ones explode and burn.

Metal ones can explode and throw shrapnel around the room.

A TO-3 explode? I've *never* seen that happen, and hope I never do!

Yep. One failure mode the base lead came *though* the case like a
bullet. In another the whole top of the case came off and ricocheted
around the room. They ended up putting the power supplies in a
bullet-proof test chamber for
their christening. Secondary breakdown can be an impressive event.

I've had 3771's go bang and lift the top hat, but never blow it off
compleatly.

--
Best Regards:
Baron.