Abstract: In the prior art it is known to determine the density of a roll of paper as it is being wound on a paper receiving roll. The determination is made each time the paper receiving roll makes a constant predetermined number of revolutions. Because the diameter of the paper on the paper receiving roll increases, there is an increasing length of paper added between successive determinations. This makes it more difficult to maintain a desired roll density by controlling various factors during winding. In addition, because the paper web is usually fed onto the roll at a constant rate, the time between successive density determinations increases. The system of the invention provides for an adjustment of the predetermined number of revolutions between density determinations. This number is decremented to provide, very approximately, the same time interval between successive determinations.

Abstract: This invention relates to a system for protecting an amortisseur winding during the starting of a synchronous motor. The system compares the actual slip frequency of the accelerating motor with predetermined slip frequencies. These predetermined slip frequencies are each associated with a timer which measures successive time segments. Each timer is stopped when the actual slip frequency, which decreases as rotor speed increases, is less than the associated predetermined slip frequency. When the timer is stopped a successive timer is started. In this manner the acceleration of the motor is broken up into time segments. The initial timer is started when the motor starts. The final timer is stopped when the rotor field current is applied to bring the motor into synchronism. Should any timer be permitted to have its timed segment expire before being stopped, the motor is shut down. There is also provided a thermal memory which receives information from the expired timer as to its associated slip frequency.