| 摘要 |
<p>1,207,042. Frequency - detectors; transistor bi-stabie circuits. GENERAL ELECTRIC CO. 26 Jan., 1968 [28 Feb., 1967], No. 4336/68. Headings H3A and H3T. [Also in Divisions G1 and H2] A speed control for a motor 10 (see Division G1N) comprises a frequency sensitive switch in which one rotor winding is connected through a rectifier 38 to a capacitor 54, the emitter of a unijunction transistor 48 and across its two bases. Thus, just before the end of each halfwave pulse of rectified rotor voltage, the accumulated charge on capacitor 54 in associated with the interbase potential cause transistor 48 to fire. Transistor 56 is thus saturated whereby capacitor 60 discharges through diode 62, allowing capacitor 68 to discharge through diodes 76, 78 and transistor 84. When transistor 56 is again blocked, capacitors 60, 68 are recharged at a constant current rate via transistor 66. If the frequency is low, as it normally is, the voltage across Zener diode 78 does not fall below its breakdown value and transistor 84 continues to conduct. If however the frequency uses due to increased slip, the voltage across capacitor 68 is insufficient to produce breakdown of diode 78, transistor 84 is blocked, followed by blocking of transistor 90. When transistor 90 is conducting it powers the unijunction oscillator 94, whose output is fed to an SCR 104, whereby it fires and energizes a relay 32, whose contacts 30 introduce resistors 28a-28c into the rotor winding circuit. The slip speed at which relay 32 is energized is predetermined by adjustment of variable resistor 64 in the charging circuit of capacitors 60, 68.</p> |
