Vibration of vibration are pulling a child back on a swing and letting it go, or hitting a tuning fork and letting it ring. The mechanical system vibrates at one or more of its natural frequencies and damps down to motionlessness. Forced vibration is when a time-varying disturbance (load, displacement or velocity) is applied to a mechanical system. The disturbance can be a periodic and steady-state input, a transient input, or a random input. The periodic input can be a harmonic or a non-harmonic disturbance. Examples of these types of vibration include a washing machine shaking due to an imbalance, transportation
Per-unit system this, the base currents I and I are related in the opposite way that V and V are related, in that formula_31 The reason for this relation is for power conservation S = S The full load copper loss of a transformer in per-unit form is equal to the per-unit value of its resistance: formula_32 formula_33 Therefore, it may be more useful to express the resistance in per-unit form as it also represents the full-load copper loss. As stated above, there are two degrees of freedom within the per unit system that allow the engineer to specify any per unit