Ummmm..no.
With proper gearing, you can prob get a car to 70 with a washing machine motor....but thats not the point. Your analogy is flawed in the fact that an electric motor, in the case we are talking about, runs at, and Im using your example here, at WOT all the time, limited in final RPM by blade pitch and load. Your car example, has a variable speed control...your foot.
But a 1 hp motor capable of running a given fan blade at 1000 rpm is running at 1000 rpm. A 2 hp motor with the same fan blade mounted running at 1000 rpm is till running at 1000 rpm. The fact that is has more HP does not make it turn faster.
Are you asking or telling? Cause if your asking I'm ready to post a few hundred web pages that will explain it to you. If you're telling then you should probably stop telling and do a little more homework.
hvacrmedic
I'm always looking to learn.
Man..Ed is a pretty good guy..and hes right, hes willing to learn. Hell, if you had told me that 12 years ago, i would have laughed at you...then, I got to learn all about swamp coolers and what 1/3 HP more or less can do....:)
>
I'll agree with you about Ed, but his replies in this thread seem to be a bit uncharacteristic of him. I'm only suggesting that if he doesn't trust what I said, then he might want to hit Google up about it ;)
hvacrmedic
This is Turtle.
I always want someone to tell me something that i did not know but here you are mistaken as to right or wrong.
Go back and read what Ed wrote here and tell or explain to me what is false about what he wrote and not say i have all these book to let you read to learn something. You or CB can't punch any holes in what he said at all and as it seem tring to dodge the question as to answer his statement as what is wrong with it.
Richard , have you been drinking something ?
TURTLE
This is Turtle.
Damn your good CB !
Now explain what is wrong with Ed's post besides asking you for a straight answer.
TURTLE
Start here:
"[...]Actual RPM for an induction motor will be less than this calculated synchronous speed by an amount known as slip that increases with the torque produced. With no load the speed will be very close to synchronous. When loaded, standard motors have between 2-3 percent slip, special motors may have up to 7 percent slip, and a class of motors known as torque motors are rated to operate at 100 percent slip (0 RPM/full stall).
The slip of the AC motor is calculated by:
S = (Ns - Nr) / Ns
where
Nr = Rotational speed, in revolutions per minute. S = Slip, in percent.
As an example, a typical four-pole motor running on 60 Hz might have a nameplate rating of 1725 RPM at full load, while its calculated speed is
1800."_______________________
If you didn't believe me, then maybe you can believe the above. Happy reading! It really is an excellent article, I recommend it to anyone who deals with motors on a regular basis. Also good reading for those who only want to learn about them. Now pardon me while I take time to read the rest of it :)
hvacrmedic
Congrats Turtle, your at the end of your rope. :)
hvacrmedic
This is Turtle.
Yes i can see where I'm not the suck up type and would not ask you question that any normal suck up would ask , but i see you and CB are dodging the bullet on answering Ed's Question for if you do you will be covering up a bullshitting line that got out of hand. So you two will take the 5 th on this one for if you answer , you will step off in it.
Now i'm going to ask you the querstion of this : Richard , what is wrong with ed's post above here and explain to me how or what is wrong with it and not just go get some books and find out. If you knew you could explain it in 1 or 2 line and it's all over. if you don't say anything i will take it as just running from a bullshit that got out of line. it hurts to cut and run don't it !
TURTLE
Learn to read and you will find out I did.
Tell another lie Terry..we got ya in a couple now.
>
Actually, hackboi, you ahve explained this one before....funny how the right answers seem to leave you when you are on a trolling spree.
I've answered it three times now. Hell I had to answer the last one 12 f****ng times and you still didn't get it. Are you kin to Marcell Ledbetter? Hooooeey!
hvacrmedic
This is Turtle.
i know what your hitting at here and you have pushed your motor theory too far to accept here.
If you have a 1 h.p. motor 1075 rpm, running at 1075 rpm on a 1 horse load. Then you take a 2 horse 1075 rpm motor and replace the one horse motor with the 2 h.p. motor 1075 rpm . the 2 h.p. motor will pull the load well at maybe 1075 to 1085 , but no where near 1200 rpm. now leave power factors out of it here.
Now you say a 1 hp motor 1075 rpm job when replaced with a 2 horse motor 1075 rpm , the motor will turn at maybe 1,200 rpm or better.
Now you may have got your info from Nick Pines but in the real world the single speed condenser motor 1075 1/3 hp. will turn at 1075 at 1/3 hp load. if you increase the horse power two times will not increase the speed any great amount to speak of or about maybe 10 rpm's at best because of a 1/3 hp load and a 2/3 hp motor pulling it.
Now you say a 4 speed indoor blower will spend at 1,200 rpms if on high and on low and other speeds it will run slower because of slippage of the motor and make it turn at say 800 rpms.
If this is true and lower speed and all other speeds turn at 1200 rpm always if unloaded. Why do they have 4 wires on it and just have 2 and just let it slip for the other lower speeds.
Probley what your tring to use for a example is the new multi-horse power & speed motors. With these they may have this theory but regular motor don't follow your thinking.
I know a fellow at emerson and i will tomorrow to check with him and check your NEW theory out. I've heard it before and it did not flow.
TURTLE
This is Turtle.
Please Point to it or tell me where you explain this to me ?
TURTLE
OK.
/\\ / \\ / \\ | | | |
hvacrmedic
This is Turtle.
OH MY GOD , Tell me about what they are.
TURTLE
The trip saver is just a multi-tap motor. The main difference is that the HP of the highest speed on the trip saver can be adjusted by simply changing capacitor mfd rating. You can do the same thing with any other
4-speed blower motor, but you would need to know what you were doing, because the instructions won't be drawn out for you on a little piece of paper like it is with the trip saver. I doubt that any manufacturer would warranty a motor that had been field re-engineered, but that doesn't mean that it can't be done.Now as for your numbers, you should consult the motor's RPM/torque curve before attempting to post any numbers. Keep in mind that motors aren't all made equal. A PSC motor for instance, varies more in RPM through changes in torque than does an induction run motor in the same application. If you look at the rated RPM you can see the difference. A typical PSC with 1200RPM synchronous will typically be rated at 1050 or
1075RPM at full load. An induction motor OTOH might be rated at 1100 or 1150RPM. Both have the same synchronous (no load) RPM of 1200, but they will not run the same RPM with equal loads. The PSC will run slower.If you double the HP of the PSC you will get much more of an increase in RPM than you would by doubling the HP of an induction run motor. You won't however go above synchronous (rotating field) RPM regardless of how much you increase HP.
Don't beat yourself over the head too hard for missing this one, even Jake missed it a year or so back over in alt.hvac. I had to post motor curves and articles for him too, before he finally understood that I knew what the hell I was saying all along. :)
hvacrmedic
BTW, according to the formula above, a PSC motor rated at 1050 RPM at full load has a 12.5% slip. Assuming a nearly linear curve in the upper region of the motor curve, doubling the HP would result in a slip of approximately 6.25%, for a final RPM of approximately 1125. This is a
75 RPM increase. This may not seem like much, but the cfm increase due to this much increase in RPM will be substantial. It more than likely won't be an operational problem for the unit, but keeping the argument in context, it could very well lead to a coil freezing up that wasn't freezing before under the same ambient conditions, that is, when it was already cool outside and the coil was already near the freezing point. Is that understood, or would you like a bit more clarification. I can talk about this shit all day long :)hvacrmedic
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