GE MM300 - Cooling Rate

CHAPTER 5: SETPOINTS PROTECTION ELEMENTS
MM300 MOTOR MANAGEMENT SYSTEM – INSTRUCTION MANUAL 5–39
The following tables illustrate the relation between GE Multilin MM2 and MM3 curve
numbers, NEMA curves, and the MM300 curve multipliers.
Table 5-2: MM2 and MM3 curve numbers and MM300 curve multipliers
Table 5-3: NEMA curves and MM300 curve multipliers
Cooling rate The model causes the thermal capacity used to decrease exponentially when the steady-
state thermal capacity used value is less than the actual thermal capacity used. This
simulates motor cooling. As a stopped motor normally cools significantly slower than a
running motor, the relay has two cooling time constant setpoints, one used when the
motor is off (stopped, tripped, locked out, pre-contactor, etc.), the other used when the
motor is on (starting, running, stopping). In each case, the time constant is time in minutes
for the motor temperature to cool by 63% of the difference between the initial
temperature and ambient temperature.
Figure 5-30: Thermal model cooling following a trip at t = 0
4.00 5.83 11.66 17.49 23.32 29.15 34.98 40.81 46.64 52.47 58.30 64.13 69.96 75.79 81.62 87.45
4.25 5.12 10.25 15.37 20.50 25.62 30.75 35.87 41.00 46.12 51.25 56.37 61.50 66.62 71.75 76.87
4.50 4.54 9.08 13.63 18.17 22.71 27.25 31.80 36.34 40.88 45.42 49.97 54.51 59.05 63.59 68.14
4.75 4.06 8.11 12.17 16.22 20.28 24.33 28.39 32.44 36.50 40.55 44.61 48.66 52.72 56.77 60.83
5.00 3.64 7.29 10.93 14.57 18.22 21.86 25.50 29.15 32.79 36.43 40.08 43.72 47.36 51.01 54.65
5.50 2.99 5.98 8.97 11.96 14.95 17.94 20.93 23.91 26.90 29.89 32.88 35.87 38.86 41.85 44.84
6.00 2.50 5.00 7.49 9.99 12.49 14.99 17.49 19.99 22.48 24.98 27.48 29.98 32.48 34.97 37.47
6.50 2.12 4.24 6.36 8.48 10.60 12.72 14.84 16.96 19.08 21.20 23.32 25.44 27.55 29.67 31.79
7.00 1.82 3.64 5.46 7.29 9.11 10.93 12.75 14.57 16.39 18.21 20.04 21.86 23.68 25.50 27.32
7.50 1.58 3.16 4.75 6.33 7.91 9.49 11.08 12.66 14.24 15.82 17.41 18.99 20.57 22.15 23.74
8.00 1.39 2.78 4.16 5.55 6.94 8.33 9.71 11.10 12.49 13.88 15.27 16.65 18.04 19.43 20.82
PICKUP
(× FLA)
STANDARD CURVE MULTIPLIERS
× 1 × 2 × 3 × 4 × 5 × 6 × 7 × 8 × 9 × 10 × 11 × 12 × 13 × 14 × 15
MM2 and MM3 curve number 1 2 3 4 5 6 7 8
MM300 curve multiplier 1 2 3 4 7 9 12 15
NEMA curve Class 10 Class 15 Class 20 Class 30
MM300 curve multiplier 4 6 8 12
0%
25%
50%
75%
100%
0 30 60 90 120 150 180
Time (minutes)
Cool time constant = 30 minutes
63%
Thermal capacity used
853732A1.CDR