VFD in a DOL Motor

one more thing that came to my mind..

The motor plate says 380V 50Hz so in the parameters of the VFD, I put 380V in the motor voltage and 50Hz in motor freq.

However the supply line is 400V and 50Hz..

That might be the issue then ?? because the VFD when supplying 50Hz output voltage will be 380 instead of 400 right ??
 
HZ dictates rpm, voltage will dictate amps. The load will demand an amount of power, the vfd will provide this via voltage and hz manipulation up to the limits programmed for volts, amps, Hz.

The supply line is irrelevant to the motor side of the VFD. The drive will convert the incoming AC to a DC bus, then uses pulse width modulation (or some other trickery, but usually PWM) to "simulate" an AC power to the motor. The input does not affect the output directly, except maybe if insufficient power.
 
Robb B said:
HZ dictates rpm, voltage will dictate amps. The load will demand an amount of power, the vfd will provide this via voltage and hz manipulation up to the limits programmed for volts, amps, Hz.

The supply line is irrelevant to the motor side of the VFD. The drive will convert the incoming AC to a DC bus, then uses pulse width modulation (or some other trickery, but usually PWM) to "simulate" an AC power to the motor. The input does not affect the output directly, except maybe if insufficient power.
Click to expand...

Ok,,, but in order to be the same using VFD or DOL, the supplied voltage and Hz should be the same..

How does the VFD knows that for 50Hz it should supply 400V and not 380V ?
 
The VFD knows nothing except what you program it. It is entirely possible to supply a VFD with 480V AC so it can run a 380V motor. You could also supply it with 240V single phase, and put out 600V 3 phase (assuming correctly rated VFD is used, and serious derating is applied, good topics to search and read on this site). Wondrous things, VFDs....
 
Robb B said:
The VFD knows nothing except what you program it. It is entirely possible to supply a VFD with 480V AC so it can run a 380V motor. You could also supply it with 240V single phase, and put out 600V 3 phase (assuming correctly rated VFD is used, and serious derating is applied, good topics to search and read on this site). Wondrous things, VFDs....
Click to expand...

Hi Robb !

Yep, you are right.. what i tried to say is that in the configuration of the VFD. When you enter the parameters of the motor, if you put that in the Nominal voltage of the motor is 380V and nominal freq is 50Hz, I assume that when you start the motor and put the speed reference to 50Hz, the output voltage would be 380V right ? even though the supply voltage to the VFD is 400V.

What im trying to say is that, without the VFD the supply voltage to the motor is 400V and 50Hz freq. with the VDF installed, and the motor parameters as i wrote before, if the speed ref is 50Hz the supply voltage (output of VFD) will be 380V insted of 400V and thats why is rotating at a different speed ??

Thanks!!
 
50Hz will be full nominal nameplate speed, whether it comes from a VFD or a standard motor starter (across the line).

https://en.wikipedia.org/wiki/AC_motor#Induction_motor

Yes, the output voltage will be whatever you entered for parameters. The speed is irrelevant of the voltage. Voltage provides the potential to do work, the speed will be determined by the Hz (and the number of poles of the motor, slip if any, basically any of the physical design characteristics). This is all for very standard VFD rated squirrel-cage type motors, other designs of motor function differently.
 
Have you accounted for losses during start and stop due to acceleration and deceleration in VFD vs DOL
 
rupej said:
If the VFD is configured for V/F, then it is not using slip compensation, so this doesn't apply. Some VFDs are configured for sensorless vector and use slip compensation by default, though. So you wouldn't need to ever think to set it.

What is the brand/model of VFD you are using?
Click to expand...

Slip compensation existed long before SVC came along. It is not necessary to have SCV in order to implement Slip Compensation, it's just more accurate.

But I agree, that is likely what is taking place here.
 
On most VFDs, if you tell the drive the motor is rated for the synchronous RPM (1800, 1500, etc.) then the slip compensation does not come into play. You would have the same RPM as if the motor was DOL...

There are also (typically) some slip-comp parameters that can be adjusted up or down.
 
Hi, just for everyone who followed this thread,

I could fix the issue, somehow it came configured by factory for 60Hz despite all the parameters I introduced were for 50Hz, and it seemed everything was for 50hz there must have been some parameter that was messing around.

I factory reset the VFD and set it for factory 50Hz, introduced all the parameters of the motor again and it worked perfect.
 
joaco1993 said:
Hi, just for everyone who followed this thread,

I could fix the issue, somehow it came configured by factory for 60Hz despite all the parameters I introduced were for 50Hz, and it seemed everything was for 50hz there must have been some parameter that was messing around.

I factory reset the VFD and set it for factory 50Hz, introduced all the parameters of the motor again and it worked perfect.
Click to expand...

Thanks for letting us know!
 
joaco1993
What part of New York are you in in your origenal post you stated the motor was running at 50Hz witch was the supply
All of the US is in on motor would or pare of the grid the grid in 60Hz so a 50Hz motor would be running faster it it is on 60Hz
VFD's shipped in the US for use in the US are default set would be 60Hz
you could run a 50Hz motor at 60Hz without any problems it would just run faster
if it to be on 50Hz system it would have to be on a private system and never ever connected to the grid
for reference their is a 25Hz system in the north east US (Amtrack / Conrail ) and only used for trains.
so you origenal post is a little confusing
 
GaryS said:
joaco1993
What part of New York are you in in your origenal post you stated the motor was running at 50Hz witch was the supply
All of the US is in on motor would or pare of the grid the grid in 60Hz so a 50Hz motor would be running faster it it is on 60Hz
VFD's shipped in the US for use in the US are default set would be 60Hz
you could run a 50Hz motor at 60Hz without any problems it would just run faster
if it to be on 50Hz system it would have to be on a private system and never ever connected to the grid
for reference their is a 25Hz system in the north east US (Amtrack / Conrail ) and only used for trains.
so you origenal post is a little confusing
Click to expand...

Hi Gary, this work is in Argentina! they have 50Hz in the grid.
 

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