# Dc Motor Hum.....



## calstar (May 30, 2016)

Just installed this motor on my 1987 12x36 jet using a Minarik controller, drive belts not on so its not running  under load. With power the motor runs smooth but hums quite loudly(gotta be louder than usual, never run a DC motor before) and smells a little hot(not to touch and no magic smoke escaping). Ive had the motor a couple of years but only ran it when testing  the mill it came on, I don't remember it making any noise then but it was a while back, memory banks lacking on this one. Checked the brushes they're in good shape, not much wear, thats about all I know what to look at.  If anyone can help me try to figure it out I'd really appreciate  it.

thanks,   Brian


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## TOOLMASTER (May 30, 2016)

do you have the field wires and armature wires hooked up..4 total


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## TOOLMASTER (May 30, 2016)

btw they do hum...mainly because it is not true dc like from a battery


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## calstar (May 30, 2016)

_Toolmaster_, yes both the field and armature wires are connected to the controller. I don't know if its more of a hum than buzz but the noise is constant regardless of the motor rpm as controlled by the controller. I did a google search before posting this and found quite a lot about DC motor hum/buzz but sorta hard to wade through it all with my level of knowledge. I'm going to double check the controller connections as per instructions and see if I did something wrong.

Thanks, Brian


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## TOOLMASTER (May 30, 2016)

arm an field reversed maybe?


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## John Hasler (May 30, 2016)

The hum should not be loud and the motor should not get hot with no load.


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## calstar (May 30, 2016)

Yep, all connected as per instruction/wiring diagram.  Here is something I just heard, without touching/moving the speed pot dial the *rpm appears to be pulsing*, not continuous but every 5 seconds or so.  I have  the pot mounted in a junction box and when mounting it I dropped the box twice; maybe the pot got screwed up and is not sending a clean signal(if that makes sense)? There's a Radio Shack a mile from me, I think I'll get a new pot and see if thats it(when in doubt switch parts, right?). The hum is the same when I switch motor rotation by changing the armature leads on the controller.

The noise is loud enough to hear it across my garage/shop but its the smell that concerns me; although there is not visible smoke I have a slight headache from sticking my head close to the motor (not doing that anymore!!) so something is wrong.

Brian


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## Ulma Doctor (May 30, 2016)

i'd suspect a controller fault, there should be no loud humm


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## TOOLMASTER (May 30, 2016)

could be the settings inside the control box...if not set right the motor will pulse


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## TOOLMASTER (May 30, 2016)

do you have a pic of the controller.


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## calstar (May 30, 2016)

Found a few things on this site, seems like a good info source:
https://www.americancontrolelectronics.com/t-faq.aspx#tech1       ( formerly Minarik)

_*Why is my motor producing a loud humming/buzzing sound?*
If the motor is producing this type of sound, a non-filtered SCR type drive is probably being used to run it. SCR type drives pulse a motor with voltage 120 times per second. The sound that is heard is the magnetic fields energizing and breaking down inside the motor at 120Hz. Although this is normal, a PWM type drive is a good choice if the hum is not acceptable in the application.

*What is a line filter?*
A line filter is a device typically connected in between the AC line source and the input of a drive. A line filter is designed to prevent electrical noise from entering a drive. Line filters are commonly used in applications where electrical noise is generated, such as in welding applications. SCR type drives are most commonly affected by line noise due to their reliance on a clean AC waveform for switching purposes._


The drive is SCR type, I have an AC line filter from a treadmill, it may help with the pulsing/oscillating, yes?


_*Why does my motor oscillate / not run smoothly?*_

_*IR Comp Adjustment*: Most drives have this adjustment.* If set too far clockwise the motor will tend to oscillate*. Slowly turn the IR Comp trim pot in the counter clockwise direction until the oscillation stops._
_Speed command signal: *An unstable speed command signal to the drive can cause the motor not to run smoothly. Remove the command signal from the drive and use a potentiometer instead*. If the motor becomes smooth, the external speed command signal was the source of the problem.          _
_Change in load: In most applications a drive can be tuned to run a motor smoothly and compensate for changes in load. But when loads change abruptly, the IR Comp circuit cannot respond fast enough. Make sure there are no mechanical problems in the operation that can cause these abrupt changes in load. A good way to check this is to simply remove the load from the motor and observe how it runs. If operation becomes smooth, you most likely have a mechanical obstruction._
_Motor brushes: If using a permanent magnet motor, inspect the brushes for excessive wear or irregular wear. It also a good idea to blow compressed air into the brush housing to clean out any carbon build up. If possible, turn the motor shaft as you blow compressed air into the brush compartment._
_Max speed too high: Having the output voltage to the motor set too high can cause some drives armature output to become unstable. Do not try to run a motor that exceeds the armature voltage that is available to use. For example, you can’t run a 180VDC rated motor when you power a drive with 115VAC.          _

#1     I'll try adjusting the IR comp as noted.
#2    Its running on a speed pot now so does this apply in some way?
#3    Not running under load
#4    Brushes look good, commutator(think thats right) is not shiny copper, maybe carbon build up from the brushes?
#5    I'm running on 230VAC

I'm off to do a little tweaking and take a few pics.

Brian


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## John Hasler (May 30, 2016)

Try backing off the IR comp.  The filter won't make any difference: it is mostly to prevent the controller from interfering with other stuff.  The commutator normally looks dull.


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## TOOLMASTER (May 30, 2016)

there are speed pots inside along with ir comp...acceleration..deceleration..min speed ..max speed..and one more that i cant think of right now...on most big controllers ..but you haven't posted a pic yet so everyone is just guessing


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## mattthemuppet2 (May 30, 2016)

I found adding a choke on one of the DC lines made a huge difference in hum on my lathe treadmill motor. I didn't realise what it was for until someone suggested adding it and I was glad I kept it on the shelf. I didn't have one for my second conversion (drill press) and it hums pretty loudly, so I ordered another choke off ebay for $14. I'll see if it makes a difference on this set up. Worth thinking about.


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## calstar (May 30, 2016)

Heres the pics, armature and field leads color codes so I can keep track  of them connecting to the controller. All connections are as per Minarik install instructions.  

I backed off the IR Comp and that got rid of the oscillation/pulse. I did notice that when the speed pot is turned all the way down but current still going through the hum is barley audible, I have to get my ear next to the motor to hear it. Also, if I back off the pot from full run in somewhat rapid steps the hum stops for just an instant as the speed decreases at each step, then starts again.  Maybe its OK, as stated before I don't know how loud a hum to expect, the smell seems to have lessened but still there.  Again, as posted above from the site:

_The sound that is heard is the magnetic fields energizing and breaking down inside the motor at 120Hz. Although this is normal, a PWM type drive is a good choice if the hum is not acceptable in the application.
_
The hum is acceptable, perhaps the smell is dust in the motor burning off from sitting for 2yrs......

thanks, Brian


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## TOOLMASTER (May 30, 2016)

is the min speed all the way down?


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## TOOLMASTER (May 30, 2016)

what do the tags say on the 2 brown wires?


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## TOOLMASTER (May 30, 2016)

with min pot at 0 and control knob at 0 hum should go away


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## TOOLMASTER (May 30, 2016)

is the speed control rated for the motor amperage...it is a small controller


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## calstar (May 30, 2016)

mattthemuppet said:


> I found adding a choke on one of the DC lines made a huge difference in hum on my lathe treadmill motor. I didn't realise what it was for until someone suggested adding it and I was glad I kept it on the shelf. I didn't have one for my second conversion (drill press) and it hums pretty loudly, so I ordered another choke off ebay for $14. I'll see if it makes a difference on this set up. Worth thinking about.



Didn't know what a choke is, looked at wiki:

_In electronics, a *choke* is an inductor used to block higher-frequency alternating current(AC) in an electrical circuit, while passing lower-frequency or direct current (DC). A choke usually consists of a coil of insulated wire often wound on a magnetic core, although some consist of a donut-shaped "bead" of ferrite material strung on a wire. The choke's impedance increases with frequency. Its low electrical resistance passes both AC and DC with little power loss, but it can limit the amount of AC due to its reactance._

How do I size/select a choke?

thanks, Brian


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## mattthemuppet2 (May 31, 2016)

calstar said:


> Didn't know what a choke is, looked at wiki:
> 
> _In electronics, a *choke* is an inductor used to block higher-frequency alternating current(AC) in an electrical circuit, while passing lower-frequency or direct current (DC). A choke usually consists of a coil of insulated wire often wound on a magnetic core, although some consist of a donut-shaped "bead" of ferrite material strung on a wire. The choke's impedance increases with frequency. Its low electrical resistance passes both AC and DC with little power loss, but it can limit the amount of AC due to its reactance._
> 
> ...



that's a great question! no idea  i used the one that came with an old treadmill and the one i just bought works with treadmills that have a similar hp motor. other than that hopefully an electrically competent member will chime in!


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## chips&more (May 31, 2016)

mattthemuppet said:


> I found adding a choke on one of the DC lines made a huge difference in hum on my lathe treadmill motor. I didn't realise what it was for until someone suggested adding it and I was glad I kept it on the shelf. I didn't have one for my second conversion (drill press) and it hums pretty loudly, so I ordered another choke off ebay for $14. I'll see if it makes a difference on this set up. Worth thinking about.


Was the choke used in the field or armature circuit? I think I can answer it myself and say the armature? Thanks in advance…Dave.


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## mattthemuppet2 (May 31, 2016)

there are 2 wires going to my motor, + and - . it's in series with the - wire, although i was told it doesn't make any difference which wire it's on.


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## John Hasler (May 31, 2016)

mattthemuppet said:


> that's a great question! no idea  i used the one that came with an old treadmill and the one i just bought works with treadmills that have a similar hp motor. other than that hopefully an electrically competent member will chime in!


You probably want a choke with an inductance between 2 and 3 millihenries.  The exact optimum value depends on the hp (more power->less inductance) and the controller design,  It isn't critical to get it exactly right.  The choke must be rated for the full load motor current.


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## chips&more (May 31, 2016)

mattthemuppet said:


> there are 2 wires going to my motor, + and - . it's in series with the - wire, although i was told it doesn't make any difference which wire it's on.


 OK, thanks, it’s on the armature circuit then. Your motor has real magnets for the field, so that’s why you only have two wires.


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## calstar (May 31, 2016)

Minarik 23001C specs






TOOLMASTER said:


> is the min speed all the way down?





TOOLMASTER said:


> what do the tags say on the 2 brown wires?





TOOLMASTER said:


> with min pot at 0 and control knob at 0 hum should go away





TOOLMASTER said:


> is the speed control rated for the motor amperage...it is a small controller



Brown tags are A1 and A2,  controller is well within spec for this motor(see above), I may try adjusting the other pots. I'm calling Minarik tech later today, I'll post any pertinent info(i.e. chokes)

Link to more info on the controller and calibrations;
https://www.minarikdrives.com/documents/250-0387.pdf

I love projects like these, I start out knowing next to nothing about DC motors and drives and now I know a little bit more than next to nothing!!
Thanks to all that posted here, most likely others can benefit from the shared knowledge,

Brian


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## TOOLMASTER (May 31, 2016)

once you put a load on you will have to re-adjust


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## TOOLMASTER (May 31, 2016)

looking at your picture is the 90-180 switch all the way left?


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## calstar (May 31, 2016)

_looking at your picture is the 90-180 switch all the way left?
_
No, ll the way to the right for 180VDC




John Hasler said:


> You probably want *a choke with an inductance between 2 and 3 millihenries*.  The exact optimum value depends on the hp (more power->less inductance) and the controller design,  It isn't critical to get it exactly right.  The choke must be rated for the full load motor current.



FYI anyone




Brian


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## calstar (May 31, 2016)

Spent about 20min on the phone today with a Minarik tech troubleshooting the controller with multimeter in hand, appears to be....... *a bad controller*! I had him listen to the hum on the phone, not good, as well as the fact that the inhibitor is not cutting current from the motor. He told me to contact Galco(vendor), send it back, get a new one and a refund for the bad one, they pay shipping both ways. I'll see how it all plays out but so far no problems setting it straight.

  Brian


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## TOOLMASTER (May 31, 2016)

that's what i meant..lol....just looked 1/2 way..



calstar said:


> _looking at your picture is the 90-180 switch all the way left?
> _
> No, ll the way to the right for 180VDC
> 
> ...


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## markba633csi (Jun 13, 2016)

One note: AFIK chokes are mainly used on PWM style mosfet controllers like those on treadmills. I don't think SCR units normally need them.  SCR units are generally hummy but yours may be bad. 
Mark S.


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