| 摘要 |
1407737 Automatic control of speed of electric motors SOC OPITERGINA LAVORAZIONI ELETTROPLASTICHE SpA 17 Aug 1973 [5 Dec 1972] 39105/73 Headings G3N and G3R [Also in Division H2] A permanent magnet D.C. motor for driving a washing machine is controlled to accelerate gradually to a speed where the clothes distribute themselves uniformly around the drum and subsequently to accelerate gradually to one of two selectable spinning speeds. The motor armature 1 is connected in a bridge circuit comprising resistors 2, 23, 24 with the input of the bridge connected to the controllable rectifier arrangement 73 which is supplied from tapped auto-transformer winding 5 in series with resistor 4. The changeover switches 3, 38, 39 are operated by a programmer and under washing conditions the contacts a in switches 3, 38 are closed. The reference signal at point 50 is derived from resistor 53 and is compared with the back e.m.f. of the motor to provide a signal on the base of transistor 9. Time constant circuit 7, 8 causes the conduction of transistors 12 to increase slowly thus charging capacitor 13 slowly causing the controlled device 15 to be conductive for longer in each half cycle. This increase in conduction time is passed by transistor 20 to the controllable ratifiers 36, 37 whereby the motor speed increases. The programmer now causes switch 38 to make contact b so that the reference at point 50 is increased due to the action of transistors 55, 56 and their associated circuitry. This gives a speed of 100 r.p.m. Contact 39 now operates together with a changeover of contact 3 to terminal b thereby increasing the reference signal by conduction of transistor 66 and applying the full supply voltage to the rectifier 73. Contact 39 controls the insertion of resistor 65 in circuit to give higher 800 r.p.m. and lower 400 r.p.m. spin speeds. Potentiometers 48 and 69 are used to adjust the washing and spinning speeds respectively. |
