VFD nuisance tripping

[mike_kilroy]

We have sold & applied vfd's for over 35 years. Never ONCE did we take service factor into account. It is not used in sizing a vfd. If one MUST use a SF in sizing equation, then one has picked TOO SMALL a motor to begin with. Please check what 'service factor' MEANS: it means you can OVERLOAD a given continuous rated motor and LIVE with the shortened life. This is NO way to apply a motor or a vfd. No two ways about this folks.

 

[Jraef]

Someone always has to muddy the water

But I suppose the drive could have a service factor also, without one 75 kW is still 75kW.

Service Factor is irrelevant on motors run from drives. NEMA motor that say they are 1.15SF will also say they that if they are suitable for running from a VFD, are reduced to 1.0SF. In other words, there is no using the SF if running an appropriately rated motor from a VFD.

By the way, in this particular case this motor is NOT rated for operating from anything but a "sine wave", meaning it is NOT rated for running from a VFD. I wouldn't do it.

 

[Jraef]

We have sold & applied vfd's for over 35 years. Never ONCE did we take service factor into account. It is not used in sizing a vfd. If one MUST use a SF in sizing equation, then one has picked TOO SMALL a motor to begin with. Please check what 'service factor' MEANS: it means you can OVERLOAD a given continuous rated motor and LIVE with the shortened life. This is NO way to apply a motor or a vfd. No two ways about this folks.

He beat me to it... :thumbsup:

 

[Saleh]

VFD Manual

VFD Manual

What does the VFD manual say this error message means?

Most of the time the error message displayed is 5CF2 (Impedant sh circuit) or 5CF3 (Ground short circuit).
Cut of the operation manual attached.
We applied the first three recommendations of the remedy procedure and we are willing to add motor choke, my question is that enough?
Saleh

 

[kwired]

We have sold & applied vfd's for over 35 years. Never ONCE did we take service factor into account. It is not used in sizing a vfd. If one MUST use a SF in sizing equation, then one has picked TOO SMALL a motor to begin with. Please check what 'service factor' MEANS: it means you can OVERLOAD a given continuous rated motor and LIVE with the shortened life. This is NO way to apply a motor or a vfd. No two ways about this folks.

Kind of my feelings also. I have never taken service factor into account when selecting a VFD. I am seldom the one selecting the needed motor for an application, but it is my feeling that a motor with a SF over 1.0 is just one that will take 100% loading better, not that you should design it to run at 115 or 125%

 

[Jraef]

Kind of my feelings also. I have never taken service factor into account when selecting a VFD. I am seldom the one selecting the needed motor for an application, but it is my feeling that a motor with a SF over 1.0 is just one that will take 100% loading better, not that you should design it to run at 115 or 125%

Unfortunately, OEMs tend to see it differently. If they need 11.5HP, they will run a 10HP 1.15SF motor into the SF continuously rather than use a 15HP motor and have some fudge factor now. The end user suffers when the motor dies early but if it outlives the warranty, which most likely it will, the OEM is satisfied.

 

[kwired]

Unfortunately, OEMs tend to see it differently. If they need 11.5HP, they will run a 10HP 1.15SF motor into the SF continuously rather than use a 15HP motor and have some fudge factor now. The end user suffers when the motor dies early but if it outlives the warranty, which most likely it will, the OEM is satisfied.

I can say I have run into that before.

 

[weressl]

Service Factor is irrelevant on motors run from drives. NEMA motor that say they are 1.15SF will also say they that if they are suitable for running from a VFD, are reduced to 1.0SF. In other words, there is no using the SF if running an appropriately rated motor from a VFD.

By the way, in this particular case this motor is NOT rated for operating from anything but a "sine wave", meaning it is NOT rated for running from a VFD. I wouldn't do it.

I think service factor was mistakenly identified as an issue when people were thinking of efficiency. Motors are nameplated at their shaft output and drives are PRIMARILY current output rated. The motor HP/kW identification given in the catalogs are for reference and is based on the available average standard motors on the world market. (The same drive may be suitable and nameplated for different HP or kW in different regions, but it cuts down on all the different drives one would need to make for a more precise fit.)

There are products on the market that are designed to output close to sine wave output and recommended for finicky motors and perfectionists like you:lol: or me:slaphead:, but I would not be so hesitant to drive this motor with an output reactor, especially since it is so close. (Heck I shorted the windings on an old vertical 150Hp wound rotor and hooked it to an Toshiba to replace the liquid rheostat and it just loved it....GE was screaming at me: don't do it, you gonna burn it up. Happily kept singing for 10 years until I left the plant. My "thermal" safety was to literally strap an RTD on the stator winding head with heat transfer cement, hook it to a recorder and set alarms at 85C. Never seen anything over ~70's.)