NEMA Table
A
The inverse time algorithms will only work correctly if the proper Max Motor Inertia is used. If this
is known from the manufacturer, enter this value into parameter “Maximum Motor Inertia” (ID
1159).
If this value is zero, the NXGpro software will attempt to calculate the value based on the “Motor
kW Rating” (1010) and the synchronous speed (based on Motor Frequency (1020) and Full Load
Speed (1030)).
If the values are outside of the range of the NEMA Table 20-1 from NEMA Standard MG-1 in either
HP (kW) or Synchronous Speed, then the maximum value for the synchronous speed column
must be used.
The table below provides the NEMA table values in SI units, converted from lb-ft² to kg-m², for
easier application on the drive. Enter the result into the Maximum Motor Inertia parameter.
The table below was created by converting NEMA Table 20-1 values using the following
calculation:
Load Wk² = A * [Hp
0.95
/ (rpm/1000)
2.4
] - 0.0685 * [Hp
1.5
/ (rpm/1000)
1.8
]
Hp column and converting to kW by multiplying HP * 0.746
kW = 0.746 * Hp
Then converting the equivalent inertia from Wk² to SI by dividing lb-ft² by 23.73
1 kg-m² = 23.73 lb-ft² therefore:
J (kg-m²) = J (lb-ft²) / 23.73
Table A-1 NEMA Table 20-1 from NEMA Standard MG-1 1993 Part 20.42 converted to SI units, Maximum Load Inertia for
Polyphase Squirrel-Cage Induction Motors in kg-m²
Inertia from kW and speed in units of Kg-m² (23.73 lb-ft² = 1 kg-m²)
Hp kW 3600 1800 1200 900 720 600 514 450 400 360 327 300
100 75 533.9 709.2 914.5 1150.9 1419.7
125 93 657.8 874.4 1127.7 1419.3 1750.9
150 112 565.1 780.4 1037.1 1338.0 1683.9 2077.5
200 149 508.2 738.7 1020.6 1356.9 1750.5 2204.0 2718.1
250 187 401.6 624.9 908.6 1255.8 1670.5 2157.6 2713.9 3350.2
300 224 275.6 474.9 739.6 1075.9 1487.1 1978.9 2553.7 3219.6 3973.9
350 261 317.3 547.0 852.5 1240.2 1715.5 2284.0 2945.6 3712.6 4584.9
400 298 176.9 358.2 617.8 963.8 1402.4 1940.6 2583.2 3337.5 4205.6 5191.7
450 336 196.6 398.7 687.7 1073.3 1563.0 2161.8 2878.2 3721.0 4690.3 5790.1
500 373 216.2 438.3 756.8 1182.0 1721.4 2385.2 3173.2 4100.3 5166.5 6384.3
600 448 18.7 92.8 254.1 516.2 893.0 1395.3 2033.7 2815.0 3754.7 4850.4 6114.6 7555.8
700 522 21.2 105.9 290.8 592.5 1025.
7
1604.3 2338.8 3240.6 4323.6 5587.9 7045.9 8710.5
NXGPro+ Control Manual
Operating Manual, A5E50491925A 499
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