Table of Contents
Advertisement
5 SETPOINTS
HIGH FIELD:
ENTER to modify
HI EXC FLD:
ENTER to modify
FUNCTION:
The calculation of field (exciter) voltage divided by field (exciter) current yields field ohms. Tripping action is ini-
tiated if the calculated resistance exceeds the HIGH FIELD (HI EXC FLD) setpoint, indicating a field overtempera-
ture condition. A separate accessory package (PG2SPM or PG4SPM) is required to utilize this feature.
Table 5–2: FIELD OVERTEMPERATURE RANGE / STEP VALUES
DC CT PRIM
SETPOINT
MINIMUM
5 to 19 A
20 to 200 A
201 to 1000 A
MOTOR TYPE:
Collector-Ring or Brushless
APPLICATION:
This function emulates a resistance temperature detector (RTD) on the field windings. The resistance of an
RTD is temperature dependent – it increases as the temperature increases. In this case, the RTD behavior is
emulated by examining the field voltage and current. As the ratio of field voltage to field current increases, the
field resistance increases, indicating an increase in temperature of the field windings.
The motor nameplate contains the motor's maximum temperature rise and field resistance. This information is
used with the multiplier from the table below to determine the maximum field ohms, and therefore the maxi-
mum field winding temperature, at which the motor should be allowed to operate.
Table 5–3: FIELD OHMS MULTIPLIER
RISE °C
MULTIPLIER
0
1.0
5
1.02
10
1.04
15
1.06
20
1.08
25
1.10
30
1.12
EXAMPLE:
A motor with a nameplate field resistance of 2 Ω at 25°C with insulated copper windings has a maximum tem-
perature rise of 80°C. This corresponds to a field resistance of 1.31 times the resistance at 25°C. So, the FIELD
OHMS setpoint is set to 1.31 × 2 Ω = 2.62 Ω.
GE Multilin
Courtesy of store.ips.us
5.2.14 FIELD OVERTEMPERATURE (HIGH FIELD OHMS) PROTECTION
OFF
Collector-Ring:
OFF
Brushless:
HIGH FIELD/HIGH EXC FLD
MAXIMUM
10 Ω
450 Ω
1 Ω
40 Ω
0.20 Ω
5 Ω
RISE °C
40
50
60
70
80
90
100
SPM Synchronous Motor Protection and Control
Range: see below
Step: see below
Range: see below
Step: see below
FIELD OHMS
VALUE
< 1 Ω
< 10 Ω
< 450 Ω
MULTIPLIER
RISE °C
1.15
110
1.19
120
1.23
130
1.27
140
1.31
150
1.35
160
1.39
170
5.2 SETPOINTS MENU
STEP
0.01 Ω
0.1 Ω
1 Ω
MULTIPLIER
1.42
1.46
1.50
1.54
1.57
1.60
1.64
5
5-
7
Advertisement
Table of Contents
