VFD to a conveyor - Problem with load and current
VFD to a conveyor - Problem with load and current
(OP)
Hi
I am testing a screw conveyor to check the power requirements for different materials. The screw conveyor is being fed by a slower screw as is shown in the attached link/image. Both the screws have a different inverter controlling the speed.
http://www.gliffy.com/publish/2215116/
I am having a little problem with the elevator inverter. Its a 380-400V, 50/60Hz, 16 A (pk) Input with
0-500 V, 9.5A, 4kW, 3 phase Output.
The motor at the end of the screw is 3 kW, 6.3-6.8 A, cos (phi) = 0.78. The max spped is 2860 rpm with a gear reduction of 10 at the end. So the max speed is taken as 286 rpm at 50 Hz. Its a two pole three phase motor.
The V/Hz ratio is almost 8.
Q1) When I am testing the material, the empty current load shown by the inverter is 3.8A and when I start feeding in material the load drops to 3.7A. Any idea why it is doing that?? I have tried it three times as well. The inverter frequency is 10 Hz at this point.
Q2) Why is the current almost stable after 20 Hz? I know that the voltage is changing and thus the power too but wanted to confirm if this makes sense.
Any help would be appreciated. The graphs below show the info ive found using testing.
Thanks
J
htt p://files. engineerin g.com/getf ile.aspx?f older=4e5a 9dbc-e433- 4b82-b1fd- e358805911 43&fil e=Test_Res ults-2.pdf
http://fi les.engine ering.com/ getfile.as px?folder= 722496c1-0 35b-4b59-8 44b-fff9da a2b585& ;file=Test _Results_C hart_1.pdf
I am testing a screw conveyor to check the power requirements for different materials. The screw conveyor is being fed by a slower screw as is shown in the attached link/image. Both the screws have a different inverter controlling the speed.
http://www.gliffy.com/publish/2215116/
I am having a little problem with the elevator inverter. Its a 380-400V, 50/60Hz, 16 A (pk) Input with
0-500 V, 9.5A, 4kW, 3 phase Output.
The motor at the end of the screw is 3 kW, 6.3-6.8 A, cos (phi) = 0.78. The max spped is 2860 rpm with a gear reduction of 10 at the end. So the max speed is taken as 286 rpm at 50 Hz. Its a two pole three phase motor.
The V/Hz ratio is almost 8.
Q1) When I am testing the material, the empty current load shown by the inverter is 3.8A and when I start feeding in material the load drops to 3.7A. Any idea why it is doing that?? I have tried it three times as well. The inverter frequency is 10 Hz at this point.
Q2) Why is the current almost stable after 20 Hz? I know that the voltage is changing and thus the power too but wanted to confirm if this makes sense.
Any help would be appreciated. The graphs below show the info ive found using testing.
Thanks
J
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