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Motor spluttering at low speeds

sniper123

Oct 31, 2013
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Hi, I have a motor from a Kenwood chef food mixer which I have recently replaced the capacitors, resistors and the triac to the same as original manufacture.

The issue is that when the motor dial is at minimum, the mixer motor, splutters, whereas upon turning it up, the splutter disappears.

The armature and brushes are fine and there is no end float on the armature.

I am wondering if I change the 220Ohm resistor for a smaller value, obviously to let more power thru', would this remove the splutter, due to my thinking that it's splutter due to lack of power getting thru'.

Point to note, this motor has contact point like in a old car engine.

The points are ok without any pitting or metal transfer.
 

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sniper123

Oct 31, 2013
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Hi, sorry about the upload, if you require a clearer picture, send me your email.

Regards
 

shrtrnd

Jan 15, 2010
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I'd be looking at the dial. Whatever your controller is, a potentiometer probably.
I know you said all the contacts you can see are clean. This sounds to me, like
dirty or worn contacts inside your dial controller, which I think would be a rheostat or
potentiometer. Have you looked at what your dial controller knob is connected to?
Sometimes you can clean contacts inside that.
 

sniper123

Oct 31, 2013
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Hi, the motor is a governor control type. The speed control dial does not have any components. The speed knob has a cam behind it, which moves the motor board up and down, this moves the governor to increase/decrease the speed.
 

Hopper

Oct 31, 2013
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Hi Sniper123,
It sounds to me like you are on the right track with the power. Is there any adjustment on the triac? We use them at work to control the speed of our motors and they all have a small grub screw in the back to adjust the "low stop point".
If we forget to do this then the motors will splutter, stall and sometimes arc.
 

sniper123

Oct 31, 2013
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Hi, no adjustment on the triac, its just a normal 3 legged one, this is why i am asking about reducing the size of the 220ohm down, let let more 'juice' thru.

The board has 2 screws which can be adjusted to increase/decrease the speed, but if I alter these, the low speed increases and I lose it off the top end, the dial has speeds 1-8, by adjusting the top end speed would be number 6. Not want i want to achieve.
 

(*steve*)

¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd
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Jan 21, 2010
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Sorry sniper123, xcoder is posting some rubbish and he's close to being banned.

Sorry I didn't pick it up earlier. I've removed his posts and the ones you patiently replied to him with.
 

(*steve*)

¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd
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Did you replace the diac?

It is possible that the triac has a higher trigger current requirement (and therefore does not trigger reliably at some "speeds").
 

sniper123

Oct 31, 2013
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Hi, all 5 components on the board have been replaced, inline with original schematic. The triac is 6 amp. I'm considering playing around with the values on the caps, especially the 47nF. See if anything alters there.

Its really like not enough power is getting thru' when it's running at minimum, whereas, when the speed is increased slightly, everything is fine.
 

(*steve*)

¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd
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Do you recall what the original slowest speed was? Is the mixer now trying to run slower than that when it does not run smoothly?
 

duke37

Jan 9, 2011
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A motor controlled by a diac/SCR pair is given a power thump when it is too slow. There is a minimum speed which gives a smooth control.

Some motors have strong cogging, they go round in jerks and need a certain speed to get them from one cog to the next. A series wound AC/DC motor is not likely to have strong cogging since there is no magnetism when there is no current.
 

sniper123

Oct 31, 2013
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Hi, no everything is the same. Which prompts me now to have a play with the centrifugal governor.

Cheers
 

sniper123

Oct 31, 2013
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So, still no joy.
The triac what is fitted is a BTA08-600B TO-220
Should I try an alternative triac, if so what????
 

duke37

Jan 9, 2011
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I would have thought that it is extremely unlikely that you have an intermittent electronics fault. Most semiconductors either work or dont. It could be a poor connection which is jiggled.

If the speed is controlled by a mechanical governor, then any friction in this will give poor control.
 

sniper123

Oct 31, 2013
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Hi, these mixers have a history of splutter as they get older, but my theory is, if somethings breaks it can be repaired. Nothing is loose, this is getting hard to solve.
The speed dial go from min 1 - 8, this is only happening at Min -1, as the speed is increased then the splutter goes.
 
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