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| Author |
Message |
TSL
electronics forum beginner
Joined: 18 Jul 2006
Posts: 7
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 Posted: Tue Jul 18, 2006 11:42 pm Post subject:
Circuit design for 10.5 amp 230V 2HP motor @ 3450rpm
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Final stage of rebuilding 1940's 10" Craftsman table saw (think
tank/bulletproof) with belt drive. Been doing some electrical research
while setting up my woodshop. Using Allen Bradley switches with
key-lock on/off and 2 e-stop buttons for each of the larger power items
(one at the switch panel and one on or directly next to the repsective
machine), along with swap out of all larger 120V tools to special plugs
so switch panel can't be endrun. Have 13yo son and don't want
curiosity getting the better of him and his friends in my absence.
Questions:
1) can and should an AC motor starter be used on my 10.5 amp 230V 2hp
3450rpm drive motor to give the motor longer life - and if so should an
electric brake be installed also? What are the theories and pros/cons?
2) what is the difference in design between a transformer rated switch
@ 120V 50/60htz versus a "full voltage" switch with identical rating -
are the contacts supposed to be different? I ask because I noticed in
my quest for the AB switches (bought used to save money) the contact
blocks for the switches appear identical in both design and model #
regardless if they are rated/listed for transformer power versus full
voltage (which I'm assuming is raw power from my house).
3) what in blazes does the "L1, L2, L3, etc" and "T1, T2' T3, etc" tags
mean in motor circuit and wiring diagrams? I'm assuming that "common"
is the nuetral. And when the nuetral and ground from my box (WA state)
are joined, how, if at all, are they to be distinguished at the motor?
Nuff for now. TYIA!
TSL |
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Another Wally
electronics forum beginner
Joined: 11 Jul 2006
Posts: 3
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| Posted: Wed Jul 19, 2006 12:55 am Post subject:
Re: Circuit design for 10.5 amp 230V 2HP motor @ 3450rpm
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"TSL" <WestCoastJagLTD@msn.com> wrote in message
news:1153266170.559382.72050@b28g2000cwb.googlegroups.com...
| Quote: | Final stage of rebuilding 1940's 10" Craftsman table saw (think
tank/bulletproof) with belt drive. Been doing some electrical research
while setting up my woodshop. Using Allen Bradley switches with
key-lock on/off and 2 e-stop buttons for each of the larger power items
(one at the switch panel and one on or directly next to the repsective
machine), along with swap out of all larger 120V tools to special plugs
so switch panel can't be endrun. Have 13yo son and don't want
curiosity getting the better of him and his friends in my absence.
Questions:
1) can and should an AC motor starter be used on my 10.5 amp 230V 2hp
3450rpm drive motor to give the motor longer life - and if so should an
electric brake be installed also? What are the theories and pros/cons?
2) what is the difference in design between a transformer rated switch
@ 120V 50/60htz versus a "full voltage" switch with identical rating -
are the contacts supposed to be different? I ask because I noticed in
my quest for the AB switches (bought used to save money) the contact
blocks for the switches appear identical in both design and model #
regardless if they are rated/listed for transformer power versus full
voltage (which I'm assuming is raw power from my house).
3) what in blazes does the "L1, L2, L3, etc" and "T1, T2' T3, etc" tags
mean in motor circuit and wiring diagrams? I'm assuming that "common"
is the nuetral. And when the nuetral and ground from my box (WA state)
are joined, how, if at all, are they to be distinguished at the motor?
Nuff for now. TYIA!
TSL
I would suggest you get a qualified electrician in to wire up these items, |
it is evident you don't have a clue. |
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John Perry
electronics forum addict
Joined: 07 May 2005
Posts: 83
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| Posted: Wed Jul 19, 2006 3:10 am Post subject:
Re: Circuit design for 10.5 amp 230V 2HP motor @ 3450rpm
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Another Wally wrote:
| Quote: | "TSL" <WestCoastJagLTD@msn.com> wrote in message
.... |
| Quote: |
3) what in blazes does the "L1, L2, L3, etc" and "T1, T2' T3, etc" tags
mean in motor circuit and wiring diagrams? I'm assuming that "common"
is the nuetral. And when the nuetral and ground from my box (WA state)
are joined, how, if at all, are they to be distinguished at the motor?
Nuff for now. TYIA!
TSL
I would suggest you get a qualified electrician in to wire up these items,
it is evident you don't have a clue.
|
Heck, just tell him straight out that he can't use that motor. It's
unlikely in the extreme that his home provides the 3-phase power he
needs to drive that motor. That's what his electrician is going to tell
him.
John Perry |
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Robert Latest
electronics forum Guru
Joined: 09 May 2005
Posts: 304
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| Posted: Wed Jul 19, 2006 9:31 am Post subject:
Re: Circuit design for 10.5 amp 230V 2HP motor @ 3450rpm
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On Tue, 18 Jul 2006 23:10:47 -0400,
John Perry <jp@no.spam> wrote
in Msg. <Eohvg.333056$5Z.146291@dukeread02>
| Quote: | Heck, just tell him straight out that he can't use that motor. It's
unlikely in the extreme that his home provides the 3-phase power he
needs to drive that motor. That's what his electrician is going to tell
him.
|
Depends on where he lives. In Europe, 3-phase 400V lines go into every
home.
robert |
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Roger Hamlett
electronics forum Guru
Joined: 28 Apr 2005
Posts: 302
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| Posted: Wed Jul 19, 2006 10:12 am Post subject:
Re: Circuit design for 10.5 amp 230V 2HP motor @ 3450rpm
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"TSL" <WestCoastJagLTD@msn.com> wrote in message
news:1153266170.559382.72050@b28g2000cwb.googlegroups.com...
| Quote: | Final stage of rebuilding 1940's 10" Craftsman table saw (think
tank/bulletproof) with belt drive. Been doing some electrical research
while setting up my woodshop. Using Allen Bradley switches with
key-lock on/off and 2 e-stop buttons for each of the larger power items
(one at the switch panel and one on or directly next to the repsective
machine), along with swap out of all larger 120V tools to special plugs
so switch panel can't be endrun. Have 13yo son and don't want
curiosity getting the better of him and his friends in my absence.
Questions:
1) can and should an AC motor starter be used on my 10.5 amp 230V 2hp
3450rpm drive motor to give the motor longer life - and if so should an
electric brake be installed also? What are the theories and pros/cons?
2) what is the difference in design between a transformer rated switch
@ 120V 50/60htz versus a "full voltage" switch with identical rating -
are the contacts supposed to be different? I ask because I noticed in
my quest for the AB switches (bought used to save money) the contact
blocks for the switches appear identical in both design and model #
regardless if they are rated/listed for transformer power versus full
voltage (which I'm assuming is raw power from my house).
3) what in blazes does the "L1, L2, L3, etc" and "T1, T2' T3, etc" tags
mean in motor circuit and wiring diagrams? I'm assuming that "common"
is the nuetral. And when the nuetral and ground from my box (WA state)
are joined, how, if at all, are they to be distinguished at the motor?
Nuff for now. TYIA!
TSL
The only possibility for you, will be a 3 phase inverter unit. The motor |
you have, is industrial, and built to run on 3 phase. it sounds as if it
can be wired for either star, or delta configurations (hence both ends of
each winding are available). A normal house supply, will only be single
phase, so three choices exist. First to pay to have 3phase electricity
supplied to your house (expensive), or buy an inverter unit, which
generates a 'synthetic' 3phase from your single phase supply. The latter
in general, is significantly cheaper than getting 3phase power, and has
the added advantage that most units will include options for soft start,
and variable speed. The third option is to substitute a single phase
motor.
Look at:
http://www.inverter.co.uk/electricmotorcontrols/inverters/lg/ic5.htm
The SV022iC5-1F, would probably be the unit for your motor.
However _seriously_, if you have to ask the question, you do not have the
experience, to wire such a unit safely, and if you value your own, and
your families lives, you should consider getting a professional to set
this up for you.
Best Wishes |
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Glen Walpert
electronics forum Guru Wannabe
Joined: 04 May 2005
Posts: 134
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| Posted: Wed Jul 19, 2006 1:17 pm Post subject:
Re: Circuit design for 10.5 amp 230V 2HP motor @ 3450rpm
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On 18 Jul 2006 16:42:50 -0700, "TSL" <WestCoastJagLTD@msn.com> wrote:
| Quote: | Final stage of rebuilding 1940's 10" Craftsman table saw (think
tank/bulletproof) with belt drive. Been doing some electrical research
while setting up my woodshop. Using Allen Bradley switches with
key-lock on/off and 2 e-stop buttons for each of the larger power items
(one at the switch panel and one on or directly next to the repsective
machine), along with swap out of all larger 120V tools to special plugs
so switch panel can't be endrun. Have 13yo son and don't want
curiosity getting the better of him and his friends in my absence.
Questions:
1) can and should an AC motor starter be used on my 10.5 amp 230V 2hp
3450rpm drive motor to give the motor longer life - and if so should an
electric brake be installed also? What are the theories and pros/cons?
|
A motor starter (controller) should be used with any motor you want to
protect from overload, and the overload trip elements in it must be
sized to the protected motor. Look for a table of trip element number
vs full load amps (FLA) and buy the right trip elements new.
| Quote: | 2) what is the difference in design between a transformer rated switch
@ 120V 50/60htz versus a "full voltage" switch with identical rating -
are the contacts supposed to be different? I ask because I noticed in
my quest for the AB switches (bought used to save money) the contact
blocks for the switches appear identical in both design and model #
regardless if they are rated/listed for transformer power versus full
voltage (which I'm assuming is raw power from my house).
|
Perhaps different voltage rating between coil and contacts? Try the
mfgr's web site?
| Quote: | 3) what in blazes does the "L1, L2, L3, etc" and "T1, T2' T3, etc" tags
mean in motor circuit and wiring diagrams? I'm assuming that "common"
is the nuetral. And when the nuetral and ground from my box (WA state)
are joined, how, if at all, are they to be distinguished at the motor?
|
L1, L2 and L3 refer to line in of three phase power, T1 etc are the
motor terminal connections for a 3 phase motor. If these are on the
wiring diagram for your controller and you have a single phase motor,
no problem, run your two hots in L1 and L3 and out T1 and T3, after
verifying that L1 - T1 and L3 - T3 are the circuits which contain the
overload elements. If these designations are on your motor then it is
a three phase motor and you need a phase converter. There is a good
rotary phase converter design posted to the rec.crafts.metalworking
newsgroup "dropbox", someone on that NG could tell you where it is.
The difference between neutral and ground, which are joined only in
your panel, is that the neutral normally carries load current and the
ground *only* carries fault current in the event of a short circuit to
ground. Unless you need 120 V for the controller coil you should not
even need to run a neutral to a 240 V motor circuit, but the ground
(AKA safety ground) is always mandatory and must be connected solidly
to all metal enclosures of energised equipment.
While I have no problem with DIY electrical work, I very strongly
recommend you have your work inspected by a licensed electrical
underwriter (inspector), and that you line up the inspector and
discuss the job with him before you start. |
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Michael A. Terrell
electronics forum Guru
Joined: 24 Mar 2005
Posts: 2291
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| Posted: Wed Jul 19, 2006 2:50 pm Post subject:
Re: Circuit design for 10.5 amp 230V 2HP motor @ 3450rpm
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Robert Latest wrote:
| Quote: |
On Tue, 18 Jul 2006 23:10:47 -0400,
John Perry <jp@no.spam> wrote
in Msg. <Eohvg.333056$5Z.146291@dukeread02
Heck, just tell him straight out that he can't use that motor. It's
unlikely in the extreme that his home provides the 3-phase power he
needs to drive that motor. That's what his electrician is going to tell
him.
Depends on where he lives. In Europe, 3-phase 400V lines go into every
home.
robert
|
The motor data indicates that it was made for the US market, and he
is posting from a US based ISP.
--
Service to my country? Been there, Done that, and I've got my DD214 to
prove it.
Member of DAV #85.
Michael A. Terrell
Central Florida |
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TSL
electronics forum beginner
Joined: 18 Jul 2006
Posts: 7
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| Posted: Wed Jul 19, 2006 4:08 pm Post subject:
Re: Circuit design for 10.5 amp 230V 2HP motor @ 3450rpm
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OK Gentlemen, first it would appear that this request for assitance is
misplaced in this advanced a forum. Second, it IS NOT a 3 phase motor.
It is a 1 phase motor - and I am very clear about the difference. I
asked about the L3 as an abstract type question not specifically tied
to my situation.
And at the risk of displaying obvious umbrage at some of the remarks, I
most definitely do have a clue about AC - at least the 120/240V variety
common to my home. I simply need some additional information to fill
out the gaps.
Should it help establish my level of understanding, I have completely
rewired and redesigned the circuits in my 3 bay garage to make sense
for the machines and power needs I employ, including a 'pony box" with
a 60 amp 240V draw off the main box so I don't have to run wire so far.
I've also succesfully installed a ten circuit gas generator interface
for when the power goes out (which happens 4 to 5 times a year from
nasty windstorms).
I won't pretend I completely understand 3 phase - but I can tell you
that I don't have it in my home and I am not interested in using a 3
phase motor, dirt cheap though they may be, as I have a perfectly good
2HP motor.
So perhaps we could start over.
Thanx.
TSL
Another Wally wrote:
| Quote: | "TSL" <WestCoastJagLTD@msn.com> wrote in message
news:1153266170.559382.72050@b28g2000cwb.googlegroups.com...
Final stage of rebuilding 1940's 10" Craftsman table saw (think
tank/bulletproof) with belt drive. Been doing some electrical research
while setting up my woodshop. Using Allen Bradley switches with
key-lock on/off and 2 e-stop buttons for each of the larger power items
(one at the switch panel and one on or directly next to the repsective
machine), along with swap out of all larger 120V tools to special plugs
so switch panel can't be endrun. Have 13yo son and don't want
curiosity getting the better of him and his friends in my absence.
Questions:
1) can and should an AC motor starter be used on my 10.5 amp 230V 2hp
3450rpm drive motor to give the motor longer life - and if so should an
electric brake be installed also? What are the theories and pros/cons?
2) what is the difference in design between a transformer rated switch
@ 120V 50/60htz versus a "full voltage" switch with identical rating -
are the contacts supposed to be different? I ask because I noticed in
my quest for the AB switches (bought used to save money) the contact
blocks for the switches appear identical in both design and model #
regardless if they are rated/listed for transformer power versus full
voltage (which I'm assuming is raw power from my house).
3) what in blazes does the "L1, L2, L3, etc" and "T1, T2' T3, etc" tags
mean in motor circuit and wiring diagrams? I'm assuming that "common"
is the nuetral. And when the nuetral and ground from my box (WA state)
are joined, how, if at all, are they to be distinguished at the motor?
Nuff for now. TYIA!
TSL
I would suggest you get a qualified electrician in to wire up these items,
it is evident you don't have a clue. |
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Tim Wescott
electronics forum Guru
Joined: 04 May 2005
Posts: 707
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| Posted: Wed Jul 19, 2006 4:35 pm Post subject:
Re: Circuit design for 10.5 amp 230V 2HP motor @ 3450rpm
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|
Glen Walpert wrote:
| Quote: | On 18 Jul 2006 16:42:50 -0700, "TSL" <WestCoastJagLTD@msn.com> wrote:
Final stage of rebuilding 1940's 10" Craftsman table saw (think
tank/bulletproof) with belt drive. Been doing some electrical research
while setting up my woodshop. Using Allen Bradley switches with
key-lock on/off and 2 e-stop buttons for each of the larger power items
(one at the switch panel and one on or directly next to the repsective
machine), along with swap out of all larger 120V tools to special plugs
so switch panel can't be endrun. Have 13yo son and don't want
curiosity getting the better of him and his friends in my absence.
Questions:
1) can and should an AC motor starter be used on my 10.5 amp 230V 2hp
3450rpm drive motor to give the motor longer life - and if so should an
electric brake be installed also? What are the theories and pros/cons?
A motor starter (controller) should be used with any motor you want to
protect from overload, and the overload trip elements in it must be
sized to the protected motor. Look for a table of trip element number
vs full load amps (FLA) and buy the right trip elements new.
2) what is the difference in design between a transformer rated switch
@ 120V 50/60htz versus a "full voltage" switch with identical rating -
are the contacts supposed to be different? I ask because I noticed in
my quest for the AB switches (bought used to save money) the contact
blocks for the switches appear identical in both design and model #
regardless if they are rated/listed for transformer power versus full
voltage (which I'm assuming is raw power from my house).
Perhaps different voltage rating between coil and contacts? Try the
mfgr's web site?
3) what in blazes does the "L1, L2, L3, etc" and "T1, T2' T3, etc" tags
mean in motor circuit and wiring diagrams? I'm assuming that "common"
is the nuetral. And when the nuetral and ground from my box (WA state)
are joined, how, if at all, are they to be distinguished at the motor?
L1, L2 and L3 refer to line in of three phase power, T1 etc are the
motor terminal connections for a 3 phase motor. If these are on the
wiring diagram for your controller and you have a single phase motor,
no problem, run your two hots in L1 and L3 and out T1 and T3, after
verifying that L1 - T1 and L3 - T3 are the circuits which contain the
overload elements. If these designations are on your motor then it is
a three phase motor and you need a phase converter. There is a good
rotary phase converter design posted to the rec.crafts.metalworking
newsgroup "dropbox", someone on that NG could tell you where it is.
The difference between neutral and ground, which are joined only in
your panel, is that the neutral normally carries load current and the
ground *only* carries fault current in the event of a short circuit to
ground. Unless you need 120 V for the controller coil you should not
even need to run a neutral to a 240 V motor circuit, but the ground
(AKA safety ground) is always mandatory and must be connected solidly
to all metal enclosures of energised equipment.
While I have no problem with DIY electrical work, I very strongly
recommend you have your work inspected by a licensed electrical
underwriter (inspector), and that you line up the inspector and
discuss the job with him before you start.
|
I second that. I'm an electronics engineer with a master's degree, 15
years of experience, 5 years of electrical installation experience
before that, etc., etc. -- and if I did work of that magnitude in my
home I'd happily pay to have a second pair of eyes take a look at it
before I fired it up.
Most insurance companies will deny coverage (or at least try) if
home-done, uninspected electrical work catches fire. Many will try to
deny coverage if an arsonist starts a fire on the outside wall of a
building housing such work. Getting the thing inspected in small potatoes.
--
Tim Wescott
Wescott Design Services
http://www.wescottdesign.com
Posting from Google? See http://cfaj.freeshell.org/google/
"Applied Control Theory for Embedded Systems" came out in April.
See details at http://www.wescottdesign.com/actfes/actfes.html |
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TSL
electronics forum beginner
Joined: 18 Jul 2006
Posts: 7
|
| Posted: Wed Jul 19, 2006 5:04 pm Post subject:
Re: Circuit design for 10.5 amp 230V 2HP motor @ 3450rpm
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|
OK, now were getting somewhere. Thank you Mr Walpert.
I am clear about the difference between the ground and nuetral in
general terms. What I am unclear about is why a 240V motor (which is
also on my compressor) does not need the nuetral? This is one of the
gaps in my understanding. It bugged me when I hooked up my compressor
but i just let it go. With what I am doing now, I'd really like to
understand why 240V seems to change the whole playing field and drops
the nuetral.
My Dayton 1 PHASE 2HP 115/230V, 21amp/11.5amp, 3450rpm motor on a nema
H56 frame is sealed so as to not allow in wood dust and chips and
debris and is specific for my application. I am clear that I have the
option of either wiring it as 115 or 230, but the 10.5 amps running
through 2 hot lines is an easier and smarter move for my situation than
21 amps through one hot wire. I have a 240V dual 15amp breaker in my
pony box that awaits my wiring. I will take power from it down to the
control panel and run it through an AB 2 position maintained key switch
with two contact blocks on it (a 120 line going to each contact block)
and then through a 2 position estop button on the panel, also with two
contact blocks. Then it will run to a stud mouted outlet with a
twist/lock receptical. A ten gauge industrial sheathed cord with the
male plug then runs to another identical estop positioned on the saw
itself, then to a 240V foot switch, and then to the motor. But as I
started getting deeper into the AB world, I bumped into these motor
starters and as far as I can tell, they are used on 1 phase motors in
some instances. As best I can tell, they help the motor ease into full
rpm and give it "cleaner" power and better circuit protection - which
is supposed to increase motor life. Thus my question about using a
motor starter setup between the control panel and the wall outlet. But
it may just be overkill and hubris - I don't know. I need help
understanding the pros/cons.
While I thank you for your concern, I work at an establishment with a
full time maintanence crew; one of which is a certified elctrician. I
am very clear about the code in my area and have followed it to the
letter; including distances from outer stud to romex feed holes, proper
gauge romex and proper amperage outlets etc.. My 3 bay garage is almost
totally bare rafters and studs and thus it is very simple to run romex
along the top of the rafters and staple them in along other existing
wires. In the cases when I dropped a wire to one of the 2 small
finished walls (code mandated with fireproof drywall where garage meets
house) I start conduit in the rafters and route it down onto the
drywall. I am a systems geek by profession and extremely meticulous
about safety in all my endeavors; right down to safety glasses and ear
protection when I just mow the lawn.
As to the transformer versus full voltage, I entertained that the
voltage may be different. But when they attatch an 800T-XA contact
block that will handle up to 600V (though only at 15 amps) and the same
contact blocks are used on both, and the operators themselves show no
design difference whatsoever, I began to wonder whether it was just a
case of categorization to satisfy NEMA or that other standard that
escapes me at the moment. It may only be something employed with the
illuminated switches. But the illumination contact blocks for the 120V
full voltage and transformer voltage appear identical in both style and
design #.
Again, thank you for your time.
TSL
Glen Walpert wrote:
| Quote: | On 18 Jul 2006 16:42:50 -0700, "TSL" <WestCoastJagLTD@msn.com> wrote:
Final stage of rebuilding 1940's 10" Craftsman table saw (think
tank/bulletproof) with belt drive. Been doing some electrical research
while setting up my woodshop. Using Allen Bradley switches with
key-lock on/off and 2 e-stop buttons for each of the larger power items
(one at the switch panel and one on or directly next to the repsective
machine), along with swap out of all larger 120V tools to special plugs
so switch panel can't be endrun. Have 13yo son and don't want
curiosity getting the better of him and his friends in my absence.
Questions:
1) can and should an AC motor starter be used on my 10.5 amp 230V 2hp
3450rpm drive motor to give the motor longer life - and if so should an
electric brake be installed also? What are the theories and pros/cons?
A motor starter (controller) should be used with any motor you want to
protect from overload, and the overload trip elements in it must be
sized to the protected motor. Look for a table of trip element number
vs full load amps (FLA) and buy the right trip elements new.
2) what is the difference in design between a transformer rated switch
@ 120V 50/60htz versus a "full voltage" switch with identical rating -
are the contacts supposed to be different? I ask because I noticed in
my quest for the AB switches (bought used to save money) the contact
blocks for the switches appear identical in both design and model #
regardless if they are rated/listed for transformer power versus full
voltage (which I'm assuming is raw power from my house).
Perhaps different voltage rating between coil and contacts? Try the
mfgr's web site?
3) what in blazes does the "L1, L2, L3, etc" and "T1, T2' T3, etc" tags
mean in motor circuit and wiring diagrams? I'm assuming that "common"
is the nuetral. And when the nuetral and ground from my box (WA state)
are joined, how, if at all, are they to be distinguished at the motor?
L1, L2 and L3 refer to line in of three phase power, T1 etc are the
motor terminal connections for a 3 phase motor. If these are on the
wiring diagram for your controller and you have a single phase motor,
no problem, run your two hots in L1 and L3 and out T1 and T3, after
verifying that L1 - T1 and L3 - T3 are the circuits which contain the
overload elements. If these designations are on your motor then it is
a three phase motor and you need a phase converter. There is a good
rotary phase converter design posted to the rec.crafts.metalworking
newsgroup "dropbox", someone on that NG could tell you where it is.
The difference between neutral and ground, which are joined only in
your panel, is that the neutral normally carries load current and the
ground *only* carries fault current in the event of a short circuit to
ground. Unless you need 120 V for the controller coil you should not
even need to run a neutral to a 240 V motor circuit, but the ground
(AKA safety ground) is always mandatory and must be connected solidly
to all metal enclosures of energised equipment.
While I have no problem with DIY electrical work, I very strongly
recommend you have your work inspected by a licensed electrical
underwriter (inspector), and that you line up the inspector and
discuss the job with him before you start. |
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TSL
electronics forum beginner
Joined: 18 Jul 2006
Posts: 7
|
| Posted: Wed Jul 19, 2006 5:09 pm Post subject:
Re: Circuit design for 10.5 amp 230V 2HP motor @ 3450rpm
|
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|
OK, OK, I get it. I'll have it inspected. You had me @ the insurance
thing . . .
TSL
Tim Wescott wrote:
| Quote: | Glen Walpert wrote:
On 18 Jul 2006 16:42:50 -0700, "TSL" <WestCoastJagLTD@msn.com> wrote:
Final stage of rebuilding 1940's 10" Craftsman table saw (think
tank/bulletproof) with belt drive. Been doing some electrical research
while setting up my woodshop. Using Allen Bradley switches with
key-lock on/off and 2 e-stop buttons for each of the larger power items
(one at the switch panel and one on or directly next to the repsective
machine), along with swap out of all larger 120V tools to special plugs
so switch panel can't be endrun. Have 13yo son and don't want
curiosity getting the better of him and his friends in my absence.
Questions:
1) can and should an AC motor starter be used on my 10.5 amp 230V 2hp
3450rpm drive motor to give the motor longer life - and if so should an
electric brake be installed also? What are the theories and pros/cons?
A motor starter (controller) should be used with any motor you want to
protect from overload, and the overload trip elements in it must be
sized to the protected motor. Look for a table of trip element number
vs full load amps (FLA) and buy the right trip elements new.
2) what is the difference in design between a transformer rated switch
@ 120V 50/60htz versus a "full voltage" switch with identical rating -
are the contacts supposed to be different? I ask because I noticed in
my quest for the AB switches (bought used to save money) the contact
blocks for the switches appear identical in both design and model #
regardless if they are rated/listed for transformer power versus full
voltage (which I'm assuming is raw power from my house).
Perhaps different voltage rating between coil and contacts? Try the
mfgr's web site?
3) what in blazes does the "L1, L2, L3, etc" and "T1, T2' T3, etc" tags
mean in motor circuit and wiring diagrams? I'm assuming that "common"
is the nuetral. And when the nuetral and ground from my box (WA state)
are joined, how, if at all, are they to be distinguished at the motor?
L1, L2 and L3 refer to line in of three phase power, T1 etc are the
motor terminal connections for a 3 phase motor. If these are on the
wiring diagram for your controller and you have a single phase motor,
no problem, run your two hots in L1 and L3 and out T1 and T3, after
verifying that L1 - T1 and L3 - T3 are the circuits which contain the
overload elements. If these designations are on your motor then it is
a three phase motor and you need a phase converter. There is a good
rotary phase converter design posted to the rec.crafts.metalworking
newsgroup "dropbox", someone on that NG could tell you where it is.
The difference between neutral and ground, which are joined only in
your panel, is that the neutral normally carries load current and the
ground *only* carries fault current in the event of a short circuit to
ground. Unless you need 120 V for the controller coil you should not
even need to run a neutral to a 240 V motor circuit, but the ground
(AKA safety ground) is always mandatory and must be connected solidly
to all metal enclosures of energised equipment.
While I have no problem with DIY electrical work, I very strongly
recommend you have your work inspected by a licensed electrical
underwriter (inspector), and that you line up the inspector and
discuss the job with him before you start.
I second that. I'm an electronics engineer with a master's degree, 15
years of experience, 5 years of electrical installation experience
before that, etc., etc. -- and if I did work of that magnitude in my
home I'd happily pay to have a second pair of eyes take a look at it
before I fired it up.
Most insurance companies will deny coverage (or at least try) if
home-done, uninspected electrical work catches fire. Many will try to
deny coverage if an arsonist starts a fire on the outside wall of a
building housing such work. Getting the thing inspected in small potatoes.
--
Tim Wescott
Wescott Design Services
http://www.wescottdesign.com
Posting from Google? See http://cfaj.freeshell.org/google/
"Applied Control Theory for Embedded Systems" came out in April.
See details at http://www.wescottdesign.com/actfes/actfes.html |
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mike.j.harvey@gmail.com
electronics forum beginner
Joined: 09 May 2006
Posts: 18
|
| Posted: Wed Jul 19, 2006 5:25 pm Post subject:
Re: Circuit design for 10.5 amp 230V 2HP motor @ 3450rpm
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Robert Latest wrote
| Quote: | In Europe, 3-phase 400V lines go into every
home.
|
No they bloody don't! European electricity supply undertakings are very
reluctant indeed to supply 3 phase power to anywhere other than
industrial and commercial users, where there is no alternative. In fact
you may as well say that domestic customers are limited to 230v single
phase.
However 415v three phase lines are buried in the street, and houses are
supplied from phase + neutral. |
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ehsjr
electronics forum Guru
Joined: 03 May 2005
Posts: 863
|
| Posted: Wed Jul 19, 2006 9:42 pm Post subject:
Re: Circuit design for 10.5 amp 230V 2HP motor @ 3450rpm
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|
TSL wrote:
| Quote: | OK, now were getting somewhere. Thank you Mr Walpert.
I am clear about the difference between the ground and nuetral in
general terms. What I am unclear about is why a 240V motor (which is
also on my compressor) does not need the nuetral? This is one of the
gaps in my understanding. It bugged me when I hooked up my compressor
but i just let it go. With what I am doing now, I'd really like to
understand why 240V seems to change the whole playing field and drops
the nuetral.
|
Perhaps a DC example would help.
View in fixed font
+----Hot-----+-------------+
+ | | |
---------- ------- |
|Battery 6V| |Bulb 6V| |
---------- ------- |
| | --------
+----nnnn----+ |Bulb 12V|
+ | | --------
---------- ------- |
|Battery 6V| |Bulb 6V| |
---------- ------- |
| | |
+----Hot-----+-------------+
For the purpose of the analogy, call the wire labeled nnnn
"Neutral". It is easy to see why it is needed - it makes
both 6V bulbs "happy". They get 6 volts each, and will
continue to work if the other 6V bulb burns out. They will
both glow at the proper level, even if the top one draws
7 amps and the bottom one draws 300 mA.
Eliminate the "neutral" wire and those 6 volt bulbs may have
a problem. For example, if there was no neutral and the top
one tried to draw 7 amps, it would have to draw it through
the bottom bulb. If that bulb was rated only for 300 mA, it
would burn out.
The 12 volt bulb doesn't need the neutral. It gets the proper
voltage from the two wires marked "hot" with no need for an
additional current path.
In your resisdence, the incoming 240 volts comes off a center
tapped transformer, anologous to the two batteries above.
Your 120 volt appliances are analogous to the 6V bulbs. Your
240 volt motor is analagous to the 12 volt bulb.
Ed |
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TSL
electronics forum beginner
Joined: 18 Jul 2006
Posts: 7
|
| Posted: Wed Jul 19, 2006 10:03 pm Post subject:
Re: Circuit design for 10.5 amp 230V 2HP motor @ 3450rpm
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mike.j.harvey@gmail.com wrote:
| Quote: | Robert Latest wrote
In Europe, 3-phase 400V lines go into every
home.
No they bloody don't! European electricity supply undertakings are very
reluctant indeed to supply 3 phase power to anywhere other than
industrial and commercial users, where there is no alternative. In fact
you may as well say that domestic customers are limited to 230v single
phase.
However 415v three phase lines are buried in the street, and houses are
supplied from phase + neutral.
|
OK great, we have established 3 phase power is not a European standard.
But this is moot to my issues.
I've still got 2 of my questions unanswered. Should I ask them in a
different forum than design? It's not that I don't appreciate the
involvment and time expended thus far, it's just that I need some
answers. The electrician at my work is Italian born and speaks English
with a classic, heavy Italian accent. He and I get along great. But
when I ask these particular questions, I don't seem to be communicating
well because he looks at me with some confusion - plus he talks fast
when he gets going. I'm not going to have an inspector come out in the
very sprawled and busy county I live in just so I can get some
questions answered. I would rather wait until I get it all done and
respect his time.
So I still need help. If this is the wrong venue, please point me to
the correct one
Thanx.
TSL |
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TSL
electronics forum beginner
Joined: 18 Jul 2006
Posts: 7
|
| Posted: Wed Jul 19, 2006 10:12 pm Post subject:
Re: Circuit design for 10.5 amp 230V 2HP motor @ 3450rpm
|
|
|
ehsjr wrote:
| Quote: | Perhaps a DC example would help.
View in fixed font
+----Hot-----+-------------+
+ | | |
---------- ------- |
|Battery 6V| |Bulb 6V| |
---------- ------- |
| | --------
+----nnnn----+ |Bulb 12V|
+ | | --------
---------- ------- |
|Battery 6V| |Bulb 6V| |
---------- ------- |
| | |
+----Hot-----+-------------+
For the purpose of the analogy, call the wire labeled nnnn
"Neutral". It is easy to see why it is needed - it makes
both 6V bulbs "happy". They get 6 volts each, and will
continue to work if the other 6V bulb burns out. They will
both glow at the proper level, even if the top one draws
7 amps and the bottom one draws 300 mA.
Eliminate the "neutral" wire and those 6 volt bulbs may have
a problem. For example, if there was no neutral and the top
one tried to draw 7 amps, it would have to draw it through
the bottom bulb. If that bulb was rated only for 300 mA, it
would burn out.
The 12 volt bulb doesn't need the neutral. It gets the proper
voltage from the two wires marked "hot" with no need for an
additional current path.
In your resisdence, the incoming 240 volts comes off a center
tapped transformer, anologous to the two batteries above.
Your 120 volt appliances are analogous to the 6V bulbs. Your
240 volt motor is analagous to the 12 volt bulb.
Ed
|
FANTASTIC - thanx Ed. One down. Two more to go - care to take a whack
at my motor starter & brake issue, Ed?
TSL |
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