weressl
Esteemed Member
Sorry, but that should NEVER be a normal operating mode.
VFD controlled by a starter
- Thread starter mull982
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Sorry, but that should NEVER be a normal operating mode.
Cold Fusion
Senior Member
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- way north
I've always considered that 240.9 (2005) limited thermal overloads to use in motor circuits. However, I have had at least one knowledgable person agree with you.
cf
weressl
Esteemed Member
Yes, but under normal stopping conditions (as opposed to loss of supply) you'd remove the drive enable before dropping the input contactor so the VFD doesn't think it should be running. That's what we do when we use an input contactor - plus the aux. supply of course.
Loss of supply is a different matter and needs to be considered from a different perspective. On restoration of power, the VFD would not usually report a fault condition so wouldn't need a reset - it isn't greatly different from initially applying power to a healthy system. But you may not want an automatic restart of the motor without manual intervention and for that you may want lockout with a manual reset, either locally or remotely.
It was in my mind that this isn't complex, but it's routine work for us.
So, I do take your point about it requiring application knowledge. And that may not be quite so routine for others in different fields.
Cold Fusion
Senior Member
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That confuses me a bit. I have always considered a front panel button marked, "RESET" is designed to be used for a local fault reset.
cf
Cold Fusion
Senior Member
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- way north
No, they weren't another dummy - just wrong.:grin:Phew.... I was worried that it was just another dummy......
cf
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- Wisconsin
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- PE (Retired) - Power Systems
A listed combination starter is not a listed branch circuit protective device.
What sizing tools would you use to choose the correct Overload Relay element for a non-motor load? I know they are primarily for short circuit protection, but have you ever seen any VFD literature that does not have a suggested fuse or thermal magnetic circuit breaker as the input protective device?
As an example.That confuses me a bit. I have always considered a front panel button marked, "RESET" is designed to be used for a local fault reset.
cf
In unmanned water treatment works, control is from a central location. A front panel reset could be fifty miles away. Unacceptable if that's just for a reset with no fault other than loss of supply.
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- San Francisco Bay Area, CA, USA
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- Electrical Engineer
While I agree with the rest, I'm not so sure the last part of that statement (the part I highlighted) is valid. IIRC, the acceptability of an MCP is only as part of a listed motor controller. What I question is, is an existing upstream motor starter still considered as such if the VFD is placed in between it and the motor? Other sections of the NEC dealing specifically with VFD installations would indicate that they are to be treated as separate systems. That makes me believe that the OCPD of a VFD must be a full UL489 listed MCCB or fuses.
Cold Fusion
Senior Member
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Bes -
Really should read the whole quote ...:smile:
On this particular one, that issue only comes up if there is a someone in the plant (tech maintenance, screwy engineer
) in the plant fooling with the CBs. Other than that, if the utility power did go down, the control system does a nice orderly power up.cf
I was responding to what you quoted in post #25 and I included all of what you said there in my response.
"That confuses me a bit. I have always considered a front panel button marked, "RESET" is designed to be used for a local fault reset.
cf"
Nothing about remote reset in that..........so which part didn't I read?
:wink:
hillbilly1
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- Owner/electrical contractor
If your just leaving the starter in for control conveince, I would just bypass it, use a relay that has a coil voltage matching the exsisting starter coil, use the dry contact from the relay to drive the two wire control input of the VFD. Problem solved.
Cold Fusion
Senior Member
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- way north
Hummmm (sounds of deep thought) Ahhhhh .(throat clearing sounds while coming up with something that is not demeaning and only mildly teasing) ...... How about the part in posts 15, 21, 25, and 30 that say, "or remote input" But I'll bet you already knew that.
cf
weressl
Esteemed Member
That confuses me a bit. I have always considered a front panel button marked, "RESET" is designed to be used for a local fault reset.
cf
He said that pressing the RESET button should be no problem after stopping the motor.
I am saying that a RESET button should never be part of a normal on/off operation.
This is especialy true when it is a remote reset, when the operatior has no idea what he is re-setting.
In general, not just concerning this post, I wonder how much actual operating experience some of the commentors have. Not engineering, designing and starting up, but being responsible for the day-to-day operation and maintenance. Some of the comments seem to be lacking in the perception of actual effects on safety, practicality, reliability and predicable, simple operation.
weressl
Esteemed Member
An MCP and an overload is the functional equivalent to a single MCCB. The creating of the MCP came from the realisation that the thermal element is duplicated when in a combination starter a thermal overload(or SS) protective relay is employed with an MCCB that has both magnetic(short time) and thermal(long time) overcurrent protective elements. Incidentaly in EU they went the other way for a while where they would couple the adjustable thermal element with the magnetic only circuit breaker.
Cold Fusion
Senior Member
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- way north
Wer -
My confusion quotient is rising. Who "he"? And when did he say, "...pressing the RESET button should be no problem after stopping the motor."
Wer -
Not only is it "especially true", it's un-equivocally true, un-categorically true, most-assuredly .....
Possibly even an axiom of the Laws of God and Physics.
Anybody with actual operating experience knows that.
cf
weressl
Esteemed Member
Operators can be and are trained to perform reset within guidelines sufficently detailed for their understanding. Those guidelines are to include what needs to be done BEFORE reset of certain trouble messages and when things should be investigated in depth by individuals qualified for higher level of troubleshooting. Even a simple overcurrent overload could be troubleshot by an operator, say viscocity increased that causes OL and at slower speed it should be OK.
Indeed.
We generally include a POR (power on reset) relay so that restoration of power will reset fault circuits that are latched in a fail safe mode. To be fail safe, fault relays are normally energised and held in by an auxilialry contact of that relay. Obviously, on loss of power, they will drop out. The POR relay picks them up - unless there is still a fault.
Neither remote nor local reset will fix that.
please consider line reactors
please consider line reactors
are you using vfd grade cables if not, you do need reactors is the motor winding inverter duty?,not a problem to leave starter done it many times ensure proper rewiring of control circuit for starter to release control voltage to vfd can give problems depending on the features of the vfd
please consider line reactors
are you using vfd grade cables if not, you do need reactors is the motor winding inverter duty?,not a problem to leave starter done it many times ensure proper rewiring of control circuit for starter to release control voltage to vfd can give problems depending on the features of the vfd
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