Danfoss autopsy

[J.E.B.]

Recently I dissected a danfoss variable speed a.c. moter drive. I
found what looked like two transformers with only to wires coming from
each. Are these transformers? If so how would this work? anybody
familar with danfoss drives?

 

[John Popelish]

Recently I dissected a danfoss variable speed a.c. moter drive. I
found what looked like two transformers with only to wires coming from
each. Are these transformers? If so how would this work? anybody
familar with danfoss drives?

They sound like inductors. I'll bet that the cores consist
of a stack of Es and a stack of Is separated by a thin
spacer, rather than interleaved Es and Is the way
transformers are made.

 

[J.E.B.]

They sound like inductors. I'll bet that the cores consist
of a stack of Es and a stack of Is separated by a thin
spacer, rather than interleaved Es and Is the way
transformers are made.

Thanks for the reply John. Pardon my ignorance, But what purpose would
these serve? P.S. This is a VLT 5000 series BTW.

 

[John Popelish]

Thanks for the reply John. Pardon my ignorance, But what purpose would
these serve? P.S. This is a VLT 5000 series BTW.

I can only guess, but inductance limits the rate of rise of
current when a voltage is switched on. This effect can be
used as a way to figure out that the motor leads are shorted
and switch back off before the short produces damaging
current levels, or as high frequency noise filter
components. If being used in the motor circuit, I would
have expected 3 of them. With only two, they are more
likely part of the supply noise filter. Is this drive
powered by single phase or 3 phase?

 

[J.E.B.]

I can only guess, but inductance limits the rate of rise of
current when a voltage is switched on. This effect can be
used as a way to figure out that the motor leads are shorted
and switch back off before the short produces damaging
current levels, or as high frequency noise filter
components. If being used in the motor circuit, I would
have expected 3 of them. With only two, they are more
likely part of the supply noise filter. Is this drive
powered by single phase or 3 phase?

3 phase. 460 delta.

 

[Homer J Simpson]

Recently I dissected a danfoss variable speed a.c. moter drive. I
found what looked like two transformers with only to wires coming from
each. Are these transformers? If so how would this work? anybody
familar with danfoss drives?

Either they are chokes or there is also one large wire going through each.

 

[J.E.B.]

Either they are chokes or there is also one large wire going through each.

These are wound with what appears to be 16 to 14 gauge.

 

[John Popelish]

3 phase. 460 delta.

Do you have a model number?

Does it look like any of these?
http://www.namc.danfoss.com/products/drives/index.html

 

[J.E.B.]

Do you have a model number?

Does it look like any of these?http://www.namc.danfoss.com/products/drives/index.html- Hide quoted text -

- Show quoted text -

Yes its the vlt 5000 series.

 

[John Popelish]

Yes its the vlt 5000 series.

Unfortunately, this data sheet does not have a schematic,
but includes lots of info about the general concept of the
drive:
http://www.namc.danfoss.com/literature/drive_eng.pdf

 

[John Popelish]

Unfortunately, this data sheet does not have a schematic, but includes
lots of info about the general concept of the drive:
http://www.namc.danfoss.com/literature/drive_eng.pdf

Can you trace if these two inductors are part of the DC
filter between the 3 phase rectifier and the storage capacitors?

 

[Homer J Simpson]

These are wound with what appears to be 16 to 14 gauge.

Pretty much chokes then.

 

[Homer J Simpson]

4. Intermediate circuit coils

Smooths the intermediate circuit current and limits the load on AC line and
components (AC line transformer, wires, fuses and contactors).

 

[jntel]

Recently I dissected a danfoss variable speed a.c. moter drive. I
found what looked like two transformers with only to wires coming from
each. Are these transformers? If so how would this work? anybody
familar with danfoss drives?

They are DC line reactors. There is one placed in the (-) and one placed in
the (+) leg between the 3 phase input full wave bridge rectifier and the
capacitor bank. They are used for harmonic control. External input line
reactors are not needed.

Jeff