power flex 400

[mavrick]

I have a drive that keeps faulting when I turn off my pump. At first it was giving me a hw overcurrent so I increased the accel time and it seemed to remedy that problem. Now I keep getting a over voltage or over current fault when I shut the pump off. I have increased the decal time per the manual and still have had no luck remedying the issue. Also if I shut the disconnect off between the pump and drive then rest the fault the pump will restart. If I do not shut the disconnect off the fault will keep happening every time I reset the drive and then try to start it. This is a power flex 400 drive and it is feeding a 30hp motor that is turning a pump. Any help on fixing this issue would be appreciated. Thank you

 

[jraef]

As always, the first question is;
Was it working fine and just started to do this, or is this a new installation and you are just starting out? Makes a big difference.

 

[widelto]

I have a drive that keeps faulting when I turn off my pump. Also if I shut the disconnect off between the pump and drive then rest the fault the pump will restart. If I do not shut the disconnect off the fault will keep happening every time I reset the drive and then try to start it. This is a power flex 400 drive and it is feeding a 30hp motor that is turning a pump. Any help on fixing this issue would be appreciated. Thank you

Mavrik: what specifically have you connected between drive and pump.

 

[mavrick]

yes , this system was in operation for a couple months with no trouble and then it started acting up. As far as what is between the drive and the motor. There is just a basic 30 amp non-fused disconnect between the two.

 

[jraef]

Most likely you are getting an OV fault because when you shut the drive down, and it is det to Decelerate the motor (likely to avoid water hammer), the flow is going backward and over driving your pump motor, which is putting it into regen and charging up the DC bus. If you had a check valve, it's probably stuck open.

 

[jdbrandt]

Most likely you are getting an OV fault because when you shut the drive down, and it is det to Decelerate the motor (likely to avoid water hammer), the flow is going backward and over driving your pump motor, which is putting it into regen and charging up the DC bus. If you had a check valve, it's probably stuck open.

+1 on the regen comment.

The energy is coming from somewhere.......

 

[Cow]

Most likely you are getting an OV fault because when you shut the drive down, and it is det to Decelerate the motor (likely to avoid water hammer), the flow is going backward and over driving your pump motor, which is putting it into regen and charging up the DC bus. If you had a check valve, it's probably stuck open.

Could he simply set the stop mode to coast? Even if he's using the PID function, that shouldn't affect the ramp rates should it?

 

[rootboy]

Could he simply set the stop mode to coast? Even if he's using the PID function, that shouldn't affect the ramp rates should it?

That's what I would do. It's a good place to start troubleshooting at least.

 

[GaryS]

I agree change to coast to stop, but in addition add a mandatory restart delay long enough to be sure the pump is completely stopped before the restart.
Restarting the VFD with the connected motor running either forward or reverse would cause an overload and could burnout the VFD. One absolute rule, never ever connect a motor to a running VFD.
It would appear that the VFD internal braking resister did work for a while then failed at a later time. That would be in line with the description. The internal braking transistor and resistor are usually rated at about 10% duty cycle. It would brake the motor for a while and then open up.

 

[Tom Jenkins]

Is there a check valve on te pump discharge, and is it working?

 

[mavrick]

there is a check valve and it appears to be working correctly. When the pump is shut off I do not see ant reverse flow of material turning the pump shaft. I would like to add that I am pumping a cooked mash for distilling so this is not just a thin liquid. also how can I tell if this drive is equipped with an Ethernet card where I could connect either net to it? It is currently being controlled with a 2 wire system. Is adding the restart delay listed in the basic programming section.

 

[jraef]

Sometimes on a high viscosity fluid, I've seen where the fluid cannot change flow as fast as the drive tries to change it, the mass of it just keeps going and pulling more through as you try to decelerate the drive. Why it would just start doing that now would be a puzzlement though.

Over voltage on the DC bus can also be caused by resonance with external capacitors too. Was anything new added to your facility recently? Some large load with Power Factor Correction Caps would be a prime suspect.

As suggested, set it to Coast to Stop and if the problem persists, it's not load related. If that stops it from occuring, it was.

 

[Phil Buchanan]

Over voltage on the DC bus can also be caused by resonance with external capacitors too. Was anything new added to your facility recently? Some large load with Power Factor Correction Caps would be a prime suspect.

Or were any major loads moved or removed that would cause a voltage increase in that area? If you line voltage is going to high it can cause DC bus over voltage issues also. This can be solved with a line reactor of the correct percentage.