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Discussion Starter · #1 ·
hey guys is it normal for the motor to have a certian amount of whine at high rpm's. My AMD fb4001 get's singin perty good at about 4-5 k ?( about 25-30mph in first gear, 120v) I do like the decreased draw at the higher rpm's and was demonstrating it to my wife who said " is that hurting to motor". I didn't think so but thought that I'd check. the driveline, otherwise is smooth, no grinding or binding noticed.
 

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hey guys is it normal for the motor to have a certian amount of whine at high rpm's. My AMD fb4001 get's singin perty good at about 4-5 k ?( about 25-30mph in first gear, 120v) I do like the decreased draw at the higher rpm's and was demonstrating it to my wife who said " is that hurting to motor". I didn't think so but thought that I'd check. the driveline, otherwise is smooth, no grinding or binding noticed.
Hi ace,

Certain amount of whine at 4 to 5krpm? I'd say yes. You have brushes sliding around on the comm and that will make a whine. Is what you hear abnormal??? Can't tell from this far away :) Has it gotten worse? Is the motor relatively new? Does it have a nice patina on the comm surface? Do either of the bearing housings get much hotter than the rest of the motor?

It could be all right, could get better, or could be something to worry about. I'd keep an eye, or ear on it. And I think it would be O.K. to up shift and run the motor down around 3 to 3.5krpm. It should not change your battery current draw. It will increase motor current, but I would think still be in the allowable range.

Regards,

major
 

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Discussion Starter · #3 ·
Hi ace,



Certain amount of whine at 4 to 5krpm? I'd say yes. You have brushes sliding around on the comm and that will make a whine. Is what you hear abnormal??? Can't tell from this far away :) Has it gotten worse? Is the motor relatively new? Does it have a nice patina on the comm surface? Do either of the bearing housings get much hotter than the rest of the motor?

It could be all right, could get better, or could be something to worry about. I'd keep an eye, or ear on it. And I think it would be O.K. to up shift and run the motor down around 3 to 3.5krpm. It should not change your battery current draw. It will increase motor current, but I would think still be in the allowable range.

Regards,

major
#1 gotten worse, no. motor is new, bearings hot? not that I've noticed! nice patina on the comm, surface? I have no idea what this means please explain! so your saying that even though i notice the amperage goes down and the voltage comes up at highter rpms vs lower rpms I'm not using less current? thanks again
sorry I can't figure out how to quote on this site!
 

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#1 gotten worse, no. motor is new, bearings hot? not that I've noticed! nice patina on the comm, surface? I have no idea what this means please explain!!
O.K. ace,

First off, we are not sure the whine is coming from the commutator. But if it is, then consider the following.

It has not gotten worse and motor is new. I assume you did not break in the motor. That would be to run to condition the commutator. The commutator needs to have a film of carbon from the brushes in order to function properly and get best performance in regards to voltage drop and friction. This film is sometimes called patina.

Commutator Appearance Guide
In addition to the physical appearance of the surface of the commutator, the skin or patina (film) is of equal importance for the good running of the carbon brushes. Each carbon brush builds a characteristic patina (film) which is affected by operating and ambient conditions. The patina (film) consists mainly of copper oxides, graphite deposits and absorbed water, and its appearance is of importance for the assessment of the running behavior of the commutation set. The following pictures are used by carbon brush manufacturers and users of brushes as a guide to assist in judging the operation of carbon brushes.
The pictures didn't paste in here, so go to http://www.gulfelectroquip.com/technical.php?technicalname=commutator to see the photos.

Without this proper film the brushes may make excessive noise, like fingernails on a blackboard.

so your saying that even though i notice the amperage goes down and the voltage comes up at highter rpms vs lower rpms I'm not using less current?
For the same conditions and the same vehicle speed you require the same power which comes from your battery regardless if you're in 2nd or 3rd gear, so the battery voltage and battery current will be the same (or within a few percent). Now you have a difference in gear ratios so the motor RPM will be different at that same vehicle speed between 2nd and 3rd gear. So the motor controller will alter the voltage current relationship between the battery and motor. In 3rd gear, the motor will have lower RPM, lower voltage and higher current, but the battery voltage and current will be the same as it was in 2nd.

Are you monitoring battery volts and amps? If so, do a simple test. Flat road, no wind, drive steady 25 mph in 2nd. Record battery V & I. Shift to 3rd, let it steady out at 25 mph, will be the same battery V & I. Make sure your speed is steady, not accelerating or decelerating or any grade (hill) changes.

See if you can verify where the whine is originating. And take a look at the comm. See if it is better with lower motor RPM.

Regards,

major
 
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