power flex40 motor speed

[nmk34]

i am going to ask a selly question :
is there a parameter that might change the speed of the attached motor at a givin frequency either up or down?(keeping the frequency the same)

 

[Bit_Bucket_07]

There are some drive experts here. I'm not one of them.

I think though, that in order to help you, they'll need for you to elaborate somewhat regarding your current control scheme and what it is, exactly, that you want to accomplish.

Is this a stand-alone drive that you're operating via the keypad?

 

[Ken Roach]

It's not a silly question, but rather one that invites some investigation.

In general, an AC motor spins at a speed determined by the frequency of the 3-phase power supplied to it, based on its number of poles and construction.

Are you troubleshooting a system that is not producing the motor shaft speed that you expect it to, like a conveyor that speeds up or slows down ?

Or are you trying to "trim" the motor speed based on a control loop or feature other than the Command Frequency that the drive gets from its keypad, analog input, preset, or PLC network connection ?

The more context and detail you can provide, the better !

 

[jaden]

The output frequency is what determines the motor speed. Please define further what you are wanting to do.

 

[Puddle]

Is the current nearing full load? I've seen a few drives that will attempt to slow down to reduce current, then speed back up once it's dropped.

 

[nmk34]

I raised the question because at a known frequency let say 30hz the product traveling on the conveyor used to take 4 minutes, and i checked it recently at the same frequency and it takes 7 minutes. these 3 minutes makes changes like day and night. No reports of gear box or motor changing.

 

[Steve Bailey]

Could something in the drivetrain be slipping?

At 30 Hz, a 60 Hz motor should be turning at 50% of nameplate speed. That would be the first thing to verify.

 

[DarrylR]

The load on the motor will have an impact on speed at constant frequency

 

[Bit_Bucket_07]

The load on the motor will have an impact on speed at constant frequency

It's difficult for me to believe that an overload condition that almost halved the normal speed of the motor rotation at 30 Hz wouldn't result in an overload fault.

 

[James Mcquade]

if the motor frequency is the same for the 4 minute and 7 minute test, i have to ask, What changed?

did a gear or sprocket get changed by maintenance.
did the gearbox or motor get changed
has the conveyor length changed
has the load changed
what is the conveyor? rubber belt, rollers, chain?
rubber belts do stretch.
the load can cause slippage.
sudden impact of the load onto the system causes slippage if it is heavy enough
hope this helps,
james

 

[jaden]

To check the drive, Verify the displays of Commanded and Output Hz. are close to each other. Also, check the Output Voltage. It should be approx one half voltage at 30 Hz. if the drive is in Volts/Hertz mode.

 

[cardosocea]

Not sure the powerflex40 has this capability, but power limitation functionality would do what you say.