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#23163 - 03/12/03 06:04 PM VFD'S
sparky*62 Offline
Member
Registered: 07/27/02
Posts: 20
Loc: Ca.
I am having problems with a 2hp 460 volt vfd . It has blown the capacitors inside the drive. I megged the motor and wires and no faults there. It has happened twice. Any ideas?
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#23164 - 03/12/03 07:14 PM Re: VFD'S
WebSparky Offline
Member
Registered: 02/21/03
Posts: 138
Loc: Cleveland, Ohio
vfd=variable frequency drive?

If so, make sure the incoming voltage is within range and not too low, especially if the drive is reversing during it's normal run cycle.

Just a hunch......

Dave
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#23165 - 03/12/03 07:56 PM Re: VFD'S
bigrockk Offline
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Registered: 01/25/03
Posts: 174
Loc: Middle of Canada
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#23166 - 03/12/03 08:39 PM Re: VFD'S
Bjarney Offline
Moderator
Registered: 04/10/02
Posts: 2527
Loc: West-Southern Inner-Northeast ...
High temperature and overvoltage can be tough on electrolytic capacitors. Check line-side diodes to be sure one didn't fail, injecting AC into the DC bus/capacitor(s). Sometimes smaller VFDs become such a narrow-profit commodity that it’s cheaper to do a wholesale replacement. Some make good boat anchors—many do not.
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#23167 - 03/12/03 09:42 PM Re: VFD'S
Trumpy Offline


Member
Registered: 07/05/02
Posts: 8211
Loc: SI,New Zealand
62,
What sort of cabling are you using between the drive and the motor?.
Is there any Mains-borne interference on the wires feeding the VFD, these units need a perfect Sine Wave input or there will be problems.
Unfortunately, you will need an oscilloscope,
to see what the waveshape is like, any harmonic interference on the lineside of the VFD, cause wierd currents to flow where they shouldn't.
Hope this helps.
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#23168 - 03/13/03 02:50 AM Re: VFD'S
zapped208 Offline
Member
Registered: 02/18/03
Posts: 196
Loc: Somewhere in USA
62,- This could be almost anything, like maybe a scr, rectifier, diode, or trim pot. Did you take it apart to see any possible over heating on the boards? Might be a good idea to call the drive's tech dept. for some help. did you disconnect motor leads from the drive before you meggered??
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#23169 - 03/13/03 04:02 AM Re: VFD'S
gramps Offline
Member
Registered: 08/25/02
Posts: 112
Loc: ohio
check the output at the d.c. bus. should be between 700 and 800 VDC, for a 460 volt drive. if its not in this range, you prolly have an SCR problem.


gramps
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#23170 - 03/13/03 08:01 AM Re: VFD'S
Pearlfish Offline
Member
Registered: 09/12/02
Posts: 83
Loc: Chicago Ridge, Il, USA
How much torque is on your load and what is your Decel time? If your decel time is too short you will have too much regenerative current feeding back into your drive. A properly sized braking resister might help.
JMHO
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#23171 - 03/13/03 02:21 PM Re: VFD'S
Format_C: Offline
Member
Registered: 08/14/02
Posts: 29
Loc: Bridgeport, Connecticut, USA
What are VFDS? I thought it meant Vacuum Flourscent Display (VFD) Like the displays in VCRs, DVDs, Receivers etc. Those displays are also used in computers now.
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#23172 - 03/13/03 02:27 PM Re: VFD'S
iwire Offline
Moderator
Registered: 01/05/03
Posts: 4391
Loc: North Attleboro, MA USA
Variable Frequency Drives

They control frequency and voltage supplied to standard AC motors so you can ramp them from 0 RPM to above the nameplate RPM if the motor can take it.
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Bob Badger
Construction & Maintenance Electrician
Massachusetts
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