Associated Equipment - Power Stack 6-5AC30 series Variable Speed InverterDynamic Braking Resistors (optional)Dynamic Brake Resistors tend to be used when an application requires regenerated power from the motor to be dissipated.The AC30 Frame K is fitted with an internal brake switch ready for connection to an external Dynamic Brake Resistor.AC30 Frames L, M & N do not have an internal brake switch and an external brake device must be used if braking is required.Systems applications that have a number of inverters connected on a common DC bus, either from a regenerative DC supply unit or aspart of an AFE system, may not require the use of braking resistors.Where a Dynamic Brake Resistor is used, Parker recommend the addition of a thermal overload switch to be fitted in series with theresistor, in order to protect the component.CalculationThe Dynamic Brake Resistor must be rated to absorb both peak braking power during deceleration, as well as the average power overthe complete cycle. The following formulas can be used to calculate the peak and average braking power:Peak Braking PowerP pk (W) = 0.0055 x J x (n 1² – n 2²)t bAverage Braking PowerP av (W) = P pkx t bt cBrake resistors at these power levels tend to be custom solutions.Once the peak and average braking power of the application is calculated, this information will be required by the brake resistormanufacturer, in addition to a minimum resistor value that can be used. This information can be found in ‘Appendix E: TechnicalSpecifications – Power Stack’, for the Frame K only.For Frames L, M & N that require an external brake device, refer to the product Technical Manual for minimum resistor sizes.It is recommended that a large safety margin must be incorporated to ensure that the resistors are not overloaded.Refer to ‘Chapter 4: Installation – Power Stack’ for details on how to connect up the DBR to the inverter.Where:J = total inertia (kgm²)n1 = initial speed (rpm)n2 = final speed (rpm)tb = braking time (s)tc = cycle time (s)
