text: <s>[INST] Powerflex 525 load speed fluctuations EDIT: moved to Drives and Motion community. -FL Using a powerflex 525 2.2kW unit to drive an unblanced load with heavy interia which tends to flctuate in actual rpm. Can this be controlled with dynamic braking? [/INST] EDIT: updated broken link to the first mentioned technote -FL Hello, There are many options to be addressed when handling high inertia loads. Many generic considerations are mentioned on PowerFlex 7 series, PowerFlex 40 1336S & 1336F: Guide line :to handle a high-inertia load Dynamic braking could be an option to improve the control of a high inertia load by any variable speed drive. One of the main challenges with a high inertia load occurs when the load needs to be decelerated by the drive. The drive will try to slow down the motor by applying the deceleration ramp, but the high inertia load is going to keep pulling from the motor shaft. During that moment the motor is going faster than what the drive tells it. Typically this is referred as the motor working in regeneration. The excess of energy needs to go somewhere and flows back from the motor windings through the antiparallel diodes of the IGBTs at the inverter section of the drive, back to the DC bus. The DC bus voltage raises and normally the drive trips on DC Bus overvoltage. An external braking resistor connected at the end of the DC bus of the drive will allow for the resistor to absorb part of this excess of energy, aiming to keep a good level of DC Bus and giving the drive a chance to keep controlling the load. The process to finely size and select the breaking resistor is explained in detail on https://literature.rockwellautomation.com/idc/groups/literature/documents/at/pflex-at001_-en-p.pdf ,but it could be time consuming. There are some tables as well on the literature available from each drive with certain recommendations of suitable breaking resistor from the Rockwell portfolio that could be attempted as starting guide. The key parameters as well to set the braking resistor on the PF525 drive are documented via PowerFlex 520-Series: Dynamic Brake Resistor Parameter Settings Equally, it should not be ruled out the possibility of a more suitable drive from the portfolio capable of better handling high inertia loads. The local distributor nearby or the local Rockwell representative should be able to provide you further recommendations. Regards, \\n </s>