Unity input displacement factor frequency changer

Claim 2

An AC to AC frequency changer apparatus for developing an AC output voltage across a load, comprising, in combination, an AC input power source, converter circuit means including a plurality of ON-OFF conduction controlled bi-lateral switching means operatively coupled between said AC input power source and said load, said converter circuit means comprised of a first and second converter circuit, a first conduction control circuit for controlling the conduction of said ON-OFF bilateral switching means associated with said first converter circuit to develop a first output voltage waveform and to produce an input phase angle for said first converter circuit of the same polarity as the load phase angle, second conduction control circuit means for controlling the conduction of said ON-OFF bilateral switching means associated with said second converter circuit to develop a second output voltage waveform and to produce an input phase angle for said second converter circuit of a polarity opposite to the polarity of said load phase angle, and means for combining said first and second output waveforms to form said AC output voltage across said load, the combination of said first and second converter circuits resulting in a net zero input phase angle for said converter circuit means, and consequently a unity input displacement factor for said converter circuit means.

Claim 3

An AC to AC frequency changer apparatus as claimed in claim 1 wherein said first conduction control circuIt means establishes a switching frequency for said ON-OFF conduction controlled bi-lateral switching means associated with said first converter circuit that is lower than the frequency of said AC input power source.

Claim 4

An AC to AC frequency changer apparatus as claimed in claim 1 wherein said second converter circuit means establishes a switching frequency for said ON-OFF conduction controlled bi-lateral switching means associated with said second converter circuit that is higher than the frequency of said AC input power source.

Claim 5

An AC to AC frequency changer apparatus for developing an AC output voltage across a load, comprising, in combination, an AC input power source, a converter circuit means including a plurality of ON-OFF conduction controlled bi-lateral switching means forming a first and second converter circuit, each converter circuit having a pulse number P, wherein P represents the number of bi-lateral switching means employed in each converter circuit, said first and second converter circuits being operatively connected between said AC input power source and said load, each of said bi-lateral switching means being capable of conducting current in both directions between said input power source and said load, first conduction control circuit means for generating a first conduction control signal to control the ON-OFF conduction controlled bi-lateral switching means associated with said first converter circuit, each bi-lateral switching means of said first converter circuit being rendered conductive by said conduction control signals for a period of time, T1, to develop a first output voltage waveform having a fundamental frequency component represented as fo (fp1/P) - fI, (fp1/P) > or = fI where fo equals the fundamental frequency of the AC output voltage waveform, fp1 is inversely proportional to the conduction interval T1 and fI is the frequency of the AC input power source, second conduction control circuit means for generating a second conduction control signal to control the ON-OFF conduction controlled bilateral switching means associated with said second converter circuit, each of said bilateral switching means of said second converter circuit being rendered conductive by said conduction control signals for a period of time, T2, to develop a second output voltage waveform having the same fundamental frequency component as said first output voltage waveform and represented as fo fI - (fp2/P), (fp2P) > or = fI where fo equals the fundamental frequency of the AC output voltage waveform, fp2 is inversely proportional to the conduction interval T2 and fI is the frequency of the AC input power source, means for combining said first and second output voltage waveforms having essentially the same fundamental component to form said AC output voltage waveform across said load, said first conduction control signal comprised of pulses at a frequency corresponding to the value of fp1 and said second conduction control signal comprised of pulses at a frequency corresponding to the value of fp2, said first conduction control signal resulting in the reflection of the negative of the load phase angle back to the AC input power source, said second conduction control signal resulting in the reflection of the load phase angle unchanged back to the AC input power source, the combination of said output waveforms forming said AC output voltage resulting in a net zero input phase angle for said converter circuit means and consequently a unity input displacement factor.

Claim 6

An AC to AC frequency changer apparatus for developing an AC output voltage across a load, comprising, in combination, an AC input power source, a converter circuit means including a plurality of ON-OFF conduction controlled bi-lateral switching means forming a first and second converter circuit, each converter circuit having a pulse number P, wherein P represents the number of bi-lateral switching means employed in each converter circuit, said first and second converter circuits being operatively connected between said AC input power source and said load, each of said bi-lateral switching means being capable of conducting current in both directions between said input power source and said load, first conduction control circuit means for generating a first conduction control signal to control the ON-OFF conduction controlled bi-lateral switching means associated with said first converter circuit, each bi-lateral switching means of said first converter circuit being rendered conductive by said conduction control signals for a period of time, T1, to develop a first output voltage waveform having a fundamental frequency component represented as fo (fp1/P) - fI, (fp1/P) > or = fI where fo equals the fundamental frequency of the AC output voltage waveform, fp1 is inversely proportional to the conduction interval T1 and fI is the frequency of the AC input power source, second conduction control circuit means for generating a second conduction control signal to control the ON-OFF conduction controlled bilateral switching means associated with said second converter circuit, each of said bilateral switching means of said second converter circuit being rendered conductive by said conduction control signals for a period of time, T2, to develop a second output voltage waveform having the same fundamental frequency component as said first output voltage waveform and represented as fo fI - (fp2/P), (fp2P) > or = fI where fo equals the fundamental frequency of the AC output voltage waveform, fp2 is inversely proportional to the conduction interval T2 and fI is the frequency of the AC input power source, means for combining said first and second output voltage waveforms having essentially the same fundamental component to form said AC output voltage waveform across said load, said first conduction control signal comprised of pulses at a frequency corresponding to the value of fp1 and said second conduction control signal comprised of pulses at a frequency corresponding to the value of fp2, said first conduction control signal resulting in the reflection of the negative of the load phase angle back to the AC input power source, said second conduction control signal resulting in the reflection of the load phase angle unchanged back to the AC input power source, the combination of said output waveforms forming said AC output voltage resulting in a net zero input phase angle for said converter circuit means and consequently a unity input displacement factor.

Claim 7

An AC to AC frequency changer apparatus as claimed in claim 1 further including a clock pulse generator circuit means operatively connected to said first and second conduction controlleD circuit for supplying a first pulse train to control said first conduction control circuit and a second pulse train to control said second conduction control circuit, said clock post generator circuit means comprising, means for producing AC timing waves which are opposite in phase to the voltage waveforms of said AC input power source, a reference generator means for generating an AC reference waveform having a frequency substantially identical to the desired output frequency of said frequency changer apparatus, a first sine wave crossing detector circuit for generating first output pulses corresponding to the intersection of said AC reference waveform with the negative slopes of said timing waveforms, a second sine wave crossing detector circuit for producing second output pulses corresponding to the intersection of said AC reference waveform with the positive slopes of said timing waveforms, gating signal means operatively connected to said sine wave reference generator means and producing a first output which is phase shifted by +90* with respect to said sine wave reference waveform and a second output which is phase shifted by -90* with respect to said sine wave reference waveform, and logic means responsive to said output pulses of said first sine wave crossing detector circuit means, said output pulses of said second sine wave crossing detector circuit means, and said first and second output signals of said gating circuit means to produce a first pulse train (P1) for controlling the operation of said first conduction control circuit means in accordance with the following relationship: P1 S1 . X + S2 . X and a second pulse train (P2) for controlling the operation of said second conduction control circuit means in accordance with the following relationship:P2 S2 . X + S1 . X wherein; S1 represents the output pulses of said first sine wave crossing detector circuit means and S2 represents the output pulses of said second sine wave crossing detector circuit means, and x represents the output signal of said gating circuit means which is phase shifted by +90* with respect to said AC reference waveform, and X represents the output signal of said gating circuit means which is phase shifted by -90* with respect to said AC reference waveform.