Electric Motor noise

[mayday0017]

I noticed the other day when I was in a tire shop that they had a very simular compressor to mine. Both are the same brand (speedaire) both had the same Champion pump. Their setup had 2 pumps and 2 motors on the same tank was the only difference. I would also guess they had 2 5hp motors and not 2 7.5hp motors.

So what else I noticed is theirs kicked on and was quiet enough you could carry a conversation. Mine is a 7.5hp unit (and think it spins a little faster) and mine is 100% factory origional. But mine sounds like some heavy duty electrical piece of equipment when it runs. The electrical sound from the motor is louder then the pump I think.

So this made me wonder.... could there be something wrong with my motor? Does a motor that has insufficiant power from to small of wiring make noise? I am grasping for ideas, if it is normal for a 7.5hp motor to have an industrial electric sound to it that is fine. But if my motor is struggling for power or something isn't right I want to correct it before I end up having to buy a whole new motor. 7.5hp single phase motors are not cheap!

 

[A_Pmech]

Three phase motors usually start more quietly than comparable single-phase motors.

 

[G_P]

The shops compressor may be running 1750rpm motors where yours may be 3500rpm. That would make a huge difference in the sound level.

A motor running by itself though should not make that much of a racket.

 

[mayday0017]

This is a good point, I'm not sure what the motor RPM is on my compressor but the pump RPM is 1035. The noise that I am talking about is not made by the pump though (really the pump noise between the two sounded the exact same) but it is rather an electrical noise... Trying to think of something to compair it to, best I can think of is a huge turbine generater in a Dam or something.

Here is the information on my compressor
http://www.grainger.com/product/SPEEDAIRE-Electric-Air-Compressor-1WD61

 

[mayday0017]

Also just guessing from the way it looked and my assumption they have a 5hp model their pumps are turning at 760rpm

Here is a link to the specs of what I assume their compressor is by appearance only.
http://www.grainger.com/product/SPEEDAIRE-Electric-Air-Compressor-4XA67?functionCode=P2IDP2PCP

 

[sands35]

Check and see if there are loose bolts, obvious misalignment in the pulleys or a cracked motor base foot or something.

Then don't worry about it.

 

[G_P]

Can you take the belts off and make a short video of the motor running with no load on it? It may have a failing bearing as that can make some noise.