fcc
Joined: 01 Jun 2003
Posts: 1
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 01 Jun 2003 4:02 Teco/Westinhouse GA7200 VFD problem |
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Hi folks, my shop neighbor has two of these as motor controllers for his Acra Milling machines. I got to program them because I installed one on my bandsaw so I'm the "expert" 
So we have a problem, these are set up with the frequency max set at 120 HZ. I have involked a decceleration ramp by SN04 set to 0000, BN02 set to 4 sec and injection breaking set (CN10-12, --- I have these memorized, eek!) to 10 percent freq cut on at 75% torque for 1 sec. These settings work just fine on my inverter running at 60hz max but on his machines if we trigger stop at over 75hz the machine ignores braking and just coasts to a stop. No error codes and the voltage across the braking resister terminals remains at zero (no resistor installed).
Westinghouse has given me a big shrug of the shoulders, anyone know anything about these?
fcc
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hobbymat
Joined: 16 Feb 2003
Posts: 35
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| 21 Jul 2003 17:14 |
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If the motor connected to the VFD (inverter) is considered too big for normal braking (by the inverter), it may need a braking resistor or an active braking module. I mean that if the internal braking currents get too high the drive may automatically just let the motor to coast to stop in order to avoid burning its transistors.
If you want to connect a braking resistor, be absolutely sure that you can connect just a passive resistor without any active transistor things that control the braking current. Usually the manual will tell which kind of braking accessory this particular drive model uses. Typically there are only two terminals for this, so it's easy to accidentally connect a resistor in the case that you should use an active module. At least this applies to many ABB and SquareD (Telemecanique) drives.
Hope this helps even a bit.
Hobbie
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