Discussion Category: Centrifuge
Burns main 6 A fuse
I have this 5415 C centrifuge, I can spot nothing obvious. With the frequency dial at min it spins for several seconds and after that it burns the main 6 A fuse.
The rotor and stator coils are continuous. The relays look fine and I can see them closing and opening. The Hall sensor seems to work. The power on the fan is 15v and the speed sensor is 5v. Nothing appears burned.
The brushes are used but seem OK and the rotor is dirty but not badly pitted.
I don't have the schematics or the service manuals to be able to check more. If I take the motor power connector out the green light flashes and there is no power on the connector but the fuse does not blow.
If I put it back in and repower the device the green light is on and I can press the spin button.
The only things that appears suspicious is that the fan seems to be on all the time.
I'm kind of stuck and without some schematics I don't know what else I can do.
Thank you for any help,
Adrian
Reply byHi Adrian,
Are the bearings running smoothly on the main motor shaft?
Cheers, Jon
Reply byHi John and thank you for answering my post. The bearings seem to be OKish.
I did more tinkering and I realized that if I use the timer the centrifuge runs fine until I get the dial to about 5500 RPMs and after that I see the sparks on the brushed get more intense and the fuse blows.
Touching every board component after that finds them cool except for the right side (triristor?) component on the heat sink which is slightly warm.
When I run the centrifuge under 5500 RPMs it seems to go without prblems for minutes.
Cheers,
Adrian
Reply byHi Adrian,
Might be worth measureing the current draw on the motor if you have suitable measuring equipment.
Maybe the wear on the brushes is telling and at higher speeds, therefore load, the motor is pulling in access of 6A? That said i'd imagine the biggest current spike would be on initial motor start up.
Cheers, Jon
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