crane motor fusing

catalin78

Member
Join Date
Feb 2005
Location
Constanta
Posts
115
i have the following problem on a crane:
the fast action fuses wich are installed on output of the dc drive (simoreg) burn sometimes during the driving of dc motor for rotating arm .

conection is mains > fuses > inverter > fast action fuses > motor

some hints about what could happen? . motor is about 200 kw
or less . note that the first fuses dont burn out only the fast acting ones on output of the drive.
 
Fast acting HRC fuses are there to protect the electronics. Slower acting fuses are usually far too slow to protect the electronics.

I would suggest you find out what is causing the fuses to blow.
 
But from what I understand, the fast acting fuses are between the drive and the motor so the only thing it would be protecting is the motor.
 
No. They are protecting the drive from short circuits in the motor that may damage the SCR outputs.
 
Unless this is a very old analog DC drive, that current limit should be in the drive software, not in motor lead fuses.

I would check the drive instruction manual. It may be that those fuses don't belong there at all.
 
It might be a good idea to check for intermittent field loss. If you loose the field current, the armature will draw excessive current.
 
field current?

Thanks all for your help . I would ask kindly that Logix explains in more detail what field current loss is and how can it affect armature current , the dc drive is simoreg dc 210 amps in four quadrant .
 
Is this a new installation or an old one ? My experience with DC motors (albeit with smaller motors) is that the brushes/commutator wear and carbon dust builds up providing a short circuit path which then blows the drive output fuses. If the drives uses SCR's, then once they have started conducting they will not stop until the volts have gone to zero, hence the (usual) need for output fuses.
 
Simon , the motors have a current of 100 A the control is made with simoreg from siemens the installation is 3 years old , the problem is within 1 year . Last year the scr`s in the drive were short circuited , (two of them) we don't know the reason we suspected the regenerative power corection module and resistors ...
Any info may help
 

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