7 7.5 7.5.5 DC-bus operation Basic dimensioning Determining the power requirements 7.5.5 Determining the power requirements For determining the power requirements of the drive system you need to knowtheratedpowerofthemotorsandtheirefficiencyaswellasthepower losses of the controllers. The power requirements are calculated with the following formula:
P DCtotal = i = 1 ⎨⎧ ⎩ n P shaft i η i + ( P loss ) i ⎬ ⎫ ⎭ P DCtotal Total power required by the drive system P shaft Rated power of a connected motor P loss Power loss of a controller η Motor efficiency I Index variable for device identification n Number of devices in the drive system The supply unit must be able to supply the calculated power requirements. For application examples, please see 7.7 . 7.5.6 Determining the regenerative power requirements Power regeneration into the AC mains is presently not yet possible with the 9400 servo drives series. Use the regenerative power for the dimensioning of the brake chopper(s) and the brake resistor. 7.5-4 EDS94SPP101 EN 3.1-04/2007