GE M60 UR Series, Instruction Manual

Page: 284 / 662

5-156 M60 Motor Protection System GE Multilin
5.6 GROUPED ELEMENTS 5 SETTINGS
5
• VD STALL CURRENT @ 100% V : This setting defines the locked rotor current level at the rated motor voltage ( I
3
).
• VD SAFE STALL TIME @ 100% V : This setting defines the maximum time the motor is allowed to withstand the
locked rotor current at rated motor voltage ( t
3
).
• VD ACCEL. INTERESECT @ 100% V : This setting defines the starting current level corresponding to the crossing
point between the acceleration thermal limit at rated voltage and the programmed relay overload curve ( I
4
). This value
can be typically determined from the motor acceleration curves. The current value at the breakdown torque for the
100% voltage start is recommended for this setting.
The voltage dependent overload curves are shown below.
Figure 5–62: VOLTAGE DEPENDENT OVERLOAD CURVES
1.00
10.00
100.00
1000.00
10000.00
0 1 2 3 4 5 6 7 8
PER UNIT CURRENT
TIME
T
O
TR
IP
(SEC
ON
D
S
)
THERMAL MODEL CUR V E LOCKED ROTOR LINE MIN V ACCELERATE
100% ACCELERATE 110% ACCELERATE MIN V LINE
100% V LINE 110% V LINE
THERMAL MODEL CURVE
ACCELERATION INTERSECT@ minV (2)
ACCELERATION INTERSECT@ 100%V (4)
ACCELERATION INTERSECT@ 110%V (6)
SAFE STALL POINT @ minV (1)
SAFE STALL POINT @ 100%V (3)
SAFE STALL POINT @ 110%V (5)
LOCKED ROTOR THERMAL LIMIT CURVE
THERMAL LIMIT CURVES
FOR ABNORMAL CONDITIONS:
- LESS THAN Vmin (A)
- MORE THAN 110%V (B)
- LOSS OF VOLTAGE (C)
A
B
C
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