vfd over current tripping issue

[leslyaj007]

We used 30kw vfd for 30kw motor.it is operated from DCS. When we start the motor its tripping. Its shows over current trip on vfd. After reset on vfd its starts normaly. Sometimes trips 3 or 4 times then its starts.its happens only on startup. Motors, connections were checked. No issues found.now other vfd motors also tripping on startup. What may be tha issue please ans...

 

[GoldDigger]

Any chance that the motors are already rotating (either forward or backward) at the time the Start command is given to the VFD? That can cause excess current if the VFD is not designed and properly configured to support a "flying" start.

 

[leslyaj007]

No its not rotating

 

[Jraef]

Is it rotating the SECOND time you restart?

What is the load and how is it configured? For example if it is a blower and the dampers are open, the OL may be caused by a starting condition that is not supposed to be happening, meaning the damper control is not working properly.

 

[leslyaj007]

We have 7 vfd drives. All grounds are connected in series. Will it cause any problem?

 

[MrJLH]

Pump Application ?

 

[leslyaj007]

Pump Application ?

For bucket elevator

 

[Besoeker]

For bucket elevator

Tried making the ramp time longer?

 

[kwired]

Tried making the ramp time longer?

Or even a variable torque setup when a constant torque setting is needed.

 

[Jraef]

We have 7 vfd drives. All grounds are connected in series. Will it cause any problem?

Horrible idea, the common mode noise issues would be chaotic and might be getting into the control boards of the drives. Ground conductors with power electronics are not just for safety purposes, so acceptable practices in normal wiring are generally not acceptable in VFDs. Always read the installation manuals and follow the manufacturer instructions.

But no way to tell if this is related until you fix it and see if the problem goes away.

 

[Chelny]

We used 30kw vfd for 30kw motor.it is operated from DCS. When we start the motor its tripping. Its shows over current trip on vfd. After reset on vfd its starts normaly. Sometimes trips 3 or 4 times then its starts.its happens only on startup. Motors, connections were checked. No issues found.now other vfd motors also tripping on startup. What may be tha issue please ans...

As a variant, you screwed with VFD's rated power selection. Since elevators belong to HO applications, you had to select, at least next size of VFD. e.g. 37~45 Kw (HO) rated power VFD.

Because, from my experience, an equation:

[SIZE=4]rated power fvd = rated power of motor[/SIZE]

is working for LO applications.


Chelny

 

[ptonsparky]

I'm drawing a blank...HO...LO...?

High Output...Low Output??

 

[Chelny]

I'm drawing a blank...HO...LO...?

High Output...Low Output??

Of course... nothing special, that are common terms. Who is interested in that.You can find their explanation here in this amusing doc: https://support.industry.siemens.com/cs/document/23810411/sinamics-g110-g120-(cu-2x0x)%3A-what-does-ct-and-vt-mean-what-does-ho-and-lo-mean-?dti=0&lc=en-WW

 

[kwired]

Of course... nothing special, that are common terms. Who is interested in that.You can find their explanation here in this amusing doc: https://support.industry.siemens.com/cs/document/23810411/sinamics-g110-g120-(cu-2x0x)%3A-what-does-ct-and-vt-mean-what-does-ho-and-lo-mean-?dti=0&lc=en-WW

Didn't click on your link, but just in the wording in that link it probably is talking about constant torque vs variable torque applications - which are more commonly used terms to describe this as well.

 

[Jraef]

Of course... nothing special, that are common terms. Who is interested in that.You can find their explanation here in this amusing doc: https://support.industry.siemens.com/cs/document/23810411/sinamics-g110-g120-(cu-2x0x)%3A-what-does-ct-and-vt-mean-what-does-ho-and-lo-mean-?dti=0&lc=en-WW

So it's the same as Constant Torque (CT) rating vs Variable Torque (VT) rating as we call them in this country. Nobody else uses HO and LO over here, but as with many things Siemens, they want the entire world to use THEIR terminologies... :huh:

The OP never indicated whether he bought CT or VT rated drives, only that the loads are Bucket Elevators, which would definitely be CT. So yes, it's POSSIBLE that he bought VT rated drives and applied them to CT loads, but we can't assume that is the case.

 

[Besoeker]

As a variant, you screwed with VFD's rated power selection. Since elevators belong to HO applications, you had to select, at least next size of VFD. e.g. 37~45 Kw (HO) rated power VFD.

In my experience, the VSD is rated as 30k. You just to make sure you specify CT (HO) or VT (LO). That will rate the drives differently without having to guess at the difference in ratings.

 

[Chelny]

So it's the same as Constant Torque (CT) rating vs Variable Torque (VT) rating as we call them in this country. Nobody else uses HO and LO over here, but as with many things Siemens, they want the entire world to use THEIR terminologies... :huh:

It doesn't matter whether it called LO/HO (by Siemens) or ND/HD (by Yaskawa). Both are world known and their products are widely used in industry.

The OP never indicated whether he bought CT or VT rated drives, only that the loads are Bucket Elevators, which would definitely be CT. So yes, it's POSSIBLE that he bought VT rated drives and applied them to CT loads, but we can't assume that is the case.

Whether that's the case or not, let OP decide. :thumbsup:

Chelny

 

[Shortcircuit79]

Load

Load

Is the elevator empty at start up? how tall is it?
could have "amount of overhung load" which could look like a locked rotor .
Most VFD of soft starts have a boost which could help to get the load moving and the allow the drive to complete its start curve.

 

[kwired]

Is the elevator empty at start up? how tall is it?
could have "amount of overhung load" which could look like a locked rotor .
Most VFD of soft starts have a boost which could help to get the load moving and the allow the drive to complete its start curve.

Good question. My experiences with these is you never want them to stop while still loaded. Most I have been around never have any anti-reverse type of mechanisim so that maybe helps some, but still may not have enough torque to accelerate a loaded leg with default settings of most drives. Most I have been around were always across the line started - so you get pretty high torque immediately when leg is loaded, but it still can only do so much and if it is backed up enough, you are likely going to have to manually clean it out to some extent before it can start. Which is reason majority of these that I have been around have a meter installed to tell operator how much it is loaded - they need to regulate whatever the supply is accordingly so it don't shut down due to overload and cause such a mess, and it is also always the last item to get turned off after it has been emptied.

 

[Jraef]

Well, the OP from Sri Lanka only logged on for that one day and hasn’t been back since, so it’s likely he didn’t get the simplistic answer he was looking for and went to find it somewhere else.