APPLICATION NOTE
7
Ep2x p2x 0 VALUE = {V(on) * sin(A*V(shaft_angle) - (2-1)*(twopi/P))}
Ep3x p3x 0 VALUE = {V(on) * sin(A*V(shaft_angle) - (3-1)*(twopi/P))}
r1 p1x 0 1
r2 p2x 0 1
r3 p3x 0 1
S1p ppwr p1 p1x 0 switchp
S1n npwr p1 p1x 0 switchn
S2p ppwr p2 p2x 0 switchp
S2n npwr p2 p2x 0 switchn
S3p ppwr p3 p3x 0 switchp
S3n npwr p3 p3x 0 switchn
* 5v to drive, 0v to brake
Vppwr ppwr 0 PWL (0 5v .9 5v .901 0v 2s 0v)
Vnpwr npwr 0 PWL (0 -5v .9 -5v .901 0v 2s 0v)
* Clamping diodes to keep the kickback voltage down
D1p p1 ppwr dmod
D1n npwr p1 dmod
D2p p2 ppwr dmod
D2n npwr p2 dmod
D3p p3 ppwr dmod
D3n npwr p3 dmod
.model switchp vswitch (RON = .1 ROFF = 1e5 VON= .86 VOFF= .84)
.model switchn vswitch (RON = .1 ROFF = 1e5 VON=-.86 VOFF=-.84)
.model dmod D (RS = 10)
* "on" is used to enable the "brushes": 0 disconnects, 1 connects
* brushes to power.
Von on 0 PWL( 0,0 10ms,0 20ms,1 .8s,1 .81s,0 .9s,0 .91s,1)
ron on 0 1
.watch tran V([Shaft_Speed])
.tran 10ms 2s
.probe
.options acct
.end
Verifying Operation - Simulating the Model
Remember that simulating the motor takes lots of computer time (15 minutes on a 486-33 MHz PC), and
using the .PROBE command to save all the internal voltages and currents takes up lots of disk
space (2.5 Mb). The simulation run applies 5v to the motor brushes from 20ms to 0.8s. During this
time the motor accelerates to about 25rev/sec. Power is disconnected from 0.8s to 0.9s, and the motor
slows down due to friction losses. From 0.9s to the end of the simulation, the motor brushes are
connected to 0v making the motor slow quickly, as the back EMF provides reverse torque.
