hereinafter , embodiments according to the present invention will be explained referring to the drawings . however , the present invention is not limited to examples of the following embodiments . fig1 shows a configuration of an electrical power control device to which the present invention is applied . a reference sign 1 denotes a direct - current power source ( dc power source ), for example , constituted by a circuit ranging from the point p ( to which the voltage vdc is applied ) to the battery 10 , i . e ., constituted by the battery 10 , the condensers c 1 and c 2 , the reactor l 1 , the switching elements 11 and 12 , and the free - wheel diodes 13 and 14 in fig3 . this direct - current power source 1 according to the present invention is not limited to the circuit shown by fig3 , and may be a direct - current power source having a thyristor - rectifier bridge circuit or a battery having the voltage value vdc . a reference sign 2 denotes a chopper circuit , for example , including the switching elements 15 and 16 , the free - wheel diodes 17 and 18 and the reactor l 2 in fig3 . a reference sign 3 denotes a control section including a function for calculating an electric power w . for example , this function of the control section 3 calculates the electric power w by using the above formulas ( 1 ) to ( 4 ) on the basis of the voltage vdc of point p of fig3 , the electric current idc flowing in the reactor l 2 , a switching duty d 1 of a first switching element ( the switching element 15 of fig3 ) of the chopper circuit 2 , a switching duty d 2 of a second switching element ( the switching element 16 of fig3 ) of the chopper circuit 2 , and the dead time dt between the first switching element and the second switching element . the switching duty d 1 satisfies a condition of 0 ≦ d 1 ≦ 1 . the switching duty d 2 satisfies a condition of 0 ≦ d 2 ≦ 1 . the dead time dt satisfies a condition of 0 ≦ dt ≦ 1 . moreover , the control section 3 includes a function for calculating an electric power w ′ adjusted by taking the equipment efficiency into consideration . this function of the control section 3 calculates the electric power w ′, by calculating an internal loss of the chopper circuit 2 and calculating the above formula ( 5 ) from the electric power w and a power ratio ( rate ) n of input and output of chopper circuit based on the internal loss . moreover , the control section 3 includes a function for performing a control for supplying direct - current power of the direct - current power source 1 to the direct - current load 4 and a ( regenerative ) control for returning direct - current power of the direct - current load 4 to the direct - current power source 1 by controlling the chopper circuit 2 . the direct - current load 4 , for example in fig3 , includes the inverter 19 for converting direct - current power into alternating - current power , and the pm motor 20 connected with an alternating - current side of the inverter 19 . the voltage vdc , the current idc , the switching duty ( duty time ) d 1 , the switching duty ( duty time ) d 2 and the dead time dt are known ( 1 = d 1 + d 2 + dt ) under the normal voltage control or current control . means for detecting these values are omitted from the depiction of fig1 . next , concrete examples will now be explained in each of which the present invention is applied to the motor drive device of fig3 . in the following examples , operations of the switching elements 11 , 12 , 15 and 16 at the time of drive mode of the pm motor 20 and at the time of regenerative mode of electric power of the pm motor 20 are basically as mentioned above . in a first example , the present invention is applied to a case where only the drive of the pm motor 20 is performed in the circuit of fig3 and where the switching duty d 1 of the switching element 15 is known . it is noted that the switching duty d 1 is represented by duty = a / b , wherein a denotes a turn - on time of the switching element and wherein b denotes one period of on - off operation . at this time , the switching elements 16 and 12 whose on - off controls are performed during the regenerative motion are unnecessary . hence , the combination of the switching element 16 and the diode 18 may be replaced with only the diode 18 , and the combination of the switching element 12 and the diode 14 may be replaced with only the diode 14 . a value of the current flowing in the point p (= the region to which the voltage vdc is applied ) of fig3 is equal to d 1 · idc . accordingly , the control section 3 of fig1 calculates the value of electric power w by the following formula ( 1 ). in a second example , the present invention is applied to a case where only the regeneration of electric power of the pm motor 20 ( regenerative mode by the pm motor 20 ) is performed in the circuit of fig3 and where the switching duty d 2 of the switching element 16 is known . at this time , the switching elements 15 and 11 whose on - off controls are performed during the drive motion are unnecessary . hence , the combination of the switching element 15 and the diode 17 may be replaced with only the diode 17 , and the combination of the switching element 11 and the diode 13 may be replaced with only the diode 13 . during the regeneration of electric power , a regeneration current flows through the switching element 15 or the diode 17 into the point p ( the region to which the voltage vdc is applied ) when the switching element 16 is in off state . accordingly , a value of this regeneration current is equal to a product ( multiplication ) of the current idc and a turn - off time ( 1 − d 2 ) of the switching element 16 . therefore , the control section 3 of fig1 calculates the value of electric power w by the following formula ( 2 ). in a third example , the present invention is applied to a case where the drive of the pm motor 20 is performed in the circuit of fig3 and where the switching duty d 2 of the switching element 16 is known . during the drive of the pm motor 20 , electric current flows from the point p when the switching element 15 is in on state . this turn - on time of the switching element 15 is represented by ( 1 − d 2 − dt ) using the turn - off time ( 1 − d 2 ) of the switching element 16 and the dead time dt . accordingly , a value of the current flowing in the point p is equal to ( 1 − d 2 − dt )· idc . therefore , the control section 3 of fig1 calculates the value of electric power w by the following formula ( 3 ). in a fourth example , the present invention is applied to a case where the regeneration of electric power of the pm motor 20 is performed in the circuit of fig3 and where the switching duty d 1 of the switching element 15 is known . during the electric - power regeneration , regenerative current flows in the point p through the switching element 15 turned on when the switching element 16 is in off state . this turn - off time of the switching element 16 is represented by a sum ( d 1 + dt ) of the switching duty d 1 of the switching element 15 and the dead time dt . accordingly , a value of the regenerative current flowing in the point p is equal to a product ( multiplication ) of the current idc and the turn - off time ( d 1 + dt ) of the switching element 16 . therefore , the control section 3 of fig1 calculates the value of electric power w by the following formula ( 4 ). in a fifth example , the present invention is applied to a case where the drive and the electric - power regeneration of the pm motor 20 are performed in the circuit of fig3 and where the switching duty d 1 of the switching element 15 and the switching duty d 2 of the switching element 16 are known . the control section 3 of fig1 calculates the value of electric power w by one of the above formulas ( 1 ) to ( 4 ) of the first to fourth examples . the value of electric power which is calculated in the first to fifth examples is the electric - power value of the point p ( the region to which the voltage vdc is applied ) of fig3 . hence , in a case of actual equipment ( device ), this electric - power value of the point p deviates from an electric - power value of input / output portion of the chopper circuit due to an internal loss . therefore , in this example , the internal loss is calculated . in the case that a rate of electric power of the input / output portion relative to the point p of fig3 is known as n , an accurate electric power w ′ of the input / output portion can be obtained by calculating the following formula ( 5 ) using the electric power w calculated in the first to fifth examples . it is noted that an efficiency η of the equipment can be used as this rate n . in a seventh example , a power control or power regulation ( apr ) including a control loop as shown in fig2 is applied to the switching elements 15 and 16 of fig3 which have performed the current control ( acr ) beforehand , on the basis of the electric - power value w ( w ′) calculated in the first to sixth examples . thereby , the power - running ( driving ) control and the power - regenerating control can be attained without providing additional current / voltage detector . fig2 extracts a part from fig3 , and shows components same as those of fig3 with same reference signs . in fig2 , a reference sign 30 denotes an electric - power control section for performing the power control ( apr ) on the basis of an electric - power command value w cmd and the electric - power value w ( w ′) calculated in the first to sixth examples . a reference sign 40 denotes an electric - current control section for performing the current control ( acr ) on the basis of an electric - current command value idc cmd and the electric - current detection value idc . an eighth example is done under the same case as the third example ( i . e ., under the case where the drive is performed in fig3 and where only the switching duty d 2 of the switching element 16 is known ) and also under the case of the seventh example . in the eighth example , the dead time dt of the above formula ( 3 ) is ignored . that is , the electric - power value w which is a control target is calculated by a following formula ( 6 ). in this case , an error in the control is caused by an influence of the dead time . therefore , the electric - power command value w cmd is modified into w ′ cmd as shown by a following formula ( 7 ). accordingly , the output electric - power control can be accurately performed because a correction depending on the dead time is added . a ninth example is done under the same case as the fourth example ( i . e ., under the case where the regeneration is performed in fig3 and where only the switching duty d 1 of the switching element 15 is known ) and also under the case of the seventh example . in the ninth example , the dead time dt of the above formula ( 4 ) is ignored . that is , the electric - power value w which is a control target is calculated by a following formula ( 8 ). in this case , an error in the control is caused by an influence of the dead time . therefore , the electric - power command value w cmd is modified into w ′ cmd as shown by a following formula ( 9 ). accordingly , the output electric - power control can be accurately performed because a correction depending on the dead time is added .