Abstract: A drive system comprises a brushless multi-phase motor which is supplied with power by way of an inverter including thyristors which are fired by a firing network. The firing network is supplied with information relative to the position of the rotor of the motor, by means of a transducer and this information flows by way of a logic network. Also provided is a current sensing device, a signal from which is passed through a control network to the logic circuit, and the logic circuit acts to modify the signals applied to the inverter in the event that the current flowing in one of the d.c. supply lines to the inverter exceeds a predetermined value for more than a predetermined length of time.

Abstract: A brushless A.C. synchronous motor includes a stator assembly having a stator winding and an inverter for feeding the stator winding, a rotor assembly including a field winding and a transformer having a primary winding on the stator assembly and a secondary winding on the rotor assembly. The primary winding is fed by an oscillator on the stator assembly, and the secondary winding provides an output for the field winding by way of rectifier.

Abstract: An electrical inverter comprises positive and negative supply lines across which is connected a first series circuit including the anode-cathode path of a first thyristor and the anode-cathode path of a second thyristor. A second series circuit bridges the supply lines and includes a pair of capacitors. In addition a commutating circuit is provided for the first and second thyristors, and this includes a transformer having a secondary winding connected between a point intermediate the first and second thyristors, and the capacitors of the second series circuit, and the primary winding of the transformer is connected in a series circuit, one end of which is connected to the point intermediate the first and second thyristors. The arrangement is such that when the commutating circuit is operated, current flow in the primary and secondary windings of the transformer acts to reduce the current flowing in the conducting thyristor to zero.

Abstract: A brushless a.c. synchronous motor comprises a stator assembly having a stator winding which is supplied with power by an invertor. The main input power to the invertor flows through the primary winding of a transformer the secondary winding of which supplies current by way of a rectifier, to a field winding of the rotor assembly of the motor.

Abstract: An electrical inverter comprises first and second supply lines, which in use are connected to the positive and negative terminals of a d.c. supply. An inverting network is connected between the supply lines and has output terminals for connection to the load. A current sensing device is provided in one of the supply lines and is operable when the current flow in the supply line exceeds a predetermined value, to stop current flowing in the load for a predetermined period of time.

Abstract: An electrical inverter comprises positive and negative supply lines, first and second thyristors the anodes of which are connected to the positive line and the cathodes of which are connected respectively to the anodes of third and fourth thyristors. An oscillatory commutating circuit including a capacitor and an inductor is provided and which is connected between the anodes of the third and fourth thyristors and also a firing circuit is provided to provide gate signals to the first, fourth, third and second thyristors in that order. In addition, means is provided to over-damp the oscillatory circuit thereby to limit the commutating voltage.