QN 1
(a) A DC motor drive is fed from a 1-quadrant chopper with a source voltage of
360 V DC and at a frequency of 10 kHz. on-state voltage drop across the
controlled switch and diode are respectively, 2.5 V and 1.5 V, regardless of
current variation. Motor parameters and ratings are as follows: 260 V, 1785
rpm, 7.5 kW, Ra=0.5, La=2 mH, Bfri=0.007 Nm-s/rad and J=0.035 kg-m2.
Consider the motor to operate at 70% rated load at 25% rated speed.
(i) Sketch the armature voltage and current waveforms indicating magnitudes
and graduating the time axis
o The rated armature current is obtained as
Pag 7744.6W
I a , rated 31.722 A
Te, rated 41.432 Nm
TL , rated 40.124 Nm
kt 1.3061Nm / A
ke 1.3061V / rad / s
Te, new 28.414 Nm
I a , new 21.755 A
(a) A DC motor drive is fed from a 1-quadrant chopper with a source voltage of
360 V DC and at a frequency of 10 kHz. on-state voltage drop across the
controlled switch and diode are respectively, 2.5 V and 1.5 V, regardless of
current variation. Motor parameters and ratings are as follows: 260 V, 1785
rpm, 7.5 kW, Ra=0.5, La=2 mH, Bfri=0.007 Nm-s/rad and J=0.035 kg-m2.
Consider the motor to operate at 70% rated load at 25% rated speed.
(i) Sketch the armature voltage and current waveforms indicating magnitudes
and graduating the time axis
o The rated armature current is obtained as
Pag 7744.6W
I a , rated 31.722 A
Te, rated 41.432 Nm
TL , rated 40.124 Nm
kt 1.3061Nm / A
ke 1.3061V / rad / s
Te, new 28.414 Nm
I a , new 21.755 A
