If acceleration time exceeds 10 seconds, use a thermal overload relay with memory or a solid-state relay that models the I²t profile.
When an induction motor starts, it draws a high inrush current (typically 600% of full-load current) for a few cycles, followed by a starting current (typically 500–600% of full-load amps) until it reaches full speed. This current, multiplied by the voltage, gives the . nema mg1-32 amp- 33
– At extreme voltage/frequency limits, temperature rise may exceed MG1-32 limits. If acceleration time exceeds 10 seconds, use a
| Condition | Action per MG1-32/33 | |-----------|----------------------| | Altitude > 3300 ft | Reduce SF load or lower ambient | | Ambient > 40°C | Reduce load or use higher insulation class | | Voltage < -10% | May overheat at SF load – reduce load | | VFD operation | MG1-32/33 applies only at sinusoidal power – special VFD rules (MG1-31, MG1-40) | they are ensuring:
Engineers often overlook the massive inrush current required to start large induction motors (pumps, fans, compressors). MG 1-32 provides standardized methods for testing a generator's ability to start motors without excessive voltage dip. Tests such as the "Three-phase symmetrical short-circuit test" (32.13) and "Motor starting tests" (32.18) are referenced to ensure the exciter and voltage regulator can handle block loading.
When a generator manufacturer claims their genset complies with NEMA MG 1-33, they are ensuring: