Motor Load vs HP vs Current
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From: Tony Hwang on 25 Jul 2010 11:27 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-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 > Hi, Was the motor working normal before? If answer is yes, either you have bad cap. or dying motor motor. Over or under rated motor has poor efficiency. RPM is pretty steady at rated independent of Hp.
From: Tony Hwang on 25 Jul 2010 11:31 Bobby Joe wrote: > On Jul 24, 12:03 pm, Jamie > <jamie_ka1lpa_not_valid_after_ka1l...(a)charter.net> 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.. > > Of course. The capacitor was good. Everything is fine except the > motor. I took the blower out of the duct so none of that is an issue. > It is simply an overloaded motor. This was probably done intentionally > to cut costs. From what I have read most motors are underrated > anyways. This motor has been drawing 12A for about 10 years and hasn't > burned up yet so it's max current is a bit conservative. > > The real question I had was not about what I have done but about the > relationships between HP, rpm, and current. It seem Paul was the only > one that got that. > > Hi, Brand name of the motor? Sounds like El Cheapo. Decent blower motors are actually under rated.
From: Stormin Mormon on 25 Jul 2010 14:35 Sure, if the voltage is too LOW, the motor won't run EFFICIENTLY. Yes, EFFICIENTLY. -- Christopher A. Young Learn more about Jesus www.lds.org .. "Mark" <makolber(a)yahoo.com> wrote in message news:ebae905e-e643-4934-bdd5-1622554cda04(a)w30g2000yqw.googlegroups.com... or the Voltage at the motor is too LOW, yes LOW.. Mark
From: Stormin Mormon on 25 Jul 2010 14:36 I've seen service panel problems. It sounds like good advice, to check the panel box. Look for white corrosion, or dark burnt areas. If you find either, call a licenesed electrician. -- Christopher A. Young Learn more about Jesus www.lds.org .. "The Daring Dufas" <the-daring-dufas(a)peckerhead.net> wrote in message news:i2garl$5ue$1(a)news.eternal-september.org... It sounds like you have an electrical supply problem and you're chasing butterflies. You mentioned losing connection to the net, I would assume you're referring to your Internet connection and the power to the whole house is sagging. If that's the case, your problem may be in your main electrical panel. It's not unusual for loose connections in main electrical panels to burn up in hot weather when heavy loads from AC systems stress them to the braking point. I would start at the main electrical panel first and inspect ALL of the connections and circuit breakers related to your AC unit. I've traced many AC problems back to the electrical service. TDD
From: tm on 25 Jul 2010 15:38
"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? > Since you are seeing a sag in the voltage, maybe the wiring is inadequate for the blower. Low voltage will cause an increase in current. Putting a larger motor in will increase the current. Have you measured the voltage at the motor? t --- news://freenews.netfront.net/ - complaints: news(a)netfront.net --- |