Hi !
I have an application where a vibratory conveyor is driven by 2 agitators.
In order to change the transport direction slightly (for sorting the material on the conveyor), the agitators are driven by VFDs that drive the motors at a slightly different frequency (f.ex. 49.5 Hz and 50.5 Hz). That cause the agitators to run at the same speed (due to the mechanical coupling), but a difference in the angle, which in turn causes a slight angle of the conveyors transporting direction.
Since one agitator is essentially driving and the other braking, the braking VFD has to send a lot of energy to a brake resistor.
This all works OK, but the brake resistor has to be much larger than normal, since it has to bleed off energy constantly rather than only when stopping.
This in turn also means I do not have much room for adjusting the frequency, since the resistor may overheat (despite being dimensioned much greater).
So I am pondering if it could pay off to connect the DC-bus of the 2 VFDs.
The idea being that the braking VFD sends the energy to the driving VFD, and thus do not have to bleed it off in the resistor.
I have heard of this principle, but I have no experience, and I would like to hear from anyone with experience or links to instructions regarding this.
Anything to be aware of ?
The VFDs are Siemens G120. Do some parameters have to be adapted when connecting the DC-bus ?
I have an application where a vibratory conveyor is driven by 2 agitators.
In order to change the transport direction slightly (for sorting the material on the conveyor), the agitators are driven by VFDs that drive the motors at a slightly different frequency (f.ex. 49.5 Hz and 50.5 Hz). That cause the agitators to run at the same speed (due to the mechanical coupling), but a difference in the angle, which in turn causes a slight angle of the conveyors transporting direction.
Since one agitator is essentially driving and the other braking, the braking VFD has to send a lot of energy to a brake resistor.
This all works OK, but the brake resistor has to be much larger than normal, since it has to bleed off energy constantly rather than only when stopping.
This in turn also means I do not have much room for adjusting the frequency, since the resistor may overheat (despite being dimensioned much greater).
So I am pondering if it could pay off to connect the DC-bus of the 2 VFDs.
The idea being that the braking VFD sends the energy to the driving VFD, and thus do not have to bleed it off in the resistor.
I have heard of this principle, but I have no experience, and I would like to hear from anyone with experience or links to instructions regarding this.
Anything to be aware of ?
The VFDs are Siemens G120. Do some parameters have to be adapted when connecting the DC-bus ?
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