| 摘要 |
1,241,330. Control of two motors. ALLMANNA SVENSKA ELEKTRISKA A.B. 18 Dec., 1968 [19 Dec., 1967], No. 60191/68. Heading H2J. [Also in Division G3] In a timber-grinding mill, an asynchronous motor 11 drives a grinding-stone, the logfeeding chains being driven by a direct current motor 13. Signals proportional to the voltage and armature current of the motor 11 are fed to an emitter 17 providing a pulse train whose frequency represents the power consumption of the motor. The output signal from the emitter 17 is compared with a reference signal, and the difference signal controls the speed of the motor 13. The difference signal also actuates a counter 28 for indicating the power-consumption of the mill, data processing, or for control purposes. Voltage peaks are prevented from influencing the counter by means of a discriminator 21 which responds when the difference signal exceeds a set value to block AND gates 24, 25. An analogue signal proportional to the speed, voltage, or power of the motor 13 is converted into a frequency-signal, and, when a no-load peak is absent, the output signal from the gate 24 is integrated in the counter 28 to represent the quantity of wood fed to the mill. A powersignal is supplied to the counter through gate 25, which is also blocked when there is a no-load peak, and is integrated to constitute a measurement of grinding energy. In a modification, the power consumption of the stone-driving motor is detected by a magnetostrictive torque gauge whose output signal is divided by a signal representing the amount of wood fed to the mill. The latter signal is derived from a digital converter and integrator, the integrated signal being passed through an AND-gate, having a blocking circuit, to a mean value converter. The signal from this converter is proportional to the quantity of wood per unit of time, the length of the measuring period being set by a time switch. The signal from the divider is applied to a recorder which registers the grinding energy consumed per cubic metre of wood fed to the mill, Fig. 2 (not shown). In a further embodiment, signals representing the power of the stone-driving motor and the rate of feed are applied to respective mean value units associated with a divider and a recorder, Fig. 3 (not shown). |
