VFD in a DOL Motor

joaco1993

Lifetime Supporting Member
J
Join Date
Sep 2014
Location
newyork
Posts
237
Hello everyone,

I had a 10hp 3phase motor 380V, that was connected DOL.

Now we changed it, and put a VFD. When running the motor at 50Hz which is the same frequency of the supply line, it looks the motor is running a little faster..

Is this posible ?? If we connect the motor with a VFD but put the same frequency of the line, shouldt it rotate at the same speed as if it was connected directly to line ??

Thanks!!
 
joaco1993 said:
Is this posible ?? If we connect the motor with a VFD but put the same frequency of the line, shouldt it rotate at the same speed as if it was connected directly to line ??

Thanks!!
Click to expand...


No
Want is your speed reference set at?
You using a pot? Or?
 
PLC said:
No
Want is your speed reference set at?
You using a pot? Or?
Click to expand...

Hi !

Speed reference is set at 50Hz, and its done via Keypad.

So the speed reference is set to the same frequency as the inline frequency..

Thanks
 
cardosocea said:
When you say "looks", have you measured it in any way?
Click to expand...

This motor is connected to a screw, and now we are having more Kg/hr than before.. Thats why I say it looks its running faster..

I wanted to know if there is a theoric reason for this to happen ??

Or if this is impossible.

The question is a motor running DOL with the line frequency of 50Hz, and the same motor running with a VFD and the Speed set to 50Hz also. Should they run at the same speed ?? or there might be a reason/parameter or whatever in the VFD that could cause to be a speed difference ??

Thanks!!
 
Is it possible that it was connected in star/wye before when it was on DOL and now it is in triangle/delta?
 
m_turk said:
Is it possible that it was connected in star/wye before when it was on DOL and now it is in triangle/delta?
Click to expand...

Hi !

Actually the motor before was started using a WYE/DELTA starter.

When we installed the VFD we connected the motor in DELTA.

So the connection is the same as before when running in normal conditions.
 
If your new VFD uses sensorless vector control, it could be compensating for slip, making the motor spin at a true 50Hz instead of 50Hz minus slip which is what the DOL starter would be doing.

What is the brand/model of VFD?
 
rupej said:
If your new VFD uses sensorless vector control, it could be compensating for slip, making the motor spin at a true 50Hz instead of 50Hz minus slip which is what the DOL starter would be doing.
Click to expand...

Hi rupej !

It is configured V/f mode..

Could you explain me a little bit more that point you are making ??

thanks!
 
rupej said:
Basically with slip compensation, the VFD knows the slip of the motor, so it outputs a slightly higher frequency to compensate, causing the motor to actually rotate at the commanded frequency. See attached document.

https://mobile.yaskawa.com/delegate/getAttachment?documentId=AR.AFD.01&cmd=documents&documentName=AR.AFD.01.pdf
Click to expand...

Ok,, but the mode im using is V/Hz.. in this mode also applies what you are saying ??

In VFDs this slip compensation is always done ? or is a parameter that needs to be configured..

I have configured many VFDs and never had to touch this parameter of slip compensation.. (but also never had this problem ! haha)

thanks!
 
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?
 
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...

Im using WEG CFW500 10HP 380V
 
Yeah, that has sensorless vector as an option but V/Hz is the default.

Where in NY do you have 50Hz? Or are you working remotely?

The only other thing that comes to mind is that if the line frequency is actually less than 50Hz (Maybe in a third-world country?) then the VFD outputting a true 50Hz would make the motor spin faster.
 

Similar Topics

S
IE5 ABB motor and VFD
Hello, It is mandatory to use VFD IF i use IE5 electrical motor? What happens If connect it directly as delta without VFD? Please look at motor...
Replies
1
Views
100
kamenges
K
S
How to setup vfd speed based on job per hour
Hello, I am trying to setup on plc so If I enter 60 jph (job per hour) it will send the vfd hertz based on what jph is entered by...
Replies
2
Views
148
sukigill
S
H
comment communique siemens s7-1200 avec vfd delta
commentaire communiqué siemens s7-1200 avec vfd delta ? (cablage et sur tia portal )
Replies
0
Views
81
houssem02
H
A
RS-485 communications with FX1N PLC and a VFD
Hello, I'm trying to delve a little into rs-485 communications for a couple projects of mine. Until now I've been using a delta vfd and a delta...
Replies
2
Views
105
Riyas Mohamed
R
T
Power Flex 525 did not run while the PLC command and VFD ready
I have an issue with Power Flex 525 during running processing, the VFD stopped suddenly while the PLC and VFD connection ok, VFD does not have any...
Replies
1
Views
106
jridge
J
Back
Top Bottom