VFD

[ASK_EDDIE]

I am suppose to provide power to an Allen Bradley Powerflex 70 feeding a 15hp

They are suppose to provide the AB and the motor, Ive never worked with a VFD so please excuse these basic questions. From searching the internet, it seems the OL protection is provided by the VFD itself.?
Since these are being provided to the company as a package deal are these programed ? do they normally need set up programing ?I will not be providing any of this Im just wondering.
Can any basic AC motor be used with a VFD or are they a special type of motor.
As you can see I have no business working on a VFD and i wont be , I Just think should know some basics to even provide the circuit to their cabinet.
If you can think other basic points i would appreciate it.

 

[Besoeker]

I am suppose to provide power to an Allen Bradley Powerflex 70 feeding a 15hp

They are suppose to provide the AB and the motor, Ive never worked with a VFD so please excuse these basic questions. From searching the internet, it seems the OL protection is provided by the VFD itself.?
Since these are being provided to the company as a package deal are these programed ? do they normally need set up programing ?I will not be providing any of this Im just wondering.
Can any basic AC motor be used with a VFD or are they a special type of motor.
As you can see I have no business working on a VFD and i wont be , I Just think should know some basics to even provide the circuit to their cabinet.
If you can think other basic points i would appreciate it.

Most VFDs I've come across already have default parameters that will do for basic applications. If you want the drive anything beyond the basic like for example accept start, stop and speed commands from elsewhere you would most likely have to set parameters to do that.

Usually, the motor has to be rated for VFD operation. The output of the VFD is a series of pulses with very fast rising edges and the windings of just any old motor tend not to like that. It can lead to insulation failure sometimes in a relatively short period. It can be resolved by using filters between the VFD output and the motor.

Even if the motor is designed for VFD operation, you still may need output filters if the motor is over a certain distance from the drive. And you may need special cable. I'm from UK and it isn't often a problem here as we mostly use steel wire armoured cable for all power cabling including motors. We hardly ever use conduit but if you do, don't put signal cables in with the motor cables.

Depending on the type of load and speed range, the motor might need additional external cooling - the normal shaft driven fan isn't very effective at lower speeds.

You also need to make sure the VFD can get good ventilation - don't stick it in a broom closet....

 

[sgunsel]

Yes the VFD will provide OL protection, as well as phase loss, undervoltage and overvoltage protection and soft starting/stopping. But the VFD needs to be programmed for the application. Maybe the supplier is doing this, maybe not.

Start/stop times, maximum and minimum rpm, auto restart or not on power loss/resumption, type of controls, and reverse lockout are typical parameters that should be addressed. There are many other parameters that can be changed, so check the VFD manual to see if any of those are appropriate for the application.

I believe that modern VFDs can be used on any three phase motor, as long as the voltage and available current are correct. I have seen many older motors retrofitted with VFDs without ill effect, but since these are being provided as a package, that shouldn't be a concern.

Make sure you read the manual instructions for installing for proper sizing of wiring and overcurrent protection. Also, you do not want to open the circuit between the VFD and the motor while running. If a disconnect must be placed there, a warning label should be affixed to the disconnect warning against opening whie the motor is in operation, except in an emergency.

 

[don_resqcapt19]

I am suppose to provide power to an Allen Bradley Powerflex 70 feeding a 15hp

...

You will need to know the rated input current of the VFD. The feed to the drive is required to be sized at 125% of the drives rated input current. 430.122

 

[Besoeker]

I believe that modern VFDs can be used on any three phase motor, as long as the voltage and available current are correct. I have seen many older motors retrofitted with VFDs without ill effect,

I have seen a fair few that have not been OK. And not just older motors. On one particular project there were four new 750kW motors and VFDs - we made the VSDs but not the motors.
The motors started failing after just a few weeks of operation. Nobody was happy. As one wag from the main contractors put it "750kW motors should not be considered consumables."

All four motors were rewound with better insulation. As it happens, we did have output chokes and the dv/dt applied to the motor windings wasn't all that high. It's just that the motor manufacturer hadn't appreciated the need to rate the motor insulation correctly for the application.

 

[Jraef]

Maybe the supplier is doing this, maybe not.

I think this brings up a very important point. Make sure BEFORE YOU GO that everyone understands the extend of your responsibility. End users LOVE to jump on grey areas and start withholding payment when something is incomplete, which can leave you waiting to get paid as everyone argues about what is considered part of "normal" installation. Been there, done that, got the t-shirt and the hat.

Also as previously said, make sure you understand the subtlety of that 430.122 reference, you must size the circuit for 125% of the VFD's FLC, not the motor FLC, which will be less. So before you buy your components, make them give you the EXACT number from the unit being supplied. A big pitfall for installers is that someone ASS-U-Me s the size of the VFD and it turns out that some salesman gave them a deal on a larger unit, or the larger unit is all they could ship on time, etc. etc.. Then YOU, the installer, get stuck with cut wire that is too small, restock charges for breakers etc and another trip to the job site you hadn't planned on.

 

[ptonsparky]

We recently installed a Softstart as a complete package supplied from someone else. No parameters were set. Another setup had all the parameters set, just the fusing was not good.

 

[mbeatty]

Most VFDs I've come across already have default parameters that will do for basic applications. If you want the drive anything beyond the basic like for example accept start, stop and speed commands from elsewhere you would most likely have to set parameters to do that.

Usually, the motor has to be rated for VFD operation. The output of the VFD is a series of pulses with very fast rising edges and the windings of just any old motor tend not to like that. It can lead to insulation failure sometimes in a relatively short period. It can be resolved by using filters between the VFD output and the motor.

Even if the motor is designed for VFD operation, you still may need output filters if the motor is over a certain distance from the drive. And you may need special cable. I'm from UK and it isn't often a problem here as we mostly use steel wire armoured cable for all power cabling including motors. We hardly ever use conduit but if you do, don't put signal cables in with the motor cables.

Depending on the type of load and speed range, the motor might need additional external cooling - the normal shaft driven fan isn't very effective at lower speeds.

You also need to make sure the VFD can get good ventilation - don't stick it in a broom closet....

Great advice.