VSD for chiller at high lift conditions

[wta12]

Hello all,
For centrifugal chiller, many comments about reduce lift when unloading chiller - compressor speed chiller. But for VSD screw chiller (carrier, york) is this principle still working ?
Thanks

[Magoo]

generally speaking centrifugal compressors require optimum impellor tip speed to be driving force for compression, so they have variable inlet vanes to alter flow rates.
Variable impellor speeds would have compounding /negative effect of vapour flow rate through compressor. Effectively you will get slippage from high to low pressure zones, sounds horendous and prematurely damages mechanical components like thrust assemblies.