Motor Load vs HP vs Current
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From: JosephKK on 30 Jul 2010 23:02 On Sat, 24 Jul 2010 11:20:38 -0700 (PDT), Bobby Joe <bobbyjoe23928(a)gmail.com> wrote: >On Jul 24, 12:29�pm, Tim Wescott <t...(a)seemywebsite.com> wrote: >> On 07/24/2010 10:03 AM, Jamie wrote: >> >> >> >> > Bobby Joe wrote: >> >> >> If I have a motor that is being overloaded ~2x it's rated will >> >> doubling the HP improve this? >> >> >> I have a 1/2HP Direct drive 1P, 120V, 1075RPM blower motor that is >> >> drawing 12A while it is rated at 6.5A Full load, 9A max and only >> >> spinning at about 700RPM. [No load it draws 3A] >> >> >> The problem I was having is any time the AC kicked in I would lose >> >> connection to the net and the power would sag. I went to the attic and >> >> measured the AC and found it was drawing 2x the rated current at full >> >> load. I thought the motor was bad so I got an identical replacement >> >> but almost exactly the same measured specs and same problem. >> >> >> I figured I could replace it with a 3/4 or 1HP motor and get better >> >> results but I'm not sure how much. I want to save power and possibly >> >> increase the rpm's, >> >> >> The main thing I would like to know is how HP, current, and load are >> >> related. If I double the HP I should effectively be doubling the max >> >> load and probably the current at max load? Basically, if I have an x >> >> HP motor using a certain load and I move to y HP motor then what can I >> >> expect the RPM's and current to be? [simple estimates are ok. I >> >> understand that it depends on a lot of factors but there should be >> >> general principles involved] >> >> >> As I said, I would like to be able to determine if a 1HP is >> >> effectively going to allow me to increase the RPM's and reduce the >> >> current[since the motor shouldn't be overloaded]. >> >> >> Motor used, >> >> >>http://www.grainger.com/Grainger/AO-SMITH-Direct-Drive-Blower-Motor-4... >> >> >> Possible replacements, >> >>http://www.grainger.com/Grainger/DAYTON-Direct-Drive-Blower-Motor-4M1... >> >> >>http://www.grainger.com/Grainger/DAYTON-Direct-Drive-Blower-Motor-3LU... >> >> >> BTW, what is the difference between a Y and YZ frame? >> >> >> Thanks for the help, >> >> Bob >> >> > Did you replace or test the Capacitor ? Those motors like cooking the >> > caps that come with them.. Made in Mexico! also, the bearings are >> > crappy! Make sure you are not voltage sagging at the leads. >> >> > Also, have you pull the motor out in the open with blades on and tested >> > the load? You could have a restricted vent some where. That does not >> > sound normal.. >> >> Some blowers load the motor more heavily when the duct work isn't >> restricted -- have you ever noticed how your vacuum cleaner speeds up >> when the intake is clogged? > >The AC unit is not a vacuum cleaner. It is much much bigger. The ducts >are 2 feet wide and node 2 inches. I don't know what you think could >be clogging up the ducts but it seems you've never done much air duct >worked for central heat and air as then it should be pretty obvious. > >> I don't think this is a problem with the motor, assuming that it is the >> correct motor for the blower. > >That's a big assumption. The motor is drawing 12A simple as that. The >only way it can draw this much current is if it is suppose to or if it >is overloaded. > Which immediately generates the questions of why and how?
From: gerry on 31 Jul 2010 12:24 [original post is likely clipped to save bandwidth] On Sat, 24 Jul 2010 09:18:14 -0700 (PDT), Bobby Joe <bobbyjoe23928(a)gmail.com> wrote: >If I have a motor that is being overloaded ~2x it's rated will >doubling the HP improve this? > >I have a 1/2HP Direct drive 1P, 120V, 1075RPM blower motor that is >drawing 12A while it is rated at 6.5A Full load, 9A max and only >spinning at about 700RPM. [No load it draws 3A] > >The problem I was having is any time the AC kicked in I would lose >connection to the net and the power would sag. I went to the attic and >measured the AC and found it was drawing 2x the rated current at full >load. I thought the motor was bad so I got an identical replacement >but almost exactly the same measured specs and same problem. Is this a motor problem or a supply problem? A 9A load should not sag your mains such that other equipment (net) fails. Did you measure RMS current? Peak (common) are misleading. What was the voltage at the motor and at your mains? Low voltage can cause high currents. In computer electronics, peak voltage is usually more important than RMS. gerry > >I figured I could replace it with a 3/4 or 1HP motor and get better >results but I'm not sure how much. I want to save power and possibly >increase the rpm's, > >The main thing I would like to know is how HP, current, and load are >related. If I double the HP I should effectively be doubling the max >load and probably the current at max load? Basically, if I have an x >HP motor using a certain load and I move to y HP motor then what can I >expect the RPM's and current to be? [simple estimates are ok. I >understand that it depends on a lot of factors but there should be >general principles involved] > >As I said, I would like to be able to determine if a 1HP is >effectively going to allow me to increase the RPM's and reduce the >current[since the motor shouldn't be overloaded]. > > >Motor used, > >http://www.grainger.com/Grainger/AO-SMITH-Direct-Drive-Blower-Motor-4KA36?Pid=search > >Possible replacements, >http://www.grainger.com/Grainger/DAYTON-Direct-Drive-Blower-Motor-4M183?Pid=search >http://www.grainger.com/Grainger/DAYTON-Direct-Drive-Blower-Motor-3LU91?Pid=search > >BTW, what is the difference between a Y and YZ frame? > >Thanks for the help, >Bob -- Personal home page - http://gogood.com gerry misspelled in my email address to confuse robots
From: Michael A. Terrell on 2 Aug 2010 09:39 ..p.jm.(a)see_my_sig_for_address.com wrote: > > Click here every day to feed an animal that needs you today !!! > www.theanimalrescuesite.com/ Click WHERE? All I see is plain text. If you want a link that works for everyone, you need to prefix the text with http:// Like this: http://www.theanimalrescuesite.com
From: Real Pisser on 2 Aug 2010 09:59 "Michael A. Terrell" <mike.terrell(a)earthlink.net> wrote in message news:b-idnU9YhJ01V8vRnZ2dnUVZ_hudnZ2d(a)earthlink.com... > > .p.jm.(a)see_my_sig_for_address.com wrote: >> >> Click here every day to feed an animal that needs you today !!! >> www.theanimalrescuesite.com/ > > > > > > > > > Click WHERE? All I see is plain text. If you want a link that works > for everyone, you need to prefix the text with http:// > > Like this: http://www.theanimalrescuesite.com The link (Paul's), works fine for me. I click it several times a week, as we care for animals too. I am using IE8 as a browser. sometimes with IE8, the http:// prefix causes problems; go figure! easy enough to overcome either way. --- news://freenews.netfront.net/ - complaints: news(a)netfront.net ---
From: Steve on 4 Aug 2010 10:28
"Bobby Joe" <bobbyjoe23928(a)gmail.com> wrote in message news:f4495dba-62d3-4a83-93d7-6b91f0b58834(a)f6g2000yqa.googlegroups.com... > If I have a motor that is being overloaded ~2x it's rated will > doubling the HP improve this? > > I have a 1/2HP Direct drive 1P, 120V, 1075RPM blower motor that is > drawing 12A while it is rated at 6.5A Full load, 9A max and only > spinning at about 700RPM. [No load it draws 3A] > > The problem I was having is any time the AC kicked in I would lose > connection to the net and the power would sag. I went to the attic and > measured the AC and found it was drawing 2x the rated current at full > load. I thought the motor was bad so I got an identical replacement > but almost exactly the same measured specs and same problem. > > I figured I could replace it with a 3/4 or 1HP motor and get better > results but I'm not sure how much. I want to save power and possibly > increase the rpm's, > > The main thing I would like to know is how HP, current, and load are > related. If I double the HP I should effectively be doubling the max > load and probably the current at max load? Basically, if I have an x > HP motor using a certain load and I move to y HP motor then what can I > expect the RPM's and current to be? [simple estimates are ok. I > understand that it depends on a lot of factors but there should be > general principles involved] > > As I said, I would like to be able to determine if a 1HP is > effectively going to allow me to increase the RPM's and reduce the > current[since the motor shouldn't be overloaded]. > > > Motor used, > > http://www.grainger.com/Grainger/AO-SMITH-Direct-Drive-Blower-Motor-4KA36?Pid=search > > Possible replacements, > http://www.grainger.com/Grainger/DAYTON-Direct-Drive-Blower-Motor-4M183?Pid=search > http://www.grainger.com/Grainger/DAYTON-Direct-Drive-Blower-Motor-3LU91?Pid=search > > BTW, what is the difference between a Y and YZ frame? > > Thanks for the help, > Bob > Check to make *sure* that you have not got any air flow restriction issues...... excessively restrictive filter, registers closed, dirty evap coil, insulation that came loose inside the plenum, etc. BTW... when you did the amp draw and rpm measurements, did you have the cover off the blower compartment?? Gotta love it when an EE plays with stuff. :-) |