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Differences between API 541, API 547, and IEEE 841, the US petrochemical industry motor standards
IEEE 841-2021: For ultra-high-efficiency, heavy-duty, fully enclosed, low-voltage squirrel-cage induction motors for the petrochemical industry, with a power range of 0.75 kW to 370 kW (1 hp to 500 hp).
API 541 and API 547: For high-voltage motors for the petrochemical industry. The specific differences between the two are as follows:
| Standard Features | API-541 4st Edition | AP1-547 1st Edition |
| Power | 500HP and above | 250HP to 3000HP |
| Frequency | 50Hz and 60Hz | 50Hz and 60Hz |
| Voltages | 2300V through 13,200V | 2300V through 13,200V (Dual voltage onlyfor 2300V/4000V) |
| Poles | 2 and higher | 4,6, and 8 (2 pole for 800HP and below intotally enclosed enclosure or 1250HP andbelow for WPll enclosures) |
| Available Starting methods | Direct on line (DOL) or Variable FrequencyDrive (VFD) | Direct on line (DOL) |
| Service Factor | 1 | 1 |
| Winding | Form Wound | Form Wound |
| Locked Rotor Current Limit | 650% | 650% |
| lEC and NEMA designs | Cast iron or fabricated steel frame materialdepending on frame size and enclosure se.lection | Cast iron or fabricated steel frame materialdepending on frame size and enclosureselection |
| Vibration | AP1-541 4th Edition vibration limits | AP1-547 1st Edition vibration limits |
| Noise levels | 85dB(A) at 1 m under no load | 85dB(A) at 1 m under no load |
| Enclosures | DPG, TEFC,WPI.WPII, TEAAC, and TEWAC | TEFC or WPII |
| Hazardous Area Classifications | Safe, Exn, Exp, or Exd | Exn or Exp |
| Insulation System | Sealed VPl insulation system | Sealed VPl insulation system |
| Protection Rating | IP-55 protection rating | IP-55 protection rating |
| Sleeve Bearings | Antifriction bearings available for smaller frame sizes and vertical motors; Provisions folBently Nevada series 3300 proximity probeson sleeve bearings | Antifriction bearings available for smallerframe sizes and vertical motors |
| Labyrinth Seals | Taconite labyrinth seals | Taconite labyrinth seals |
| Bearings | Both bearings insulated and a groundingstrap or brush on the DE | Both bearings insulated and agrounding strap or brush on the DE |
| Resistance TemperatureDevic (RTDs) | 2 per winding and 1 per bearing | 2 per winding and 1 per bearing |
| Space heater | Single voltage only for hazardous areas | Single voltage only for hazardous areas |
| Hardware | Stainless Steel | Stainless Steel |
| Rotor Core | C5 quality rotor core laminations | C5 quality rotor core laminations |
| Rotor | Copper Bar rotor | 1000HP and below = Die Cast Aluminum;above 1000HP=Copper Bar rotor |
| Air Filters | Air Filters for WPll enclosures | |
| Paint | WEG 212E paint plan for extremeconditions | WEG 212E paint plan for extremeconditions |
| Testing Included | Un-witnessed Routine APi-541 4th EditionTesting | Un-witnessed Routine API-547 1st EditionTesting |
