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4kW Dahlander motor on Göckel G2 sharpener draws too much current evenly across all of the phases at slow speed (14 Amps instead of 8.5), keeps tripping. On high speed 5 Amps only. Resistance between all of the windings is 4-6 Ohm's. Must be evenly shorted windings somewhere, or previous owner might have been fiddling with the wiring somewhere.
 
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Andy-1960

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Check the wiring to the motor, in low speed voltage should be on U1, V1, W1 with nothing connected across U2,V2, W2.
In high speed U1,V1, W1 should be shorted out and voltage applied to U2,V2, W2.

If these connections have been reversed it will cause problems.
 
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Thank you for reply. Couldn't measure on the motor terminal box while the motor was moving (wasn't allowed to stop it cause the manager has too much work to do), inside the control panel everything measures as it should be- U1 V1 W1 shorted on high speed and ~230V across U1 V1 W1 on low speed.
Looks like the open frame motor has been standing in the rain for years so that might be the culprit.
 

Pete999

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How are the motor connections configured? is the motor stared DOL, Star Delta, slip ring resistance, soft start etc
 
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Well, it's a Dahlander motor with DOL starter. I'm quite reluctant when it comes to measuring the insulation resistance, especially on old motors, so will have to wait til it burns out. These non-standard frame motors tend to burn out quite frequently on sharpeners for some odd reason.
 

Andy-1960

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How are the motor connections configured? is the motor stared DOL, Star Delta, slip ring resistance, soft start etc
It's a bit weird Pete, there are basically two sets of windings, they are in series delta connectedfor one speed and in parallel star for the other.
 

Andy-1960

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Don't come across them much now since variable speed drives have become popular, but they used to be used a lot on extract fans in plating plants. As the metal went in... lots of fumes high speed extract, as it settled down and fumes reduced low speed extract
 
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There was a similar topic which sai
Thank you for reply. Couldn't measure on the motor terminal box while the motor was moving (wasn't allowed to stop it cause the manager has too much work to do), inside the control panel everything measures as it should be- U1 V1 W1 shorted on high speed and ~230V across U1 V1 W1 on low speed.
Looks like the open frame motor has been standing in the rain for years so that might be the culprit.
Actually might be other way around.

There was a similar topic on somewhere else which says that: ''The wiring could not be the cause, because in case of incorrect wiring the Amps would be much higher, even in both connections.
High NLA indicates a very bad design...''
Dahlander Motors - Electric motors & generators engineering - Eng-Tips - http://www.eng-tips.com/viewthread.cfm?qid=391897
 

Lucien Nunes

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How even is the low speed current distribution? A range of 4-6 ohms is quite wide, suggests to me there might be an inter-section short that has little voltage across it in star but is loading all phases by transformer action in delta. Can you clamp the individual winding sections instead of the outgoing leads? Currents should be very similar.
 
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How even is the low speed current distribution? A range of 4-6 ohms is quite wide, suggests to me there might be an inter-section short that has little voltage across it in star but is loading all phases by transformer action in delta. Can you clamp the individual winding sections instead of the outgoing leads? Currents should be very similar.
In the center of a double star connection there is around 1.8-2 Amps current flowing and around 4 Amps are going trough the outgoing leads in high speed mode. Probably will have to measure the inductance someday.
 
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