The magnetic-amplifier controlled log-carriage drive and the basic duty cycle of carriage performance

The drive for the log carriage is probably the most important of all sawmill drives. The mill's output is directly related to the speed and agility with which the carriage will respond to the sawyer's needs. The carriage represents a load of high inertia, and to propell it at required degrees of acceleration, deceleration, and speed demands large amounts of power. In making electric log-carriage applications it is economic practice to load the drive units to the maximum currents for which they are capable in rapidly recurring duty-cycle operation. This paper deals with the significance of this loading as related to: 1. The cost of the drive as aifected by the production requirements of specific applications. 2. The introduction of modem magneticamplifier controls to permit loading the drive components to their maximum load capabilities. 3. The introduction of a “basic duty cycle” for carriage operation. Based on this cycle, simple equations are developed to afford better understanding and appreciation of the important factors involved Dollar cost $\sim(\rm HP)_{rms} = {{P_{m^{3}}d^{2}W} \over {86,600,000}}$ For example, this basic equation states that the cost of a drive is approximately proportional to the cube of the maximum production requirement (Pm), measured in continuous round trips per minute, that the carriage must make. Other important equations are developed, and the solution of a specific problem according to the theory is presented in graph form.