Delta vs Y arrangement for 3-terminal transient voltage supp

[Tim Shoppa]

When I open the catalogs I see both "Y" and "Delta" arrangements
for three-terminal TVS's. But I'm not entirely clear on where each
arrangement is most appropriate. My random thoughts:

The Y has two suppresors in series between any two terminals. Putting
them in series, I suppose, reduces capacitance, which may be important
at higher frequencies. But it also seems to double the impedance to
shunt a HV pulse.

The Delta seems to be better
at clipping lower voltages because you don't have to put two elements
in series.

But there must be something I'm missing here as to which is best used where.

My current application is rather low voltage (3.3V differential pair) at
moderate rates (a few Mbits) and it seems that the Delta configuration is
the best match.

Tim.

 

[Rich Grise]

"Tim Shoppa" <shoppa@trailing-edge.com> wrote in message
news:bec993c8.0405050842.3ea024b2@posting.google.com...

When I open the catalogs I see both "Y" and "Delta" arrangements
for three-terminal TVS's. But I'm not entirely clear on where each
arrangement is most appropriate. My random thoughts:

The Y has two suppresors in series between any two terminals. Putting
them in series, I suppose, reduces capacitance, which may be important
at higher frequencies. But it also seems to double the impedance to
shunt a HV pulse.

The Delta seems to be better
at clipping lower voltages because you don't have to put two elements
in series.

But there must be something I'm missing here as to which is best used
where.

My current application is rather low voltage (3.3V differential pair) at
moderate rates (a few Mbits) and it seems that the Delta configuration is
the best match.

Tim.

The first thing that you're missing is that the TVS's you're looking at
are for three-phase mains. The Y and Delta are two common connection
configurations - it's probably pretty easy to look up an explanation
for them, but I'm almost confident that the parts you're looking at are
not at all suitable for the app you're talking about. That's the
kind of deal where I'd put reverse-biased signal diodes between the
line(s) and Vss and line(s) and Vdd (or Vee/Vcc, or ground and +V,
or however you're calling it out. i.e.:


+3.3Vcc
|
k -
^ Diode
|
--------+-------- signal
|
k -
^ Diode
|
Gnd

Hope This Helps!
Rich

 

[Jim Adney]

On Wed, 05 May 2004 17:59:54 GMT "Rich Grise" <null@example.net>
wrote:

The first thing that you're missing is that the TVS's you're looking at
are for three-phase mains.

Maybe, but why would there be a THREE terminal Y configuration?

A 3-phase Y system would need a 4th terminal.

-
-----------------------------------------------
Jim Adney jadney@vwtype3.org
Madison, WI 53711 USA
-----------------------------------------------

 

[Peter A Forbes]

On 5 May 2004 09:42:27 -0700, shoppa@trailing-edge.com (Tim Shoppa) wrote:

When I open the catalogs I see both "Y" and "Delta" arrangements
for three-terminal TVS's. But I'm not entirely clear on where each
arrangement is most appropriate. My random thoughts:

As has already been explained by others, the Delta and Star (Y or Wye)
connection arrangements originate from 3-phase power supplies and consumers like
motors etc.

Delta is normally used for machinery supplies where a neutral is not needed,
similarly for HV (11kV to 256kV) transmission purposes.

Star or Y or Wye is used at local distribution level where three-phase and
neutral can be used to extract (for example) 240V single phase from a 440V
phase-phase 3-phase and neutral supply. In the USA it is 110V from 208
phase-phase supply IIRC.

Transfomers usually have Delta input and Star output for phasing and harmonics
reasons. We have just taken delivery (yesterday) of a 100kVA 415/440V Delta
input to twin secondary 58V and 583V for a special battery charger. The neutral
point on the secondary goes unused as we feed the secondaries into fully
controlled thyristor bridges. Tranny is about 700kg or nearly 3/4 of a ton. With
the two smoothing chokes the inductors are about 850kg total.

Peter

--
Peter & Rita Forbes
diesel@easynet.co.uk
Engine pages for preservation info:
http://www.oldengine.org/members/diesel

 

[Tim Shoppa]

"Rich Grise" <null@example.net> wrote in message news:<uY9mc.88904$G_.27732@nwrddc02.gnilink.net>...

The first thing that you're missing is that the TVS's you're looking at
are for three-phase mains.

Nope, they aren't. When a manufacturer sells a 3-device sidactor network
that trips at 14V, it's not for mains power.

The Y and Delta are two common connection
configurations [for three-phase power]

Like everyone else, you're assuming that when I say "Delta" and "Wye"
that I'm talking about mains power, but I'm not. Those terms are
perfectly relevant for any connection of three devices to three terminals.

I suppose I would've had better success asking in a telecom-related
group about TVS's used in telco demarcs. When I ask about differential
Mbps-rate signal surge protection and everyone starts correcting me and
telling me I'm really asking about three-phase mains power, I must've asked
the question in the wrong place.

Tim.

 

[Rich Grise]

"Tim Shoppa" <shoppa@trailing-edge.com> wrote in message
news:bec993c8.0405060837.3c2e0805@posting.google.com...

"Rich Grise" <null@example.net> wrote in message
news:<uY9mc.88904$G_.27732@nwrddc02.gnilink.net>...

Like everyone else, you're assuming that when I say "Delta" and "Wye"
that I'm talking about mains power, but I'm not. Those terms are
perfectly relevant for any connection of three devices to three terminals.

I suppose I would've had better success asking in a telecom-related
group about TVS's used in telco demarcs. When I ask about differential
Mbps-rate signal surge protection and everyone starts correcting me and
telling me I'm really asking about three-phase mains power, I must've
asked
the question in the wrong place.

Sorry. I stand humbly corrected.

Thanks,
Rich

 

[Terry Given]

"Peter A Forbes" <diesel@easynet.co.uk> wrote in message
news:18rj905ict04i8h7k2nluvionr87kbmg3s@4ax.com...

On 5 May 2004 09:42:27 -0700, shoppa@trailing-edge.com (Tim Shoppa) wrote:

As has already been explained by others, the Delta and Star (Y or Wye)
connection arrangements originate from 3-phase power supplies and
consumers like
motors etc.

this is merely one application of star and delta connected networks. A "pi"
filter is a delta three-terminal network; conversely a "T" filter is a star.
The same transformations from star-to-delta and back again also apply to
filters. And any other suitable network and (IIRC) its dual....ultimately
its just network theory. And yes, it works at 50Hz, from mW to MW.....

Terry

 

[Tim Shoppa]

"Terry Given" <the_domes@xtra.co.nz> wrote in message news:<Fq0oc.3324$XI4.127413@news.xtra.co.nz>...

"Peter A Forbes" <diesel@easynet.co.uk> wrote in message
news:18rj905ict04i8h7k2nluvionr87kbmg3s@4ax.com...
On 5 May 2004 09:42:27 -0700, shoppa@trailing-edge.com (Tim Shoppa) wrote:

As has already been explained by others, the Delta and Star (Y or Wye)
connection arrangements originate from 3-phase power supplies and
consumers like
motors etc.

this is merely one application of star and delta connected networks. A "pi"
filter is a delta three-terminal network; conversely a "T" filter is a star.
The same transformations from star-to-delta and back again also apply to
filters. And any other suitable network and (IIRC) its dual....ultimately
its just network theory. And yes, it works at 50Hz, from mW to MW.....

Not to diss network theory, linear network theory is great stuff
.... but TVS's (Sidactors, MOV's, Gas discharge tubes,
etc.) are not linear devices when activated. They are quite nonlinear
and often exhibit hysteresis. I suspect that part of the reason for
preferring Y over Delta (or the other way around!) has something to do
with the nonlinear characteristics, but that's just a guess.

Tim.