Fractional frequency converter using zero switching of input frequency halfwaves
First Claim
1. A frequency converter is for a multi-phase electric motor comprising input means for connection to a multi-phase alternating current electric supply source, an output means for connection to a multi-phase utilization means such as a multi-phase electric motor, an SCR bridge comprising a plurality of SCRs interconnecting said input means and said output means, trigger circuit means connected to said SCR bridge for effecting selective firing of said plurality of SCRs, means connected to said input means for developing a plurality of timing pulses upon zero crossing of the input means phases, and logic circuit means interconnecting said timing pulse means and said trigger circuit means for effecting selective sequential firing of said plurality of SCRs at said zero crossings, firing of said SCRs being respectively terminated upon reversal of a respective phase.
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Abstract
A frequency converter is provided for a three-phase electric motor and has input connections for a multi-phase alternating current electric supply source, and output connections for connection to a three-phase electric motor. A SCR bridge including a plurality of SCRs interconnects the input connections and the output connections. A trigger circuit is connected to the SCR bridge for selective firing of the SCRs, in response to timing pulses generated upon zero crossing of the input means phases. Logic circuits interconnecting said timing pulse generators and the trigger circuits for effecting selective sequential firing of the SCRs at the zero crossings. Firing of said SCRs is respectively terminated by natural commutation. In one embodiment of the invention single phase current is converted to multiphase current.
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19 Claims
- 1. A frequency converter is for a multi-phase electric motor comprising input means for connection to a multi-phase alternating current electric supply source, an output means for connection to a multi-phase utilization means such as a multi-phase electric motor, an SCR bridge comprising a plurality of SCRs interconnecting said input means and said output means, trigger circuit means connected to said SCR bridge for effecting selective firing of said plurality of SCRs, means connected to said input means for developing a plurality of timing pulses upon zero crossing of the input means phases, and logic circuit means interconnecting said timing pulse means and said trigger circuit means for effecting selective sequential firing of said plurality of SCRs at said zero crossings, firing of said SCRs being respectively terminated upon reversal of a respective phase.
Specification