VFD for Blower
VFD for Blower
(OP)
Does anyone have a suggestion on how to prevent a blower or compressor from going into surge in a VFD application? Since the machine operates at different speeds, just looking at one pressure won't be enough. Do we also have to match speed to the pressure (or flow) at each speed curve? There must be an easier way! Can anyone help?





RE: VFD for Blower
RE: VFD for Blower
RE: VFD for Blower
Surge in compressible flow turbomachines is generally preceded by blade stall as flow is reduced from rated flow. Since airfoil blade stalling usually occurs at inlet positive incidence angles of roughly 12 to 18 degrees, surge can be expected at incidence angles higher than that.
RE: VFD for Blower
Surging is the result of the machine exceding it's rated pumping head, you either have to reduce the head pressure or increase the suction (back) pressure.
RE: VFD for Blower
If you have a system where the pressure is more or less constant as flow rate changes then the blower will stall at some point as you reduce speed. Unfortunately in these cases VFD is simply an inappropriate control. If this applies in this case will have to reinstate the IGV system.
VFD is ideal where the system resistance varies as the square of flow but are definitely not suitable in cases where the pressure does not drop off substantially with flow.