Bigger Variable Speed/Frequency Drive

Probably not.

Make sure the fuses protect the cable!

The VSD probably won't be able to sense overload current (say 2A) to the motor, unless there is a separate setting for overload current. Be sure to check the full menu of parameter settings. You could also run the motor wiring through a standard overload relay or motor circuit protector.

Hi Danny,

In a word:- No.

If your motor/drive train has a problem, you will probably fry the motor.

If this is very, very temporary, just keep your fingers crossed.

I have seen worse - fuses replaced with nails etc, anything to "just make it work", so I understand the pressure, but it is not a good plan. Did you consider a fixed starter as a temporary measure? Presumably "variable" is the clue you can't.

Good luck.

Thanks Guys, that was very helpfull. I will go for JRaef's Idea of adding an overload.

Can somebody please explain technically why the VSD can't protect the motor because the overload setting parameters is correctly sets on the VSD (1.85Amps)?

If it allowed you to set it that low, but does not allow you to tell the drive that the motor is any smaller than 3kW, then that is indirectly letting you know that the protection is likely compromised. Some do a better job of making that clearer than others, often times they will just not allow you to set the motor current lower, it's just a design decision at some point. There may be a tiny print footnote inside of the manual someplace that warns you of this, or tells you that you must use an external OL relay if used on a motor smaller than 3kW, everyone approaches it differently.

just add an overload and feedback it to VFD/vsd as trouble input to complete shutdown.

in case if you will add an overload ,that will protect the motor only but will never stop to the vfd so it will be better to give a feedback to vfd to stop all ,good luck.

Hi,

The VSD uses the kw to create a typical thermal model of the motor, using the parameters include motor FLC, kW and Voltage. Even though you can set the current the VSD most likely will not be able to correctly model you motor, and like the others have mention, it will compromise your motor protection.

Adding an external overload is a way around this, but not all overloads will work correctly on the output of a VSD. I had quite a bit of trouble running multiple motors of one large VSD and the overloads were ineffective when set to FLC. In fact we ended up setting them to 70% of FLC.

Cheers.

Trevor

No problem..Tornado and Jraef got my rate good answers. Just follow what they said for the motor protection, standard package 11KW VFD will not be able to sense overload, it will result a burnt motor. It might have been different if you use under rated vfd with what is on contract(0.75KW)

• "Adding an external overload is a way around this, but not all overloads will work correctly on the output of a VSD. I had quite a bit of trouble running multiple motors of one large VSD and the overloads were ineffective when set to FLC. In fact we ended up setting them to 70% of FLC."
  

To this point by the way, there is mounting evidence supporting the idea that bi-metal overload relays do not function correctly in PWM outputs of VFDs. It's not that they fail to trip, it's that they NUISANCE trip. Then because of this, users tend to "turn up the dial" to make the issue go away, but that means that there is virtually no realistic coordination of the trip curve you end up with and the true thermal damage curve of the motor windings, resulting in the loss of the motor. The point is, either live with the nuisance or use something else, don't re-engineer the relay on your own and expect the motor to be protected.

Side note, eutectic melting alloy overload relays have no issues with harmonics.