Powerflex 4m

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jomamma1

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Modesto, California, USA
Background: I am replacing an obsolete Allen Bradley 160 VFD with a PowerFlex 4M. Older 160 used a dynamic braking resistor. When we powered up the PFlex, the dynamic braking resistor burned immediately. I have ordered a new resistor for the new drive, but before I power it up again I want to make sure that all setting are correct. Have any of you had this problem? Any advice?
Thanks,
Joe in Modesto
 
petersonra

petersonra

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Northern illinois
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engineer
Odd that it would energize the resistor at all on power up as there can't be excess voltage on the DC bus.

I would be inclined to reset the drive to its default parameters and then set whatever parameters need setting.
 
Jraef

Jraef

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ptonsparky said:
Looking at the terminal locations on the VFD, it would appear to be an OS moment by the installer. The OS moments, I have experience with. Braking resistors, I do not.
Click to expand...

After I got my BS degree, I entered the workforce and got my OS degree...

I'll bet I know exactly what the OS moment was on this one. The PF4M in the sizes below 7-1/2HP at either voltage do not have internal Dynamic Braking transistors. If you connected the resistor to DC+ and DC-, you connected directly to the DC bus in the drive. Hopefully you didn't damage the drive. Probably not though, the resistor would have acted like a current limiter until it became a fuse, and hopefully the current limitation was below the damage curve of the diode bridge.

If you need the braking, you need to change to the PF523. It has a mounting accessory that adapts the 523 for feed through wiring like the 160 had. Then double check your resistor values befor using it.
 
petersonra

petersonra

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Location
Northern illinois
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engineer
Jraef said:
I'll bet I know exactly what the OS moment was on this one. The PF4M in the sizes below 7-1/2HP at either voltage do not have internal Dynamic Braking transistors. If you connected the resistor to DC+ and DC-, you connected directly to the DC bus in the drive. Hopefully you didn't damage the drive. Probably not though, the resistor would have acted like a current limiter until it became a fuse, and hopefully the current limitation was below the damage curve of the diode bridge.
Click to expand...

That would do it. I never even considered someone would do that.
 
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mike_kilroy

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United States
Where in the heck is our LIKE button???

Where in the heck is our LIKE button???

ptonsparky said:
Looking at the terminal locations on the VFD, it would appear to be an OS moment by the installer. The OS moments, I have experience with. Braking resistors, I do not.
Click to expand...

Not only the likely reason, but so eloquently stated!!

Thank you for making my day!
 
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