Uninterruptible power supplies

An uninterruptible power supply comprising,

• a voltage regulating transformer, first input means for coupling a primary AC voltage to the transformer, second input means for coupling a DC voltage energized inverter circuit to the transformer and output means for accepting a load to be energized,
• the first input means for coupling including means for disconnecting the primary AC voltage and
• stored program control means having memory means including instruction routines for controlling said means for disconnecting in response to signal conditions of the primary AC voltage,
• a first counter preset with a numerical value to be counted down to establish a timed interval longer than a half period of the primary AC signal,
• a first instruction routine for measuring the half period of the primary AC voltage signal by evaluating a count value remaining in the counter at the expiration of the period of the primary AC signal, and further utilizing the count value remaining to establish the actual frequency of the primary AC signal and acting to disable the means for connecting if the frequency is deemed to be unacceptable, and
• a second instruction routine responsive to the count value remaining in the first counter and operative for computing a numerical value entered into a second counter for generating a comb pulse waveform so that positioning of the individual pulses occur at precise degree locations of the primary AC voltage signal, and
• said memory means including a third instruction routine responsive to pulses of the comb pulse waveform and operative for sampling an amplitude of the primary AC voltage signal, and means for enabling the means for connecting if the amplitude is unacceptable.

An uninterruptible power supply comprising;

• a regulating transformer having a first input coupled to accept a primary AC voltage source, a second input coupled to accept a reserve AC voltage source and an output means for accepting a load, power flow control means for selectively controlling power flow from the primary and reserve AC voltage sources to the output means by adjusting a phase of a voltage of the reserve source relative to a phase of the voltage of the primary source, the power flow control means comprising a central processor means, memory means, a counter and signal sensing means to couple information about the primary AC signal to the central processor,
• the memory means including a first instruction routine to preset the counter with a number and the central processing means supplying clock signals to count down the number, the number preset in the counter being selected so that a count down interval exceeds a half period of the primary AC voltage at its desired frequency, the signal sensing means coupled to respond to a first zero crossing of the primary AC voltage and initiate count down in the counter, a second instruction routine responsive through the signal sensing means to a second zero crossing of the primary AC voltage subsequent to the first zero crossing and operative to store a count remainder existing momentarily uncounted in the counter and further operative to compare the count remainder with a table of count values in the memory means to determine if a frequency of the primary AC voltage is acceptable and disconnect means for disabling the first input in response to the second instruction routine of the frequency of the primary AC voltage is unacceptable,
• said power flow control means further including instructions in the second instruction routine for generating a comb pulse waveform and a third instruction routine operative for activating the sensing means for measuring an amplitude value of the primary AC voltage in response to individual teeth pulses of the comb waveform, and the third instruction routine comparing the amplitude value with a proper amplitude value for each individual tooth pulse in the memory means.

An uninterruptible power supply comprising

• a regulating transformer including output means for connection to a load,
• first input means for coupling a primary AC voltage to the regulating transformer,
• second input means for coupling a reserve AC voltage to the regulating transformer,
• signal amplitude monitoring means coupled to the first input means for sampling an amplitude of the primary AC voltage at predetermined angles of the primary AC voltage, and comprising
• signal generation means for generating a comb waveform having individual pulses coincident with a plurality of preselected angles within each half cycle of the primary AC voltage, and signal sensing means responsive to the individual pulses for measuring an instantaneous amplitude of the primary AC voltage, and control means responsive to the signal sensing means for disabling the first input means if at least two successive instantaneous amplitudes within one half-cycle of the primary AC voltage deviate from a desired value.

An uninterruptible power supply comprising

• a regulating transformer having first and second inputs and an output,
• means for evaluating acceptability of an AC voltage at the first input means comprising
• means for sampling a plurality of amplitudes within each half-cycle of the AC voltage at a plurality of precise angles relative to a zero crossing of the AC voltage,
• said means for sampling including means for designating individual sampling intervals at the precise angles of the AC voltage by generating a plurality of timing pulses,
• means for evaluating at least two successive ones of the plurality of amplitudes sensed by the means for sampling in order to determine acceptability of the AC voltage, and
• means for disabling the first input if the means for evaluating determines the AC voltage to be unacceptable.

An uninterruptible power supply comprising;

• a regulating transformer including first and second input windings and an output winding,
• a line switch for coupling a primary AC voltage source to the first input winding,
• an inverter circuit adapted to be energized by a reserve DC voltage source and having power switches coupled to supply AC voltage to the second input winding,
• control means operative for controlling a phase of a signal generated by the inverter circuit relative to the primary AC voltage comprising
• a microprocessor, a memory, a first and second counter, a priority interrupt, an A/D signal sensing circuit, and a control signal circuit all coupled to the microprocessor by a common bus,
• a first sensing circuit coupled for sensing zero crossings and a second sensing circuit for sensing a signal amplitude of the primary AC voltage,
• a driving circuit for driving switch devices of the inverter circuit in response to commands of the microprocessor,
• said memory including a first instruction to preset the first counter with a number that is counted down at a preset frequency with a count down interval exceeding a period of a normal primary AC voltage, a second instruction responding to a zero crossing detected by the first sensing circuit and operative for reading a number value existing within the first counter which has not yet been counted down, a third instruction utilizing the number value existing for computing a number entered into the second counter to generate a comb waveform whereby comb pulses appear at preselected angles of the primary AC voltage, a fourth instruction responsive to comb pulses and operative for reading voltage amplitude samples detected by the second sensing circuit and comparing this to reference values stored in memory, said control means operative for disabling the line switch if the voltage amplitude samples are deemed unacceptable.

An uninterruptible power supply comprising

• a regulating transformer including output means for connection to a load,
• first input means for coupling a primary AC voltage to the regulating transformer,
• second input means for coupling a reserve AC voltage to the regulating transformer,
• signal amplitude monitoring means coupled to the first input means for sampling amplitude of the primary AC voltage at predetermined angles of the primary AC voltage, and comprising
• signal generation means for generating a comb waveform having individual pulses coincident with preselected angles of the primary AC voltage,
• said signal generation means including means for comparing an actual period of the primary AC voltage to a reference interval and means responsive to the means for comparing for utilizing a time difference of the period and the interval to compute timing of pulses of the comb waveform,
• and signal sensing means responsive to the individual pulses for measuring an instantaneous amplitude of the primary AC voltage, and control means responsive to the signal sensing means for disabling the first input means if instantaneous amplitudes of the primary AC voltage deviate from a desired value.