A brushless motor control system comprising: a three-phase brushless motor; and a brushless motor control device (10, 10a) configured to drive control the three-phase brushless motor, wherein the brushless motor control device (10, 10a) comprises: a phase voltage detector configured to detect a phase voltage of any one phase of three phases of the three-phase brushless motor; a zero-cross point detector configured to detect zero-cross points of the phase voltage of the one phase detected by the phase voltage detector; a zero-cross point estimator configured to measure a time interval T between the zero-cross points detected by the phase voltage detector, calculate a time T/3 and a time 2T/3 based on the time interval T between the zero-cross points, and estimate zero-cross points of two other phases of the three phases; and a conduction controller (22, 22a) configured to estimate a rotational position of a rotor based on the zero-cross points of the phase voltage of the one phase and the estimated zero-cross points of the two other phases, and control conduction on each phase coil of the three-phase brushless motor, wherein the brushless motor control system is characterized in that the three-phase brushless motor comprises a plurality of poles each including a U-phase coil, a V-phase coil, and a W-phase coil which are on a stator side, one of the U-phase coil, the V-phase coil, and the W-phase coil, which is included in one of the poles, is removed from other coils and thereby is floated, and the phase voltage detector is configured to detect a phase voltage of one of the three phases of the three-phase brushless motor using the floated coil. a three-phase brushless motor; and a brushless motor control device (10, 10a) configured to drive control the three-phase brushless motor, wherein the brushless motor control device (10, 10a) comprises: a phase voltage detector configured to detect a phase voltage of any one phase of three phases of the three-phase brushless motor; a zero-cross point detector configured to detect zero-cross points of the phase voltage of the one phase detected by the phase voltage detector; a zero-cross point estimator configured to measure a time interval T between the zero-cross points detected by the phase voltage detector, calculate a time T/3 and a time 2T/3 based on the time interval T between the zero-cross points, and estimate zero-cross points of two other phases of the three phases; and a conduction controller (22, 22a) configured to estimate a rotational position of a rotor based on the zero-cross points of the phase voltage of the one phase and the estimated zero-cross points of the two other phases, and control conduction on each phase coil of the three-phase brushless motor, wherein the brushless motor control system is characterized in that the three-phase brushless motor comprises a plurality of poles each including a U-phase coil, a V-phase coil, and a W-phase coil which are on a stator side, one of the U-phase coil, the V-phase coil, and the W-phase coil, which is included in one of the poles, is removed from other coils and thereby is floated, and the phase voltage detector is configured to detect a phase voltage of one of the three phases of the three-phase brushless motor using the floated coil. a phase voltage detector configured to detect a phase voltage of any one phase of three phases of the three-phase brushless motor; a zero-cross point detector configured to detect zero-cross points of the phase voltage of the one phase detected by the phase voltage detector; a zero-cross point estimator configured to measure a time interval T between the zero-cross points detected by the phase voltage detector, calculate a time T/3 and a time 2T/3 based on the time interval T between the zero-cross points, and estimate zero-cross points of two other phases of the three phases; and a conduction controller (22, 22a) configured to estimate a rotational position of a rotor based on the zero-cross points of the phase voltage of the one phase and the estimated zero-cross points of the two other phases, and control conduction on each phase coil of the three-phase brushless motor, wherein the brushless motor control system is characterized in that the three-phase brushless motor comprises a plurality of poles each including a U-phase coil, a V-phase coil, and a W-phase coil which are on a stator side, one of the U-phase coil, the V-phase coil, and the W-phase coil, which is included in one of the poles, is removed from other coils and thereby is floated, and the phase voltage detector is configured to detect a phase voltage of one of the three phases of the three-phase brushless motor using the floated coil.