Inverter question

[leitmotif]

IF it runs well on supply of 400 V 3 phase with motor connected in star
why not be happy and leave it alone?

Why mess with single phase and changing connections?
ALSO
on single phase the recifiers are the limiting factor and that may require derating the drive.

Dan Bentler

 

[flowdam]

Thanks for the info DickDV. I know who to call the next time I have a drive problem.

 

[meister]

The reason why we want to run with the 1-phase inverter is because we want to have the possebility to install the lift in places were 3-phase is not available.

DickDV, about increasing the tourqe limit,,
Actualy the inverter is oversized for the motor. So we have a 2,2kw inverter and a 1,1kW motor. When we run the motor on the 230V inverter the motor runs fine up to 50Hz, after this the current starts to rise and when we get closer to 60Hz, current starts to rise very rapidly and motor starts to stall and then stop, at this point the current is very high for the motor but the inverter has more current to give. We never get any alarm from the inverter!

Kalle, your point about field weakening area is very interesting. I am going to look into this further.

Maybe it is a combination of different cases;
1 Motor has a little bit less tpourqe at rated speed Star connection
and not sized with any margin (DamianIn)
2 Inverter comes into field weakening area with the 200V inverter above 50Hz

For info: inverter has at the moment only been tested in V/F mode.
We will try to do some testing in open loop vector and see if there is a difference.

If any one has more info about the phenomena that the tourque charasteristics are differént in star/delta connection I am happy to listen.

 

[KalleOlsen]

If you can find the same motor winded for 230/130 V, and the VFD allows it, you could keep the Delta coupling in the motor and still have 'spare' voltage to run overrated freq.

If you want, I can see if I can find an example from Siemens (or was it Bauer/Danfoss?). It was about 400V VFD and 230V coupled motor running up to 87Hz.

Kalle

Edit: Here it is http://support.automation.siemens.com/WW/view/en/41315157

 

[meister]

Kalle, This is not an option because we want to use the same motor all the time but different inverters depending on the voltage supply on site.

But I understand what you mean,,,
Connecting a 230/130V motor to a 230V inverter Delta connection and getting the base frequency at 87Hz with x1,73 higher current.

 

[flowdam]

current starts to rise very rapidly and motor starts to stall and then stop, at this point the current is very high for the motor but the inverter has more current to give. We never get any alarm from the inverter!

By this statement, I would also tend to think that there is a difference in the torque characteristics of the motor between running in delta and wye, but that would be something you should be able to confirm with the manufacturer.

If this is the case, you may be able to either change your gear ratio if not direct drive or up the KW on the motor if it is.

One other thing that I'm sure you checked, but could still be worth mentioning- has the motor been properly reconnected for delta? The motor would most likely still run when connected wye, but would be very weak.

 

[meister]

Hello Guys!

So we have found the problem!
When we were running the inverter with 1-phase, the supply voltage actualy droped because the grid could not supply sufficient power.
But the inverters capacity is up to 20,6A or 30,9A in 1 minute.

So there were no problems with inverter or the motor.

We could solve this issue by using the function Stall prevention. What happens then is that the inverter goes down in speed when it reaches maximum current, if the grid can not supply enough power. Another solution would be to have the inverter running in open loop vector control and use the Tourqe limit function.
But these solution would mean that if the grid can not supply sufficient power the inverter would go down in speed to compensate.

Anyway the problem is the grid so there we have to get the power company to fix it.

Thanks every one for your inputs.

Br

 

[flowdam]

Interesting meister. I would never have thought supplying 2KW would cripple a power company.

Anyway, glad you found it and come hang out any time.

 

[Lancie1]

Interesting meister. I would never have thought supplying 2KW would cripple a power company.

It probably didn't actually cripple the power company. Most likely, the 3-phase transformer could not supply the unbalanced load to the single-phase drive running on a 3-phase circuit. It just did not have enough reserve capacity for that much unbalanced load, so the voltage dropped off (on one phase) enough to cause the current to bump against the drive Current Limit setting.

 

[DamianInRochester]

It probably didn't actually cripple the power company. Most likely, the 3-phase transformer could not supply the unbalanced load to the single-phase drive running on a 3-phase circuit. It just did not have enough reserve capacity for that much unbalanced load, so the voltage dropped off (on one phase) enough to cause the current to bump against the drive Current Limit setting.

To Lancie's point, might be worth trying to run off of one of the other phases. Maybe you just got unlucky and picked the phase that is already the most overloaded.

 

[flowdam]

meister- check you private message box when you get a chance.