Unlike vague guidelines, MG1-33 provides specific mitigation strategies. To be MG1-33 compliant, a motor in VFD service (especially over 100 HP or with high carrier frequencies) should include:
Motors do not fail from voltage or kVA directly; they fail from heat. Heat is proportional to current squared (I²R losses). MG1-33 defines how long a motor can safely operate at various load levels without exceeding its insulation temperature limits. nema mg1-32 amp- 33
Section 32 – Alternating Current Motors – Test Procedures for Polyphase Induction Motors
Section 33 – Temperature Tests (often referenced alongside 32 for full characterization) MG1-33 defines how long a motor can safely
These sections define the mandatory and preferred methods for determining performance, efficiency, and thermal limits of low- and medium-voltage polyphase induction motors (1 HP to thousands of HP). They are critical for motor manufacturers, repair shops, and end-users verifying compliance with NEMA design classes (A, B, C, D, E). When an induction motor starts, it draws a
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 starting kVA.
If this starting kVA is not correctly calculated: