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Old March 13th, 2018, 09:56 AM   #1
ccopsey
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AB Power Flex 40 won't stop

I replaced a SMVector Lenze AC Tech drive with an AB PF40. From the keypad I can start it up just fine and it ramps up to the Hz requested. When I hit the stop button, it slows down to about 9 Hz and runs there until the drive faults out on an over current. It is extremely jerky when running at this approx 9 Hz.

I'm driving a router motor for an end effector of a Fanuc. The specs on the router motor are:
1.34HP
24,000RPM
400Hz
380V
3.2A

From the keypad, the only way I can get the router to stop is by pulling the factory installed jumper from the stop terminal. At that point it will coast until stopping.

The old drive had failed, and I am unable to get any of the settings from it. Any suggestions are helpful.

Chad
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Old March 13th, 2018, 10:38 AM   #2
Gene Bond
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It sounds like it's going into bus-regulation mode, meaning that it can't dissipate the energy in the bus capacitors which is coming from the motor/load. A shunt/DB resistor will help if this is the case.

Can you set the drive to coast to a stop? No faults?

From the jerky description at low speed, it sounds like the motor is over-excited, meaning either the v/f scaling is wrong, or there is too much low-speed voltage boost set.
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Old March 13th, 2018, 01:35 PM   #3
ccopsey
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The way I have it setup right now is with 2 wire control, and I have Terminal 1 and Terminal 2 jumped together. When I stop the drive through the controls, the Hz on the drive immediately drop to 0 and the router sloooooowly coasts down to stopped. I can run the system like this, but would like to ramp the stop down faster. I believe the book paramater list stated I couldn't ramp down the speed in a 2 wire control scheme.
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Old March 13th, 2018, 01:37 PM   #4
ccopsey
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How would I size a shunt / DB resistor and how would I discover if the v/f scaling is wrong?
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Old March 13th, 2018, 01:50 PM   #5
Geospark
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Quick pit stop...

29643 - PowerFlex 4 and 40 Minimum Dynamic Braking Resistance Values
Access Level: Everyone

If you need a quick calculation to determine whether you require a Dynamic Brake Resistor, or not...

594800 - PowerFlex drives: Requirement for Dynamic Brake Resistor
Access Level: Everyone

I'll let other drive experts handle the science part, I'm off home...

Regards,
George
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"A little nonsense now and then is relished by the wisest men".
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Old March 13th, 2018, 09:07 PM   #6
Cow
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Quote:
Originally Posted by ccopsey View Post
The way I have it setup right now is with 2 wire control, and I have Terminal 1 and Terminal 2 jumped together. When I stop the drive through the controls, the Hz on the drive immediately drop to 0 and the router sloooooowly coasts down to stopped. I can run the system like this, but would like to ramp the stop down faster. I believe the book paramater list stated I couldn't ramp down the speed in a 2 wire control scheme.
How long does it take to ramp it up to speed?

I believe it was Jraef on here that said you can never slow a motor faster than you can ramp it to speed.
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Old March 13th, 2018, 09:34 PM   #7
jraef
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If you have it set for Ramp to Stop (which is the default setting), it will attempt to do that, but if the motor regenerates back into the drive's DC bus, then you have "Bus Regulation" enabled (also the default setting) as Gene Bond said, the VFD will attempt to make the motor absorb the excess DC bus energy by continuing to motor it.

So you must do ONE of the following:
  1. Change the Stop setting to Coast, parameter P037 set to "1" or "5" (1 = Coast + CF for Clear fault", 5 = Coast only)
  2. Disable the Bus Regulation mode, parameter A117 set to "0", but with the Stop set to Ramp and no DB resistor, it will likely trip on Over Voltage
  3. Add a Dynamic Braking resistor connected to BR+ and BR-, along with numerous other settings in programming (read the manual yourself on that).
Pulling the jumper off of terminal 1 is emulating the setting of P037 to Coast by the way, so if that works for you, just change P037.
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Old March 16th, 2018, 10:41 AM   #8
ccopsey
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Thanks for the help. I opted to just let it coast to stop. I still occasionally get an F5 fault for an Over Voltage. Not exactly sure when it is happening. Could very well be when the router stops.
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Old March 16th, 2018, 05:01 PM   #9
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Quote:
Originally Posted by ccopsey View Post
Thanks for the help. I opted to just let it coast to stop. I still occasionally get an F5 fault for an Over Voltage. Not exactly sure when it is happening. Could very well be when the router stops.
While it is running or when stopping it?
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