X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Sender: To: lml@lancaironline.net Date: Thu, 28 Mar 2013 13:58:40 -0400 Message-ID: X-Original-Return-Path: Received: from cdptpa-omtalb.mail.rr.com ([75.180.132.120] verified) by logan.com (CommuniGate Pro SMTP 6.0.3) with ESMTP id 6162918 for lml@lancaironline.net; Thu, 28 Mar 2013 12:36:44 -0400 Received-SPF: pass receiver=logan.com; client-ip=75.180.132.120; envelope-from=super_chipmunk@roadrunner.com X-Original-Return-Path: X-Authority-Analysis: v=2.0 cv=XNeyuHdE c=1 sm=0 a=+kuJ7Sa7hUpxs7xJxzDFzQ==:17 a=AeF9CLZUGkAA:10 a=FVgTifo7gLcA:10 a=zTVDa7HKqxcA:10 a=doupyKFmAAAA:8 a=YgXmjUs_AvgA:10 a=Ia-xEzejAAAA:8 a=NwjmyzuvzmdRmm1UgVIA:9 a=QEXdDO2ut3YA:10 a=EzXvWhQp4_cA:10 a=6vbH-79yvWTUB3pi:21 a=CBw-88o5CTTLSLcm:21 a=CjxXgO3LAAAA:8 a=lU1WgpgTHyhdMo1ujAEA:9 a=_W_S_7VecoQA:10 a=rC2wZJ5BpNYA:10 a=KVomB8rjeGMiu__H:21 a=+kuJ7Sa7hUpxs7xJxzDFzQ==:117 X-Cloudmark-Score: 0 X-Authenticated-User: X-Originating-IP: 76.179.81.18 Received: from [76.179.81.18] ([76.179.81.18:57456] helo=WilliamHP) by cdptpa-oedge02.mail.rr.com (envelope-from ) (ecelerity 2.2.3.46 r()) with ESMTP id 9A/FD-04559-87174515; Thu, 28 Mar 2013 16:36:08 +0000 X-Original-Message-ID: <8D78B88FFFD84C86AB8E10E46D34C135@WilliamHP> From: "Bill Wade" X-Original-To: "Lancair Mailing List" References: In-Reply-To: Subject: Re: [Norton AntiSpam][LML] Re: Hydraulic gear pump failure - Relays X-Original-Date: Thu, 28 Mar 2013 12:36:04 -0400 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_00BB_01CE2BB0.D0012EE0" X-Priority: 3 X-MSMail-Priority: Normal Importance: Normal X-Mailer: Microsoft Windows Live Mail 15.4.3555.308 X-MimeOLE: Produced By Microsoft MimeOLE V15.4.3555.308 This is a multi-part message in MIME format. ------=_NextPart_000_00BB_01CE2BB0.D0012EE0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable Would there be any drawback to using a higher- rated contactor? I = found the Lancair part to be a P.O.S.- it was marked continuous duty but = when put on a power supply it rapidly overheated and shorted to the = case. Instead I=E2=80=99m using an antique 50A Leach B-5B aircraft style that = easily operated for hours. The pump supplied with my IV-P draws a = maximum of 50A, so the Leach might be marginal but I think I=E2=80=99ll = try it initially. On Colin=E2=80=99s recommendation I also purchased a TYCO LEV100A5ANH , = rated 100A that I could use instead, or elsewhere. The Leach draws = 0.16A, the TYCO draws 0.25A at 28V. The Lancair- supplied Suco pressure = switch is rated for 4A as best I can determine so either unit should be = compatible. I don=E2=80=99t know what other models might use but consider the = contacts inside the pressure switches. If they should get overloaded and = weld closed the effect would be the same as welding the relay points. = -Bill Wade From: Gary Casey=20 Sent: Thursday, March 28, 2013 9:36 AM To: lml@lancaironline.net=20 Subject: [Norton AntiSpam][LML] Re: Hydraulic gear pump failure - Relays Pardon me if I'm jumping into a discussion a little late (and a dollar = short), but there might be some confusion on how and why relays are = designed for intermittent duty. As an example, take a standard master = relay. It is rated for continuous duty and something like 80 amps. = That means the coil won't overheat if left on forever and that the = contacts also won't overheat when passing 80 amps and that the contacts = won't weld when interrupting 80 amps. It is often the limitations when = opening the circuit that determines the rating. Current will try to = keep flowing and if the contacts don't separate rapidly and with enough = force the inevitable arc could create enough heat to weld the contacts = and prevent opening. If it is desired to design a relay in the same = package (for cost, size and weight reasons) that can be used = intermittently to pass a much higher current the design parameters are = different. More force is required to increase the rate at which the = contacts are opened so a higher force spring is installed. Then more = force is required to close the contacts, so fewer turns of heavier wire = are used in the coil (that's right, FEWER turns, but that's another = discussion). The result is that the relay can now successfully switch = maybe 300 amps, but the coil will overheat after a few minutes of = operation. That's the difference between a master and a starter relay. = And I have never, ever heard of using a relay as the "weak link" in the = system. Gary ps: My Lancair list emails now come all messed up (see below). Why is = that? Am I doing something wrong? The only caveat with that fix, Fred, is that intermittent relays are = ther=3D e for a purpose. They are supposed to be the weak link in a circuit where = =3D a continuous stuck relay could result in greater problems than a = failure.=3D20 Does that protective function matter in this circuit?=3D0D Should be considered.=3D0D John=3D0D ------=_NextPart_000_00BB_01CE2BB0.D0012EE0 Content-Type: text/html; charset="utf-8" Content-Transfer-Encoding: quoted-printable
  Would there be any drawback to using a higher- rated = contactor? I=20 found the Lancair part to be a P.O.S.- it was marked continuous duty but = when=20 put on a power supply it rapidly overheated and shorted to the = case.
 
Instead I=E2=80=99m using an antique 50A Leach B-5B aircraft style = that easily=20 operated for hours. The pump supplied with my IV-P draws a maximum of = 50A, so=20 the Leach might be marginal but I think I=E2=80=99ll try it = initially.
 
On Colin=E2=80=99s recommendation I also purchased a TYCO = LEV100A5ANH , rated 100A=20 that I could use instead, or elsewhere. The Leach draws 0.16A, the TYCO = draws=20 0.25A at 28V. The Lancair- supplied Suco pressure switch is rated for 4A = as best=20 I can determine so either unit should be compatible.
 
  I don=E2=80=99t know what other models might use but = consider the contacts=20 inside the pressure switches. If they should get overloaded and weld = closed the=20 effect would be the same as welding the relay points.  -Bill = Wade
 
From: Gary Casey
Sent: Thursday, March 28, 2013 9:36 AM
Subject: [Norton AntiSpam][LML] Re: Hydraulic gear pump = failure -=20 Relays
 
Pardon me if I'm jumping into a discussion a little late (and a = dollar=20 short), but there might be some confusion on how and why relays are = designed for=20 intermittent duty.  As an example, take a standard master = relay.  It=20 is rated for continuous duty and something like 80 amps.  That = means the=20 coil won't overheat if left on forever and that the contacts also won't = overheat=20 when passing 80 amps and that the contacts won't weld when interrupting = 80=20 amps.  It is often the limitations when opening the circuit that = determines=20 the rating.  Current will try to keep flowing and if the contacts = don't=20 separate rapidly and with enough force the inevitable arc could create = enough=20 heat to weld the contacts and prevent opening.  If it is desired to = design=20 a relay in the same package (for cost, size and weight reasons) that can = be used=20 intermittently to pass a much higher current the design parameters are=20 different.  More force is required to increase the rate at which = the=20 contacts are opened so a higher force spring is installed.  Then = more force=20 is required to close the contacts, so fewer turns of heavier wire are = used in=20 the coil (that's right, FEWER turns, but that's another = discussion).  The=20 result is that the relay can now successfully switch maybe 300 amps, but = the=20 coil will overheat after a few minutes of operation.  That's the = difference=20 between a master and a starter relay.  And I have never, ever heard = of=20 using a relay as the "weak link" in the system.
Gary
ps:  My Lancair list emails now come all messed up (see = below). =20 Why is that?  Am I doing something wrong?
 
The=20 only caveat with that fix, Fred, is that intermittent relays are = ther=3Defor=20 a purpose.  They are supposed to be the weak link in a circuit = where=20 =3Dacontinuous=20 stuck relay could result in greater problems than a = failure.=3D20Does=20 that protective function matter in this circuit?=3D0DShould=20 be  considered.=3D0DJohn=3D0D
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