Powerflex 40 3 min reset?

[baduc11]

is there anyway to discharge the capacitor without waiting the 3 mins to reset the drive?

 

[jraef]

is there anyway to discharge the capacitor without waiting the 3 mins to reset the drive?

Safely? No, and this is true of virtually all AC VSI drives. You have bus caps, they store energy, that energy has to dissipate, that takes time if you want low risk of damage.

 

[DickDV]

I guess I'm a bit confused over this question. Resetting from a fault has never had a time delay, to my knowledge. Is this a power-down situation? How would you control how fast the power comes back in a thunderstorm, for example?

Maybe this is a comm reset but then the bus caps aren't involved.

Somebody help me out with this!

 

[osmanmom]

complicated to answer

 

[baduc11]

I suppose I worded my question incorrectly, is there a way not to wait the full 3 mins for the drive to completely shutdown. sorry for the confusion. I've talked to my local Rockwell tech and his only solution is to change the drive to 525 to use safe off, I am not completely against this other than the simple fact that we have just recently in last couple years evolved over to the 40's set. If there isn't a safe way to do it then I rather not take the chance, just thought someone might know of a way. thanks.

 

[jraef]

I suppose I worded my question incorrectly, is there a way not to wait the full 3 mins for the drive to completely shutdown. sorry for the confusion. I've talked to my local Rockwell tech and his only solution is to change the drive to 525 to use safe off, I am not completely against this other than the simple fact that we have just recently in last couple years evolved over to the 40's set. If there isn't a safe way to do it then I rather not take the chance, just thought someone might know of a way. thanks.

Now I am confused too. The fact that the 525 has "Safe Torque Off" changes nothing about the fact that the DC bus is still charged. So is the issue behind all this that someone has a fear that if there is a safety shutdown, it takes the VFD 3 minutes for the display to go blank, and someone is concerned that this could somehow result in an inadvertent movement of the motor? Because if it is a "Safety category" issue now with the PF40s, the only way you can attain that is by having an output contactor (or two, depending on the level), in which case the DC bus being live becomes irrelevant. In other words if someone is thinking that just because the display is dead and that USUALLY means the DC bus is discharged and therefor "safe", will not, as far as I know, be qualified for any SIL / pl level.

 

[OkiePC]

I think what he is talking about is powering down the drives, and having to wait for the full discharge of the bus before restoring power.

If you cut the time really short, you risk drive damage and nuisance faults since the DC Bus low faults will not have been cleared by a proper power up sequence.

3 minutes is probably some rule of thumb. Put your cat 3 meter on DC and measure the DC bus. When it drops below 20 or so, you are good to go to work on it. You will find some drives power down quite quickly depending on what they are doing and how they are programmed.

If you cut the time a little bit short, you may risk some drive damage, but those are disposable drives anyway, don't use the built in power supply if you can help it, and keep a spare or two handy.

I have used the safe off option with the PF70 series so you might step up to that model if your application suits it (safe off) and it accomplishes your desire (uptime) with a reasonable payback.

My understanding of Safe-Off, is that it is a monitored force guided relay hardwired into the IGBT gate signals or something to the effect, and can be part of a category 3 system.

When I have it my way, for MCR and e-stops, I like to keep the drives powered and use contactors between the VFD and the motors. wire the enable (coast input) through an auxiliary contact, and let the safety circuit open those many contactors instead of power cycling all those expensive drives. Many people will say that this is bad for the drive, but as long as you shut it down first or simultaneously and close the contacts (reset the safety circuit) before commanding it to run again, the drive will be just fine and happy not having to faint out and be reawakened every time an operator needs to tweak an adjustment inside a door.