Patent ID: 11955900
Assignee: ABB SCHWEIZ AG
Field: Electrical machinery, apparatus, energy (Electrical engineering)
Classification: CPC H | IPC H

Claim 0:
1. A bi-directional switch for an inductive machine, the bi-directional switch comprising:
a first power semiconductor transistor,
wherein the first power semiconductor transistor includes a first source, a first drain, and a first gate;

a second power semiconductor transistor,
wherein the second power semiconductor transistor includes a second source, a second drain, and a second gate, and the second source is directly connected to the first source;

a firing angle reference generator,
wherein the firing angle reference generator is configured to generate a linear ramp down from a fixed starting angle; and

a soft-starter device including a control circuit configured to provide a first control signal to the first power semiconductor transistor and a second control signal to the second power semiconductor transistor,
wherein the soft-starter device is fora three-phase load; and
wherein the control circuit generates the first control signal and the second control signal based on:
detecting a falling edge of a turn-on pulse generated by comparing a measured phase angle to a reference firing angle for each half cycle of a supply voltage,
determining a number of return path devices in one or more phases, wherein the number of return path devices is based on a state of each return path device of the return path devices, and
comparing a measured phase current with a diode threshold current, wherein the comparing of the measured phase current with the diode threshold current comprises determining a slope of the measured phase current.