直流(liu)電(dian)(dian)(dian)(dian)機(ji)(ji)(ji)(ji)（direct current machine）是(shi)指能(neng)將(jiang)直流(liu)電(dian)(dian)(dian)(dian)能(neng)轉(zhuan)(zhuan)(zhuan)換(huan)成(cheng)機(ji)(ji)(ji)(ji)械(xie)能(neng)（直流(liu)電(dian)(dian)(dian)(dian)動(dong)機(ji)(ji)(ji)(ji)）或(huo)將(jiang)機(ji)(ji)(ji)(ji)械(xie)能(neng)轉(zhuan)(zhuan)(zhuan)換(huan)成(cheng)直流(liu)電(dian)(dian)(dian)(dian)能(neng)（直流(liu)發電(dian)(dian)(dian)(dian)機(ji)(ji)(ji)(ji)）的(de)旋(xuan)轉(zhuan)(zhuan)(zhuan)電(dian)(dian)(dian)(dian)機(ji)(ji)(ji)(ji)。它是(shi)能(neng)實(shi)現直流(liu)電(dian)(dian)(dian)(dian)能(neng)和機(ji)(ji)(ji)(ji)械(xie)能(neng)互相轉(zhuan)(zhuan)(zhuan)換(huan)的(de)電(dian)(dian)(dian)(dian)機(ji)(ji)(ji)(ji)。當它作(zuo)電(dian)(dian)(dian)(dian)動(dong)機(ji)(ji)(ji)(ji)運行時是(shi)直流(liu)電(dian)(dian)(dian)(dian)動(dong)機(ji)(ji)(ji)(ji)，將(jiang)電(dian)(dian)(dian)(dian)能(neng)轉(zhuan)(zhuan)(zhuan)換(huan)為(wei)機(ji)(ji)(ji)(ji)械(xie)能(neng)；作(zuo)發電(dian)(dian)(dian)(dian)機(ji)(ji)(ji)(ji)運行時是(shi)直流(liu)發電(dian)(dian)(dian)(dian)機(ji)(ji)(ji)(ji)，將(jiang)機(ji)(ji)(ji)(ji)械(xie)能(neng)轉(zhuan)(zhuan)(zhuan)換(huan)為(wei)電(dian)(dian)(dian)(dian)能(neng)。