Patent GB-1500319-A (GB)
Title: Apparatus for re-transferring power from mechanically driven and/or electrically braked motors of a spinning machin
IPC: B21D22/14
Filed: 1975-05-07
Abstract: 1500319 Spindle drives MASCHINENFABRIK RIETER AG 7 May 1975 [20 May 1974] 19147/75 Heading DID [Also in Division H2] The AC motors of a spinning machine, in particular a spin-drawing machine, spin-winding machine or spin-draw-winding machine, are controlled so that power is re-transferred from any one or more motors being mechanically driven and/or electrically braked to the other motors of the machine, each motor for example 12 and 13, being respectively supplied from an AC supply 1 through a rectifier 2, DC intermediate circuit 6 and inverter 8 and a rectifier 3, DC intermediate circuit 7 and inverter 9, the circuits 6, 7 being connected through diodes 15, 16 and 17, 18 to a power transfer circuit 14, whereby if motor 12 for example, is mechanically driven or electrically braked by frequency reduction, power flows from the inverter 8 through the diodes 16, 17 to the inverter 9 where it is used to drive the motor 13. Also if a rectifier 2, 3 becomes inoperative, its associated inverter is fed by the other rectifier(s) through appropriate diodes and the circuit 14. The diodes may be replaced by a resistor, preferably voltage dependent, Fig. 1A (not shown) or by two series-opposed Zener diodes, Fig. 1B (not shown). The motors may be controlled in pairs, each pair having a corresponding rectifier, inverter and DC intermediate circuit. If the supply I and rectifiers 2, 3 are three phase, Fig. 2 (not shown), positive and negative power transfer circuits (31, 32) are provided and connected through respective pairs of diodes (34, 35; 36, 37) and switches 29, 30 to the positive and negative halves (23, 24) of the corresponding rectifier bridge (22), which is connected to the supply 1 through a switch (21) gauged to switches (29, 30) to open and close therewith. To prevent over-voltage in the power transfer circuit when all the motors are stopped simultaneously, the braking of each motor is controlled by the circuit shown in Figure 3, wherein an inverter 104 controlling a motor 105 has its frequency determined by a voltage/frequency converter 103 fed from an amplifying circuit 102 connected to a frequency adjusting device 101. The voltage of the power transfer circuit 107 is compared in an amplifier 110 with a desired maximum voltage from voltage divider 122, the amplifier 110 controlling the circuit 102 through a diode 111 and switch 112. To start the motor 105, a switch 108 is closed and gauged switch 112 simultaneously opens, whereby the members 101, 102, 103 control the inverter 104 to progressively increase the frequency of the motor, until its desired speed is reached. To stop the motor, switch 108 is opened and switch 112 closes whereby, should the voltage of circuit 107 exceed the desired voltage, the amplifier 110 controls the circuit 102 to decrease the rate of frequency reduction of the inverter and hence the rate of braking of the motor, this action being continuous down to zero frequency to maintain the circuit 107 at the desired voltage. The control may be made discontinuous, that is braking of the motor in steps, by inserting resistors (124, 125) in the circuit 102, Fig. 3A (not shown) to intermittently interrupt the action of converter 103.