DIA GNOSTICS 129
7.3.4 FLD I LOOP M ONITOR / Field firing angle of advance monitor PIN 146
Note this parameter is only updated if the field is enabled. The convention used is 0 degrees is
no firing and 180 degrees is full firing. The formula for calculating the field volts is as follow s
Volts = 0.45 * A C supply volts *(1-cos alpha). (Firing angle of advance (degrees) = alpha)
Field volts table. Note. The result is rounded do wn then reduced by 1 volt due to the drop in the field bridge.
Firing angle (deg) AC supply 200 AC supply 240 AC supply 380 AC supply 415 AC supply 480
25
Minimum field Minimum field Minimum field Minimum field Minimum field
30
12 14 22 24 28
40
20 24 39 42 49
50
31 37 60 65 76
60
44 53 84 92 107
70
58 70 111 121 141
80
73 88 140 154 177
90
89 107 170 185 215
100
104 125 199 218 252
110
119 143 228 249 288
120
134 161 255 279 324
130
146 176 279 305 353
140
157 189 300 328 380
150
166 200 318 347 402
160
173 208 330 361 416
170
177 213 338 369 427
177
179 215 341 372 430
After about 150 degrees there is only about 5 % more volts available. This is important to realise when
operating in the current control mode. In order to maintain the correct current, the volts must be able to
move higher as the field w arms up and the field winding resistance increases. Also it is necessary to allow a
margin for supply tolerance.
This means that w hen the field is at its highest operating temperature the firing angle should not normally
exceed 1 50 degrees to be sure of preventing saturation of the control loop. A typical field winding resistance
will change by about 20% bet w een cold and running temperature. Hence the maximum cold firing angle wi ll
be at about 1 25 degrees. If the field loop does saturate, then the speed loop will have to work harder to
maintain control. In A VF (Armature voltage feedback) systems the speed holding may be less accurate.
7.3.5 FLD I LOOP MO NIT OR / Field active monitor PIN 147
FLD I LOOP MO NITOR 3
146)A NGLE OF A DV A NCE
146)A NGLE OF A DV A NCE
0 DEG
PARA METER RANGE PIN
ANGLE OF A DV A NCE 0 to 180 DEG 146
Shows the value of the field bridge firing
angle of advance in degrees.
FLD I LOOP MO NITOR 3
147)FIELD A CTIVE MON
147)FIELD A CTIVE MON
DISABLED
PARA METER RANGE PIN
FIELD ACTIVE M ON ENABLED OR DIS ABLED 147
Shows whether the field output is active
(ENABLED) or inactive (DISABLED).
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