Explain "Supercharging" an AC motor Please !

[Deadshort]

Roger that!!

On our vessels this is a common occurence.
We do not tap to ground so we have no Neutal on our system.
If one leg grounds on our 440, 220, or 110 volt systems then it will pull the other 2 legs of that system high. It doesnt need to be anything that big either for this to happen.

And should you happen to get 2 phases go to ground at the same time, it is not pretty.

With a factory full of 440 volt motors sitting just inches from the deck that has a continuous flow of salt water running across it, and a bunch of, Well, really special people doing high pressure, salt water washdown on everything including the electrical equipment, I end up looking for ground faults all the time.
(And NO they are not supposed to be washing the electrical equipment with HP salt water, but you can talk till you are blue in the face and it does little good)

We have ground fault meters on our main distribution board in the ECR that detect when voltage is going to ground.

BCS

Washing electrical equipment with high pressure salt water

You might as well stand on top of a hill in a lightning storm wearing wet copper armour and shouting "all the gods are bast@rds!" (with apologies to Terry Pratchett).

Sounds like the production employees in the wet pet food plant I am a maintenance electrician in. They routinely spray anything and everything with 400 PSI water, not salt water but it is treated with chlorine. We have local motor disconnects that fill with water on a routine basis so I ordered a drain to put in the box to keep it from filling. Our maintenance manager told me I couldn't use that I have to find the source of the water and fix it. I said OK I'll take all the hose reels out of the plant, actually I'll do one better, I'll shut off the wells, no more water issues.

The amount of stupid from management is unbelievable.

 

[milmat1]

OK Thank you for the great explaination, Now let me ask a more direct question related to this system
What happens when the V/HZ curve runs out of voltage? In other words we keep increasing frequency but we have hit the voltage ceiling. Of course we start to loose torque rapidly, But what happens to the current at this point ?

Heres the scenerio I have. A 3HP SEW Movidrive (61B) With a 2HP motor,(wired 230V) 40:1 gear reduction, We are moving a linear pusher.That moves brick onto a conveyor.
All my calculations show that at 2HP / 3600 RPM we have more than twice the force needed at full load. HOWEVER even at "0" Load the VFD is showing the motor being at FLA....Does this sound like a V/HZ problem ?

 

[Deadshort]

OK Thank you for the great explaination, Now let me ask a more direct question related to this system
What happens when the V/HZ curve runs out of voltage? In other words we keep increasing frequency but we have hit the voltage ceiling. Of course we start to loose torque rapidly, But what happens to the current at this point ?

Heres the scenerio I have. A 3HP SEW Movidrive (61B) With a 2HP motor,(wired 230V) 40:1 gear reduction, We are moving a linear pusher.That moves brick onto a conveyor.
All my calculations show that at 2HP / 3600 RPM we have more than twice the force needed at full load. HOWEVER even at "0" Load the VFD is showing the motor being at FLA....Does this sound like a V/HZ problem ?

Are all the drive parameters set correctly?

 

[Mill_Control]

OK Thank you for the great explaination, Now let me ask a more direct question related to this system
What happens when the V/HZ curve runs out of voltage? In other words we keep increasing frequency but we have hit the voltage ceiling. Of course we start to loose torque rapidly, But what happens to the current at this point ?

Heres the scenerio I have. A 3HP SEW Movidrive (61B) With a 2HP motor,(wired 230V) 40:1 gear reduction, We are moving a linear pusher.That moves brick onto a conveyor.
All my calculations show that at 2HP / 3600 RPM we have more than twice the force needed at full load. HOWEVER even at "0" Load the VFD is showing the motor being at FLA....Does this sound like a V/HZ problem ?

Are you using 230v or 460v FLA? Wiring the motor for 230v ~ doubles the current.

 

[DickDV]

A 2hp motor connected for 230V 60hz will have an FLA of around 7.2amps. At 460V 120hz, the FLA will still be 7.2amps.

Regarding your other question concerning field-weakened overspeed, the V/Hz ratio starts to fall due to the V being constant at its limit and the Hz continuing to increase.
The full load condition will still occur at full load amps.

Since the available output hp is constant in the normally-used field-weakened range, the input kw would have to hold constant as well. Since input voltage is constant and kw is constant, amps would be constant also.

 

[milmat1]

Are all the drive parameters set correctly?

Well that is my Argument with the manufacturer. I say there must be a problem with the V/HZ curve. and therefore th VFD is not properly setup. However that theory is met with much resistance..

 

[Mill_Control]

Well that is my Argument with the manufacturer. I say there must be a problem with the V/HZ curve. and therefore th VFD is not properly setup. However that theory is met with much resistance..

Post up the following drive parameters:

Motor Voltage

Motor FLA

Motor Base Frequency