🚀 go-pugleaf

In article <jkemp.23@bss1.umd.edu> Joe Kemp, jkemp@bss1.umd.edu writes:
>
>	I have a standard blow with a standard 115V single phase "four 
>speed" motor on it.  The label on the motor says it is a 1050RPM motor
with 
>four speeds.  The problem is that all four speeds are about the same.  
>My questions are as follows:
>
>	1.  If label RPM is 1050 what are the other 3 speeds, higher, lower 
>            on each side or what?
>
>	2.  I thought motors come in 1050, 1175 or 3000 something, other 
>	    speeds were gotten with a rheostat or pulley system...
>
>
>Anyhelp would be appreciated...
>
>jkemp@bss1.umd.edu  
The motor you discribe is propably a 6 pole, 60 Hz high slip induction
motor. At the high speed position it will run at 1050 rpm when it is
loaded at its rated load. (Which for a forced air furnace fan is
typically 1/5, 1/4, or 1/3 hp). The speed adjustments will typically
reduce the speed to about 700 rpm at the low speed. This is done by
disconnecting some of the coils of wire in the motor and thus increasing
the slip. (for this motor slip=(1200-speed)/1200)

Your problem sounds similar to one I have with my furnace fan. I have a
1/3 hp motor, but it takes far less then 1/3 hp to turn the fan.
Therefore the motor runs close to its synchronous speed (1200 rpm). The
speed adjustments will change the slip of the machine by aproximatly a
fixed %. With the motor running close to 1200 rpm the slip is small (0.05
for 1140rpm), so the resulting speed change is small (but if you use a
strope light, as I did, you will see it change) At rated load the slip is
much higher (0.125 in your case) The same % change in this larger number
will produce a speed change which is noticable. 

In your case, I suspect your blower is turning at about 1100-1150 rpm
because the motor is to powerful. Solutions are 
	1.) buy different pulleys (smaller on the motor, larger on the blower)
	    This won't work if it is direct drive.
	2.) buy a smaller hp motor (if you have 1/3 hp, you ussaly can find a 
          1/5 hp which is the same physical size so that you don't have
to 
          change any mounting hardware)
	3.) reduce the operating volatge (not a very practicle solution)