초록 ▼

AC mains voltage input is directed to a bridge rectifier and converted to a DC voltage output. This DC power supplies an inverter which reconverts it to variable frequency AC output, used to drive a variable-speed AC motor. A microprocessor-based control unit generates firing pulses for SCR\s in bot

AC mains voltage input is directed to a bridge rectifier and converted to a DC voltage output. This DC power supplies an inverter which reconverts it to variable frequency AC output, used to drive a variable-speed AC motor. A microprocessor-based control unit generates firing pulses for SCR\s in both the rectifier and inverter. It maximizes the efficiency of the rectifier by generating phase delay and sequencing data in advance of each line-to-netural zero-crossover of the AC mains voltage input; it makes the voltage and frequency of the inverter AC output both proportional to the value of the DC voltage output, enabling the system to maintain a constant volts/Hertz ratio between the AC output voltage and the AC output frequency. Appropriate fault protection circuits are included with the control unit to prevent fault conditions from damaging the system.

대표청구항 ▼

Apparatus for controlling the speed of an AC motor which is powered by a multi-phase AC input, said apparatus comprising: a plurality of bridge rectifier SCR means respectively arranged to receive the input phases of the AC input and to supply a DC output in response thereto; a plurality of inverter

Apparatus for controlling the speed of an AC motor which is powered by a multi-phase AC input, said apparatus comprising: a plurality of bridge rectifier SCR means respectively arranged to receive the input phases of the AC input and to supply a DC output in response thereto; a plurality of inverter SCR means arranged in auxiliary commutated inverter configuration for converting said DC output into an AC output having a frequency proportional to said DC output, said inverter SCR means including a connecting means for supplying said AC output to the AC motor; and control means for generating bridge rectifier SCR conduction and sequencing data, said control means including a timing means for generating zero-crossover signals which track the line-to-neutral zero-crossover points of each phase in the AC input, a first computing means connected to said timing means for generating bridge rectifier SCR sequencing data which serves to identify the particular bridge rectifier SCR means in said plurality of bridge rectifier SCR means associated with each half cycle of each AC input phase in advance of gating said particular one of said bridge rectifier SRC means into conduction and a second computing means connected to said timing means for generating bridge rectifier SCR conduction data for each half cycle of each AC input phase in advance of the first line-to-line zero-crossover point for that half cycle, said bridge rectifier SCR conduction data serving to specify the conduction point in each half cycle of each AC input phase at which particular bridge rectifier SCR means associated with that half cycle is gate into conduction, said control means also including a bridge rectifier gating means connected to said timing means for gating the bridge rectifier SCR means on and off in accordance with said bridge rectifier SCR conduction and sequencing data.