Abstract: A controller for a motor for raising and lowering a lift car in a lift well is disclosed which comprises transistor bridge circuits (10) for providing power to said motor (m), a first processor having a multiplexer (54) for passing one of a plurality of signals containing data relating to the state of said transistor bridge circuits (10) to an analogue to digital converter (38) for converting analogue signals to digital signals and providing said digital signals to a main processor (70), a polar conversion circuit (78) for receiving said signals from said transistor bridge circuits (10) and for converting the signals into signals having a magnitude and a phase component, an overcurrent sensor (85) for sensing whether the current supplied by the transistor bridge circuits (10) is too high, said overcurrent and sensor circuit being coupled to a pulse modulator circuit (87) for controlling the pulse width of the signal applied to the transistors in said transistor bridge circuits, and a second processing circuit

Abstract: A method for controlling the speed of an AC machine (12) is described.The AC machine (12) receives three output phases (A,B,C) supplied from a cycloconverter (10) which is connected to an input supply (R,Y,B) of frequency f.sub.1. The cycloconverter (10) is caused to operate in three modes under control of a microprocessor (25).The first mode supplies the AC machine (12) in the frequency range 0 to f.sub.0, by conventional cycloconverting to generate a near continuum of frequencies.The second mode operates the cycloconverter (10) to synthesize a number of frequency steps in the frequency range f.sub.0 to f.sub.1 from the input supply (R,Y,B) and provides speed control of the AC machine (12) by phase control of the output voltage (A,B,C) between each frequency step.The third mode operates the cyclonverter (10) to be transparent, such that the input frequency f.sub.1 is effectively directly supplied to the AC machine (12) without speed regulation being applied.

Abstract: A controller for a motor for raising and lowering a lift car in a lift well is disclosed which comprises transistor bridge circuits (10) for providing power to said motor (m), a first processor having a multiplexer (54) for passing one of a plurality of signals containing data relating to the state of said transistor bridge circuits (10) to an analog to digital converter (58) for converting analog signals to digital signals and providing said digital signals to a main processor (70), a polar conversion circuit (78) for receiving said signals from said transistor bridge circuits (10) and for converting the signals into signals having a magnitude and a phase component, an overcurrent sensor (85) for sensing whether the current supplied by the transistor bridge circuits (10) is too high, said overcurrent and sensor circuit being coupled to a pulse modulator circuit (87) for controlling the pulse width of the signal applied to the transistors in said transistor bridge circuits, and a second processing circuit com

Abstract: An electrical motor has a ring with a plurality of stepped portions in at least one surface. There are plurality of C-shaped cores spaced along the ring, the C-shaped cores each having at least one surface provided with stepped portions which oppose the surface of the first member having the stepped portions. Each of the C-shaped cores has a permanent magnet and a ring providing a flux path joining the magnets.

Abstract: A power supply system (10) comprises a multi-phase AC supply (12) which is provided to an AC-DC convertor 14. The DC output from the convertor (14) sources power to a DC bus (16), which then provides power to a secondary supply bus (42) and electrical loads (38, 40). The convertor (14) is connected to the DC bus (16) by a master controller (22), which is controllable by master control processor (30) to disconnect the two. In a similar way, the secondary supply bus (44), load (38) and load (40) are connected to the DC bus (16) by slave controllers (46), which are each controllable to effect disconnection through action of the respective slave control processors (48). When any of the secondary supply bus (44) or loads (38, 40) demand power from convertor (14), a demand request is passed by the respective slave control processor (48) to the master control processor (30) via data bus ( 32).

Abstract: A transmission arrangement includes a switched resonant circuit (5) for switching data states of digital signals on a pair of transmission lines (1, 2) and a regenerative circuit (7) for feeding power back on the lines. The switched resonant circuit has a switching device (22) connected in series with an inductance (20) and parallel with a capacitance (21). A digital logic system (8) controls the switching device such that switching occurs at a line current zero crossover point. Where a change of data state is to be transmitted to a receiver (6), the logic system (8) turns the switching device on at an appropriate time. The switching device is switched off when the voltage (+Vm) on the lines reaches approximately the same magnitude in the opposite sense (-Vm). The change in the line voltage indicates a change of the data state to the receiver.