Abstract: Three terminal, six and twelve pulse unrestricted frequency changing circuits are provided by inserting controllable bidirectional switching circuits between open star configured coils in multiple phase windings of isolation transformers. Where the switched winding are secondaries of the isolation transformer, interphase transformers are provided between each pair of three pulse circuit groups and additional interphase transformers are required between six pulse circuit groups to provide a three terminal output. Where the switched windings are primary windings of the isolation transformer, the secondary windings are electrically connected in series with each other to provide the three terminal output.

Abstract: An inverter bridge provided with a series-network in its diagonal including an inductor and an output transformer is feedback-controlled to generate a sine wave by reference to a sine wave reference signal and in a self-oscillatory fashion of the "bang-hang" type. The series-network operates during the "hang" phase as an active filter. Transistors are used on the high frequency side of the bridge and thyristors are used on the fundamental frequency side of the bridge. Provision is made for an AC source in parallel with the load, in which case feedback control is in response to the relative shares of the sources in the common load.

Abstract: Non-dissipative filtering of a DC voltage, or current, is provided with an energy storage inductor coupled sequentially in alternate directions across the DC source. In another embodiment the inductor is part of the primary of a transformer and secondary DC voltage is derived by rectification. In a further embodiment, a thyristor and a diode respectively at opposite sides of the transformer and a capacitor at the output of the rectification unit concur in limiting the transferred DC energy to a selected level by control of the firing angle of the thyristor.

Abstract: A commutation circuit for thyristors alternately turned ON by pulse width modulation (PWM) for the generation of a fundamental sine wave is characterized by two separate primary windings associated with respective positive and negative thyristors with a common secondary winding at the output, and two commutating networks for the respective poles, each including an auxiliary thyristor for fixed-commutation and the resonant combination of a capacitor and an inductor. The thyristors, the commutating networks, the DC source, and the output transformer have a symmetrical disposition as well as symmetrical commutation steps.

Abstract: An elevator system including an elevator car to be stopped at a predetermined stopping point from any initial speed below a predetermined maximum value, at a predetermined uniform rate of deceleration. The uniform rate of deceleration determines the desired speed versus distance-to-go reference pattern, which is initiated at a predetermined fixed distance from the stopping point. If the car speed is at the maximum value, deceleration will be initiated immediately. If the car speed is below the maximum value, the car is allowed to continue at the same speed until the car speed and location of the car relative to the stopping point match a point on the reference pattern. This point is accurately determined via digital feedback and comparison circuits which start the elevator car on the desired deceleration speed pattern with zero error.

Abstract: An elevator system which includes speed control apparatus which provides an error count representing the deviation of an elevator car from a desired speed versus distance reference pattern. Both the instantaneous and cumulative errors are indicated by the error count, and both are simultaneously corrected with digital precision by direct utilization of the error count. Anticipatory control of non-linear actuators responsive to the rate at which the cumulative error is corrected makes the system time optimal.

Abstract: This invention relates generally to power inverting devices and more particularly, to static inverting devices which produce an output wave shape which closely approximates a sine wave.