Apparatus for controlling driving of reciprocating compressor and method thereof

An apparatus for controlling a driving of a reciprocating compressor, comprising:

• a controlling unit which judges a load size by comparing a phase difference between a current and a stroke with a reference phase difference, and outputting a frequency control signal and a stroke control signal according to the judgment result;
• a driving frequency command value determining unit which determines a driving frequency command value according to the frequency control signal;
• a stroke command value determining unit which determines a stoke command value according to the stroke control signal;
• a first comparing unit which compares the driving frequency command value with a current driving frequency, the first comparing unit outputting a frequency compensation signal according to the comparison result;
• a second comparing unit which compares the stroke command value with a current stroke, the second comparing unit outputting a stroke compensation signal according to the comparison result;
• a PWM controlling unit which outputs a PWM control signal to vary a driving frequency and a stroke according to the frequency compensation signal and the stroke compensation signal;
• and
• an inverter which varies a voltage and a driving frequency applied to
• a motor according to the PWM control signal.

A method for controlling a driving of a reciprocating compressor, comprising:

• driving a reciprocating compressor with a capacity corresponding to a certain stroke command value;
• detecting a current and a voltage applied to a motor of the reciprocating compressor, and calculating a stroke by the detected current and voltage;
• detecting a phase difference between the calculated stroke and the detected current;
• and
• comparing the detected phase difference with a reference phase difference, and varying a stroke command value and a driving frequency command value according to the comparison result,
• wherein the varying a stroke command value and the driving frequency command value, when the detected phase difference between the current and the stroke is less than the reference phase difference, comprises varying a current driving frequency into a driving frequency larger than a resonance frequency.

A method for controlling a driving of a reciprocating compressor, comprising:

• driving a reciprocating compressor with a capacity corresponding to a certain stroke command value;
• detecting a current and a voltage applied to a motor of the reciprocating compressor, and calculating a stroke by the detected current and voltage;
• detecting a phase difference between the calculated stroke and the current;
• comparing the detected phase difference with a reference phase difference, and varying a stroke command value and a driving frequency command value according to the comparison result;
• comparing the varied driving frequency command value with a current driving frequency, and generating a frequency compensation signal according to the comparison result;
• comparing the varied stroke command value with a current command value, and generating a stroke compensation signal according to the comparison result;
• generating a PWM control signal to vary a stroke voltage and a driving frequency according to the frequency compensation signal and the stroke compensation signal;
• and
• varying a stroke voltage and a driving frequency applied to a motor of the reciprocating compressor according to the PWM control signal.