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Aircraft Hypot Test
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Yzordderrex
Apr 27, 2017, 1:03:52 PM4/27/17
to
I am interested to know if there is a specification for dielectric withstand test for aircraft. I can't find anything concrete in DO-160. I know of Mil-std-202, and expect I can apply it to civilian aircraft.
I have a client that insists he does not have to hipot and I disagree. My gut tells me that any gear that is isolated from ground should be tested in some manner. I think good engineering practice would dictate a test.
The unit runs off of 120vac wild power. That is I think 360Hz - 800Hz. Don't quote me but on that but it is close. We have caps to ground so would go with the DC hypot.
My guess would be (2x120+1000)*2^0.5
Make sense?
regards,
Bob
I have a client that insists he does not have to hipot and I disagree. My gut tells me that any gear that is isolated from ground should be tested in some manner. I think good engineering practice would dictate a test.
The unit runs off of 120vac wild power. That is I think 360Hz - 800Hz. Don't quote me but on that but it is close. We have caps to ground so would go with the DC hypot.
My guess would be (2x120+1000)*2^0.5
Make sense?
regards,
Bob
rickman
Apr 27, 2017, 1:19:23 PM4/27/17
to
components.
What is the impact of a short to ground?
I'm not familiar with the term "wild power". Googling didn't help.
--
Rick C
dalai lamah
Apr 27, 2017, 1:45:43 PM4/27/17
to
Un bel giorno Yzordderrex digitň:
> I am interested to know if there is a specification for dielectric
> withstand test for aircraft. I can't find anything concrete in DO-160.
> I know of Mil-std-202, and expect I can apply it to civilian aircraft.
Yes, it is quite common to use the MIL-STD-202 method 301 and especially
method 302 (insulation resistance) also for civil aircrafts.
> I have a client that insists he does not have to hipot and I disagree.
> My gut tells me that any gear that is isolated from ground should be
> tested in some manner. I think good engineering practice would dictate a
> test.
It may be a good idea to make some measurements during the engineering
tests (just to spot design flaws), but if you don't have a customer
requirement that dictates it, I would avoid to mention it in your
specification. Each additional test requires additional time and money
during the qualification phase.
--
Fletto i muscoli e sono nel vuoto.
> I am interested to know if there is a specification for dielectric
> withstand test for aircraft. I can't find anything concrete in DO-160.
> I know of Mil-std-202, and expect I can apply it to civilian aircraft.
method 302 (insulation resistance) also for civil aircrafts.
> I have a client that insists he does not have to hipot and I disagree.
> My gut tells me that any gear that is isolated from ground should be
> tested in some manner. I think good engineering practice would dictate a
> test.
tests (just to spot design flaws), but if you don't have a customer
requirement that dictates it, I would avoid to mention it in your
specification. Each additional test requires additional time and money
during the qualification phase.
--
Fletto i muscoli e sono nel vuoto.
rickman
Apr 27, 2017, 2:32:31 PM4/27/17
to
On 4/27/2017 1:45 PM, dalai lamah wrote:
> Un bel giorno Yzordderrex digitò:
I believe his question is about the general safety requirement implying
a hipot test. Not everything about a design has to be explicitly stated
as a requirement.
--
Rick C
> Un bel giorno Yzordderrex digitò:
a hipot test. Not everything about a design has to be explicitly stated
as a requirement.
--
Rick C
Joerg
Apr 27, 2017, 2:48:47 PM4/27/17
to
called neutral in house wiring via the fuselage. That has always scared
me but it's often the way it is. Not in very large passenger aircraft
though with three-phase APUs and stuff.
If it is ground return via fuselage in your case there most likely will
only be the usual DO-160 surge and undervoltage requirements, frequency
range, EMC, et cetera.
--
Regards, Joerg
http://www.analogconsultants.com/
Tim Wescott
Apr 27, 2017, 3:07:21 PM4/27/17
to
(Sez the guy who's had to help puzzled street rodders figure out why
their instruments didn't work on their fiberglass dashboards...)
--
Tim Wescott
Wescott Design Services
http://www.wescottdesign.com
I'm looking for work -- see my website!
Joerg
Apr 27, 2017, 3:36:23 PM4/27/17
to
On 2017-04-27 12:07, Tim Wescott wrote:
> On Thu, 27 Apr 2017 11:48:52 -0700, Joerg wrote:
>
>> On 2017-04-27 10:03, Yzordderrex wrote:
>>> I am interested to know if there is a specification for dielectric
>>> withstand test for aircraft. I can't find anything concrete in DO-160.
>>> I know of Mil-std-202, and expect I can apply it to civilian aircraft.
>>>
>>> I have a client that insists he does not have to hipot and I disagree.
>>> My gut tells me that any gear that is isolated from ground should be
>>> tested in some manner. I think good engineering practice would dictate
>>> a test.
>>>
>>> The unit runs off of 120vac wild power. That is I think 360Hz - 800Hz.
>>> Don't quote me but on that but it is close. We have caps to ground so
>>> would go with the DC hypot.
>>>
>>> My guess would be (2x120+1000)*2^0.5
>>>
>>> Make sense?
>>>
>>>
>> In many cases aircraft power systems run the return or what would be
>> called neutral in house wiring via the fuselage. That has always scared
>> me but it's often the way it is. Not in very large passenger aircraft
>> though with three-phase APUs and stuff.
>>
>> If it is ground return via fuselage in your case there most likely will
>> only be the usual DO-160 surge and undervoltage requirements, frequency
>> range, EMC, et cetera.
>
> How does that work on fiberglass aircraft?
>
Reminds me of an EMC debug on an experimental pusher prop aircraft. We
> On Thu, 27 Apr 2017 11:48:52 -0700, Joerg wrote:
>
>> On 2017-04-27 10:03, Yzordderrex wrote:
>>> I am interested to know if there is a specification for dielectric
>>> withstand test for aircraft. I can't find anything concrete in DO-160.
>>> I know of Mil-std-202, and expect I can apply it to civilian aircraft.
>>>
>>> I have a client that insists he does not have to hipot and I disagree.
>>> My gut tells me that any gear that is isolated from ground should be
>>> tested in some manner. I think good engineering practice would dictate
>>> a test.
>>>
>>> The unit runs off of 120vac wild power. That is I think 360Hz - 800Hz.
>>> Don't quote me but on that but it is close. We have caps to ground so
>>> would go with the DC hypot.
>>>
>>> My guess would be (2x120+1000)*2^0.5
>>>
>>> Make sense?
>>>
>>>
>> In many cases aircraft power systems run the return or what would be
>> called neutral in house wiring via the fuselage. That has always scared
>> me but it's often the way it is. Not in very large passenger aircraft
>> though with three-phase APUs and stuff.
>>
>> If it is ground return via fuselage in your case there most likely will
>> only be the usual DO-160 surge and undervoltage requirements, frequency
>> range, EMC, et cetera.
>
> How does that work on fiberglass aircraft?
>
got it fixed and no more buzz and stuff on the radio. Didn't help
though, the test pilot landed half a mile short of the runway. It was a
weird design IMHO. The engine upfront, a looong shaft running underneath
the pilot seat to the rear where the prop was. On the way back, some
vibration under the seat, RPMs dropped, more vibration, RPMs dropped
some more, throttle all the way in .... rrrrat-tat-tat ... some clanging
... PHUT ... silence.
> (Sez the guy who's had to help puzzled street rodders figure out why
> their instruments didn't work on their fiberglass dashboards...)
>
who tied the ground lug under a screw. "But the manual says so!" ...
"Yeah, but the dash is foam and it screws into plastic inserts" ... "Oh".
Clifford Heath
Apr 27, 2017, 6:36:25 PM4/27/17
to
On 28/04/17 05:07, Tim Wescott wrote:
> On Thu, 27 Apr 2017 11:48:52 -0700, Joerg wrote:
>
>> On 2017-04-27 10:03, Yzordderrex wrote:
>>> I am interested to know if there is a specification for dielectric
>>> withstand test for aircraft. I can't find anything concrete in DO-160.
>>> I know of Mil-std-202, and expect I can apply it to civilian aircraft.
>>>
>>> I have a client that insists he does not have to hipot and I disagree.
>>> My gut tells me that any gear that is isolated from ground should be
>>> tested in some manner. I think good engineering practice would dictate
>>> a test.
>>>
>>> The unit runs off of 120vac wild power. That is I think 360Hz - 800Hz.
>>> Don't quote me but on that but it is close. We have caps to ground so
>>> would go with the DC hypot.
>>>
>>> My guess would be (2x120+1000)*2^0.5
>>>
>>> Make sense?
>>>
>>>
>> In many cases aircraft power systems run the return or what would be
>> called neutral in house wiring via the fuselage. That has always scared
>> me but it's often the way it is. Not in very large passenger aircraft
>> though with three-phase APUs and stuff.
>>
>> If it is ground return via fuselage in your case there most likely will
>> only be the usual DO-160 surge and undervoltage requirements, frequency
>> range, EMC, et cetera.
>
> How does that work on fiberglass aircraft?
Maybe that's why they thought carbon fibre would be an improvement?
> On Thu, 27 Apr 2017 11:48:52 -0700, Joerg wrote:
>
>> On 2017-04-27 10:03, Yzordderrex wrote:
>>> I am interested to know if there is a specification for dielectric
>>> withstand test for aircraft. I can't find anything concrete in DO-160.
>>> I know of Mil-std-202, and expect I can apply it to civilian aircraft.
>>>
>>> I have a client that insists he does not have to hipot and I disagree.
>>> My gut tells me that any gear that is isolated from ground should be
>>> tested in some manner. I think good engineering practice would dictate
>>> a test.
>>>
>>> The unit runs off of 120vac wild power. That is I think 360Hz - 800Hz.
>>> Don't quote me but on that but it is close. We have caps to ground so
>>> would go with the DC hypot.
>>>
>>> My guess would be (2x120+1000)*2^0.5
>>>
>>> Make sense?
>>>
>>>
>> In many cases aircraft power systems run the return or what would be
>> called neutral in house wiring via the fuselage. That has always scared
>> me but it's often the way it is. Not in very large passenger aircraft
>> though with three-phase APUs and stuff.
>>
>> If it is ground return via fuselage in your case there most likely will
>> only be the usual DO-160 surge and undervoltage requirements, frequency
>> range, EMC, et cetera.
>
> How does that work on fiberglass aircraft?
:)
Lasse Langwadt Christensen
Apr 27, 2017, 6:42:22 PM4/27/17
to
is an issue they had to consider when they started making aircrafts out of composites
k...@notreal.com
Apr 27, 2017, 9:00:34 PM4/27/17
to
Clive Arthur
Apr 28, 2017, 6:39:39 AM4/28/17
to
On 27/04/2017 18:19, rickman wrote:
> On 4/27/2017 1:03 PM, Yzordderrex wrote:
>> I am interested to know if there is a specification for dielectric
>> withstand test for aircraft. I can't find anything concrete in
>> DO-160. I know of Mil-std-202, and expect I can apply it to civilian
>> aircraft.
>>
>> I have a client that insists he does not have to hipot and I
>> disagree. My gut tells me that any gear that is isolated from ground
>> should be tested in some manner. I think good engineering practice
>> would dictate a test.
>>
>> The unit runs off of 120vac wild power. That is I think 360Hz -
>> 800Hz. Don't quote me but on that but it is close. We have caps to
>> ground so would go with the DC hypot.
>>
>> My guess would be (2x120+1000)*2^0.5
>>
>> Make sense?
>
> I believe military aircraft use 440 Hz to reduce the weight of magnetic
> components.
It's actually 400Hz in aircraft, the significance of 440Hz is that it's
> On 4/27/2017 1:03 PM, Yzordderrex wrote:
>> I am interested to know if there is a specification for dielectric
>> withstand test for aircraft. I can't find anything concrete in
>> DO-160. I know of Mil-std-202, and expect I can apply it to civilian
>> aircraft.
>>
>> I have a client that insists he does not have to hipot and I
>> disagree. My gut tells me that any gear that is isolated from ground
>> should be tested in some manner. I think good engineering practice
>> would dictate a test.
>>
>> The unit runs off of 120vac wild power. That is I think 360Hz -
>> 800Hz. Don't quote me but on that but it is close. We have caps to
>> ground so would go with the DC hypot.
>>
>> My guess would be (2x120+1000)*2^0.5
>>
>> Make sense?
>
> I believe military aircraft use 440 Hz to reduce the weight of magnetic
> components.
a standard for A above middle C.
> What is the impact of a short to ground?
>
> I'm not familiar with the term "wild power". Googling didn't help.
>
--
Clive
Spehro Pefhany
Apr 28, 2017, 8:00:24 AM4/28/17
to
On Thu, 27 Apr 2017 13:19:19 -0400, the renowned rickman
<gnu...@gmail.com> wrote:
>On 4/27/2017 1:03 PM, Yzordderrex wrote:
>> I am interested to know if there is a specification for dielectric withstand test for aircraft. I can't find anything concrete in DO-160. I know of Mil-std-202, and expect I can apply it to civilian aircraft.
>>
>> I have a client that insists he does not have to hipot and I disagree. My gut tells me that any gear that is isolated from ground should be tested in some manner. I think good engineering practice would dictate a test.
>>
>> The unit runs off of 120vac wild power. That is I think 360Hz - 800Hz. Don't quote me but on that but it is close. We have caps to ground so would go with the DC hypot.
>>
>> My guess would be (2x120+1000)*2^0.5
>>
>> Make sense?
>
>I believe military aircraft use 440 Hz to reduce the weight of magnetic
>components.
400Hz
<gnu...@gmail.com> wrote:
>On 4/27/2017 1:03 PM, Yzordderrex wrote:
>> I am interested to know if there is a specification for dielectric withstand test for aircraft. I can't find anything concrete in DO-160. I know of Mil-std-202, and expect I can apply it to civilian aircraft.
>>
>> I have a client that insists he does not have to hipot and I disagree. My gut tells me that any gear that is isolated from ground should be tested in some manner. I think good engineering practice would dictate a test.
>>
>> The unit runs off of 120vac wild power. That is I think 360Hz - 800Hz. Don't quote me but on that but it is close. We have caps to ground so would go with the DC hypot.
>>
>> My guess would be (2x120+1000)*2^0.5
>>
>> Make sense?
>
>I believe military aircraft use 440 Hz to reduce the weight of magnetic
>components.
>What is the impact of a short to ground?
>
>I'm not familiar with the term "wild power". Googling didn't help.
is determined by the RPM of the engines so it varies. The voltage is
controlled.
https://i.stack.imgur.com/Hs0LM.png
The ACW bus refers to 'AC Wild'. In the Bombardier Dash 8 it's called
"Variable Freqency AC".
In order to get 28VDC or 400Hz AC conversion can be used, but the ACW
bus can can be used for large loads that are not so fussy such as
de-icing, hydraulic pumps etc.
Unfortunately I don't know the answer to the OP's question. A quick
Google finds that Boeing has called out Hipot testing for DC9 heaters
in SR09340158, so it's not unheard of.
--sp
--
Best regards,
Spehro Pefhany
bruce2...@gmail.com
Apr 28, 2017, 10:14:04 AM4/28/17
to
On 2017-04-27 10:03, Yzordderrex wrote:
> I am interested to know if there is a specification for dielectric
> withstand test for aircraft.
Regarding dielectric, I always wondered why headphones included a few strands of nickel with all those strands of copper. (Maybe just as messenger wire or something)
> withstand test for aircraft.
Neon John
Apr 28, 2017, 11:52:07 AM4/28/17
to
On Fri, 28 Apr 2017 08:00:15 -0400, Spehro Pefhany
<spef...@interlogDOTyou.knowwhat> wrote:
>There are alternators ("AC Generators") on the motors. The frequency
>is determined by the RPM of the engines so it varies. The voltage is
>controlled.
>
>https://i.stack.imgur.com/Hs0LM.png
>
>The ACW bus refers to 'AC Wild'. In the Bombardier Dash 8 it's called
>"Variable Freqency AC".
I'm not an aviation guy but I do know that on larger planes, there is
<spef...@interlogDOTyou.knowwhat> wrote:
>There are alternators ("AC Generators") on the motors. The frequency
>is determined by the RPM of the engines so it varies. The voltage is
>controlled.
>
>https://i.stack.imgur.com/Hs0LM.png
>
>The ACW bus refers to 'AC Wild'. In the Bombardier Dash 8 it's called
>"Variable Freqency AC".
a device that I think is called a constant speed drive that sits
between the engine and generator that drives the generator at a
constant speed.
John
John DeArmond
http://www.neon-john.com
http://www.tnduction.com
Tellico Plains, Occupied TN
See website for email address
rickman
Apr 28, 2017, 12:49:56 PM4/28/17
to
On 4/28/2017 6:39 AM, Clive Arthur wrote:
> On 27/04/2017 18:19, rickman wrote:
>> On 4/27/2017 1:03 PM, Yzordderrex wrote:
>>> I am interested to know if there is a specification for dielectric
>>> withstand test for aircraft. I can't find anything concrete in
>>> DO-160. I know of Mil-std-202, and expect I can apply it to civilian
>>> aircraft.
>>>
>>> I have a client that insists he does not have to hipot and I
>>> disagree. My gut tells me that any gear that is isolated from ground
>>> should be tested in some manner. I think good engineering practice
>>> would dictate a test.
>>>
>>> The unit runs off of 120vac wild power. That is I think 360Hz -
>>> 800Hz. Don't quote me but on that but it is close. We have caps to
>>> ground so would go with the DC hypot.
>>>
>>> My guess would be (2x120+1000)*2^0.5
>>>
>>> Make sense?
>>
>> I believe military aircraft use 440 Hz to reduce the weight of magnetic
>> components.
>
> It's actually 400Hz in aircraft, the significance of 440Hz is that it's
> a standard for A above middle C.
Lol. Thanks
> On 27/04/2017 18:19, rickman wrote:
>> On 4/27/2017 1:03 PM, Yzordderrex wrote:
>>> I am interested to know if there is a specification for dielectric
>>> withstand test for aircraft. I can't find anything concrete in
>>> DO-160. I know of Mil-std-202, and expect I can apply it to civilian
>>> aircraft.
>>>
>>> I have a client that insists he does not have to hipot and I
>>> disagree. My gut tells me that any gear that is isolated from ground
>>> should be tested in some manner. I think good engineering practice
>>> would dictate a test.
>>>
>>> The unit runs off of 120vac wild power. That is I think 360Hz -
>>> 800Hz. Don't quote me but on that but it is close. We have caps to
>>> ground so would go with the DC hypot.
>>>
>>> My guess would be (2x120+1000)*2^0.5
>>>
>>> Make sense?
>>
>> I believe military aircraft use 440 Hz to reduce the weight of magnetic
>> components.
>
> It's actually 400Hz in aircraft, the significance of 440Hz is that it's
> a standard for A above middle C.
--
Rick C
Lasse Langwadt Christensen
Apr 28, 2017, 1:05:32 PM4/28/17
to
Den fredag den 28. april 2017 kl. 12.39.39 UTC+2 skrev Clive Arthur:
> On 27/04/2017 18:19, rickman wrote:
> > On 4/27/2017 1:03 PM, Yzordderrex wrote:
> >> I am interested to know if there is a specification for dielectric
> >> withstand test for aircraft. I can't find anything concrete in
> >> DO-160. I know of Mil-std-202, and expect I can apply it to civilian
> >> aircraft.
> >>
> >> I have a client that insists he does not have to hipot and I
> >> disagree. My gut tells me that any gear that is isolated from ground
> >> should be tested in some manner. I think good engineering practice
> >> would dictate a test.
> >>
> >> The unit runs off of 120vac wild power. That is I think 360Hz -
> >> 800Hz. Don't quote me but on that but it is close. We have caps to
> >> ground so would go with the DC hypot.
> >>
> >> My guess would be (2x120+1000)*2^0.5
> >>
> >> Make sense?
> >
> > I believe military aircraft use 440 Hz to reduce the weight of magnetic
> > components.
>
> It's actually 400Hz in aircraft, the significance of 440Hz is that it's
> a standard for A above middle C.
>
important to keep your airplane in tune ;)
> On 27/04/2017 18:19, rickman wrote:
> > On 4/27/2017 1:03 PM, Yzordderrex wrote:
> >> I am interested to know if there is a specification for dielectric
> >> withstand test for aircraft. I can't find anything concrete in
> >> DO-160. I know of Mil-std-202, and expect I can apply it to civilian
> >> aircraft.
> >>
> >> I have a client that insists he does not have to hipot and I
> >> disagree. My gut tells me that any gear that is isolated from ground
> >> should be tested in some manner. I think good engineering practice
> >> would dictate a test.
> >>
> >> The unit runs off of 120vac wild power. That is I think 360Hz -
> >> 800Hz. Don't quote me but on that but it is close. We have caps to
> >> ground so would go with the DC hypot.
> >>
> >> My guess would be (2x120+1000)*2^0.5
> >>
> >> Make sense?
> >
> > I believe military aircraft use 440 Hz to reduce the weight of magnetic
> > components.
>
> It's actually 400Hz in aircraft, the significance of 440Hz is that it's
> a standard for A above middle C.
>
Joerg
Apr 28, 2017, 1:51:41 PM4/28/17
to
On 2017-04-28 08:51, Neon John wrote:
> On Fri, 28 Apr 2017 08:00:15 -0400, Spehro Pefhany
> <spef...@interlogDOTyou.knowwhat> wrote:
>
>
>> There are alternators ("AC Generators") on the motors. The frequency
>> is determined by the RPM of the engines so it varies. The voltage is
>> controlled.
>>
>> https://i.stack.imgur.com/Hs0LM.png
>>
>> The ACW bus refers to 'AC Wild'. In the Bombardier Dash 8 it's called
>> "Variable Freqency AC".
>
> I'm not an aviation guy but I do know that on larger planes, there is
> a device that I think is called a constant speed drive that sits
> between the engine and generator that drives the generator at a
> constant speed.
>
That was in the days when the pilot donned a thick leather jacket, a
> On Fri, 28 Apr 2017 08:00:15 -0400, Spehro Pefhany
> <spef...@interlogDOTyou.knowwhat> wrote:
>
>
>> There are alternators ("AC Generators") on the motors. The frequency
>> is determined by the RPM of the engines so it varies. The voltage is
>> controlled.
>>
>> https://i.stack.imgur.com/Hs0LM.png
>>
>> The ACW bus refers to 'AC Wild'. In the Bombardier Dash 8 it's called
>> "Variable Freqency AC".
>
> I'm not an aviation guy but I do know that on larger planes, there is
> a device that I think is called a constant speed drive that sits
> between the engine and generator that drives the generator at a
> constant speed.
>
leather cap and goggles :-)
Just kiddding, CSDs are still found on jetliners that are in service but
really modern ones use electronics to do the frequency conversion. Less
weight, less moving parts, more reliable (if designed correctly).
dalai lamah
Apr 28, 2017, 3:12:40 PM4/28/17
to
Un bel giorno Tim Wescott digitò:
>> In many cases aircraft power systems run the return or what would be
>> called neutral in house wiring via the fuselage. That has always scared
>> me but it's often the way it is. Not in very large passenger aircraft
>> though with three-phase APUs and stuff.
>>
>> If it is ground return via fuselage in your case there most likely will
>> only be the usual DO-160 surge and undervoltage requirements, frequency
>> range, EMC, et cetera.
>
> How does that work on fiberglass aircraft?
Usually (but not always) they add metallic meshes among the composite
layers. Especially for lightning protection.
>> In many cases aircraft power systems run the return or what would be
>> called neutral in house wiring via the fuselage. That has always scared
>> me but it's often the way it is. Not in very large passenger aircraft
>> though with three-phase APUs and stuff.
>>
>> If it is ground return via fuselage in your case there most likely will
>> only be the usual DO-160 surge and undervoltage requirements, frequency
>> range, EMC, et cetera.
>
> How does that work on fiberglass aircraft?
layers. Especially for lightning protection.
dalai lamah
Apr 28, 2017, 3:13:54 PM4/28/17
to
Un bel giorno rickman digitò:
In the aerospace sector, it does! :-)
Of course, if you are developing on your own a "catalog" product (to be
sold to anyone who wants to buy it), it's up to you to decide which
standards to comply. But if you are answering to a specific RFI/RFQ or in
general you have to develop a product based on a requirement, it is
uncommon to add further requirements. If in the develompent stage you
discover a serious hazard, usually you first discuss it with your customer.
If the customer hasn't specified a safety requirement, in most cases it is
because he expects that the product will never be in the conditions to
require it. For example, hipot testing is very common for user-operated
equipments, where there is a electric shock hazard for the operator. If you
are developing an equipment that will be installed behind a panel or inside
a closed compartment and will never be touched by anyone (when powered),
hipot testing may be useless.
Of course, if you are developing on your own a "catalog" product (to be
sold to anyone who wants to buy it), it's up to you to decide which
standards to comply. But if you are answering to a specific RFI/RFQ or in
general you have to develop a product based on a requirement, it is
uncommon to add further requirements. If in the develompent stage you
discover a serious hazard, usually you first discuss it with your customer.
If the customer hasn't specified a safety requirement, in most cases it is
because he expects that the product will never be in the conditions to
require it. For example, hipot testing is very common for user-operated
equipments, where there is a electric shock hazard for the operator. If you
are developing an equipment that will be installed behind a panel or inside
a closed compartment and will never be touched by anyone (when powered),
hipot testing may be useless.
rickman
Apr 28, 2017, 3:30:35 PM4/28/17
to
On 4/28/2017 3:13 PM, dalai lamah wrote:
> Un bel giorno rickman digitò:
>
>>>> I am interested to know if there is a specification for dielectric
>>>> withstand test for aircraft. I can't find anything concrete in DO-160.
>>>> I know of Mil-std-202, and expect I can apply it to civilian aircraft.
>>>
>>> Yes, it is quite common to use the MIL-STD-202 method 301 and especially
>>> method 302 (insulation resistance) also for civil aircrafts.
>>>
>>>> I have a client that insists he does not have to hipot and I disagree.
>>>> My gut tells me that any gear that is isolated from ground should be
>>>> tested in some manner. I think good engineering practice would dictate a
>>>> test.
>>>
>>> It may be a good idea to make some measurements during the engineering
>>> tests (just to spot design flaws), but if you don't have a customer
>>> requirement that dictates it, I would avoid to mention it in your
>>> specification. Each additional test requires additional time and money
>>> during the qualification phase.
>>
>> I believe his question is about the general safety requirement implying
>> a hipot test. Not everything about a design has to be explicitly stated
>> as a requirement.
>
> In the aerospace sector, it does! :-)
You misunderstand. When engineers are given requirements for a project,
> Un bel giorno rickman digitò:
>
>>>> I am interested to know if there is a specification for dielectric
>>>> withstand test for aircraft. I can't find anything concrete in DO-160.
>>>> I know of Mil-std-202, and expect I can apply it to civilian aircraft.
>>>
>>> Yes, it is quite common to use the MIL-STD-202 method 301 and especially
>>> method 302 (insulation resistance) also for civil aircrafts.
>>>
>>>> I have a client that insists he does not have to hipot and I disagree.
>>>> My gut tells me that any gear that is isolated from ground should be
>>>> tested in some manner. I think good engineering practice would dictate a
>>>> test.
>>>
>>> It may be a good idea to make some measurements during the engineering
>>> tests (just to spot design flaws), but if you don't have a customer
>>> requirement that dictates it, I would avoid to mention it in your
>>> specification. Each additional test requires additional time and money
>>> during the qualification phase.
>>
>> I believe his question is about the general safety requirement implying
>> a hipot test. Not everything about a design has to be explicitly stated
>> as a requirement.
>
> In the aerospace sector, it does! :-)
or are asked to develop requirements, they start with the requirements
derived from user "wants". These are top level requirements which are
further refined. Many requirements are derived from the general
requirement for the craft to be safe.
> Of course, if you are developing on your own a "catalog" product (to be
> sold to anyone who wants to buy it), it's up to you to decide which
> standards to comply. But if you are answering to a specific RFI/RFQ or in
> general you have to develop a product based on a requirement, it is
> uncommon to add further requirements.
that the unit not catch fire when plugged into 220 volts even though it
is designed only for 120 volt, this will generate requirements on
specific parts of the design for specific ways of meeting the higher
level requirement.
> If in the develompent stage you
> discover a serious hazard, usually you first discuss it with your customer.
> If the customer hasn't specified a safety requirement, in most cases it is
> because he expects that the product will never be in the conditions to
> require it. For example, hipot testing is very common for user-operated
> equipments, where there is a electric shock hazard for the operator. If you
> are developing an equipment that will be installed behind a panel or inside
> a closed compartment and will never be touched by anyone (when powered),
> hipot testing may be useless.
>
--
Clive Arthur
Apr 28, 2017, 3:52:38 PM4/28/17
to
must stand for 'aircraft', so you'd want to keep it above.
Cheers
--
Clive
dalai lamah
Apr 28, 2017, 4:34:40 PM4/28/17
to
Un bel giorno rickman digitò:
>>> I believe his question is about the general safety requirement implying
>>> a hipot test. Not everything about a design has to be explicitly stated
>>> as a requirement.
>>
>> In the aerospace sector, it does! :-)
>
> You misunderstand. When engineers are given requirements for a project,
> or are asked to develop requirements, they start with the requirements
> derived from user "wants". These are top level requirements which are
> further refined. Many requirements are derived from the general
> requirement for the craft to be safe.
>
>> Of course, if you are developing on your own a "catalog" product (to be
>> sold to anyone who wants to buy it), it's up to you to decide which
>> standards to comply. But if you are answering to a specific RFI/RFQ or in
>> general you have to develop a product based on a requirement, it is
>> uncommon to add further requirements.
>
> That is *exactly* the situation I am describing. If a requirement is
> that the unit not catch fire when plugged into 220 volts even though it
> is designed only for 120 volt, this will generate requirements on
> specific parts of the design for specific ways of meeting the higher
> level requirement.
Well, of course. By following this reasoning, each engineering choice (like
>>> a hipot test. Not everything about a design has to be explicitly stated
>>> as a requirement.
>>
>> In the aerospace sector, it does! :-)
>
> You misunderstand. When engineers are given requirements for a project,
> or are asked to develop requirements, they start with the requirements
> derived from user "wants". These are top level requirements which are
> further refined. Many requirements are derived from the general
> requirement for the craft to be safe.
>
>> Of course, if you are developing on your own a "catalog" product (to be
>> sold to anyone who wants to buy it), it's up to you to decide which
>> standards to comply. But if you are answering to a specific RFI/RFQ or in
>> general you have to develop a product based on a requirement, it is
>> uncommon to add further requirements.
>
> That is *exactly* the situation I am describing. If a requirement is
> that the unit not catch fire when plugged into 220 volts even though it
> is designed only for 120 volt, this will generate requirements on
> specific parts of the design for specific ways of meeting the higher
> level requirement.
selecting a capacitor with a specific voltage instead of another) may be
considered a requirement derived from another requirement and so on. I was
just referring to top-level requirements, which in the aerospace sector
have two very distinct characteristics:
(1) The customer gives you *all* the top-level requirements (functional,
environmental, EMC, electrical, mechanical etc etc, usually some hundreds
page of documents). Along with them, usually the customer gives you also
the general requirements for the equipments that have to be installed on
that specific aircraft(s). Usually some other thousand pages of documents.
You have plenty of informations and don't have to assume or add anything.
(2) You have to demonstrate the compliance only for the top-level
requirements, and report the verification method on the compliance matrix
(analysis, test, similarity etc). How you do achieve this compliance, is up
to you.
Hipot testing is by all means a top-level requirement. Like I said, it's
the manufacturer that decides whether it is required or not, based on the
equipment position on the aircraft, on the others equipments connected to
it, and so on. You usually don't have this kind of informations, and
therefore it's not up to you to decide.
Joerg
May 1, 2017, 1:23:09 PM5/1/17
to
you have to develop to a standard, just like you have to in med tech.
BTDT, for more than three decades now. If a design doesn't pass that
agency test it is not a useful design.
>
>> Of course, if you are developing on your own a "catalog" product (to be
>> sold to anyone who wants to buy it), it's up to you to decide which
>> standards to comply. But if you are answering to a specific RFI/RFQ or in
>> general you have to develop a product based on a requirement, it is
>> uncommon to add further requirements.
>
> That is *exactly* the situation I am describing. If a requirement is
> that the unit not catch fire when plugged into 220 volts even though it
> is designed only for 120 volt, this will generate requirements on
> specific parts of the design for specific ways of meeting the higher
> level requirement.
>
designers of aircraft electronics must follow.
[...]
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