Marathon (Regal Rexnord)

BlackMax Inverter Duty

VSD screw compressor packages, inverter-driven fans.

Nameplate

Phase: 3-Phase
HP range: 1 – 500 HP
Voltage codes: 230/460 V · 460 V
NEMA frames: 143T – 449T
Enclosure: TEFC cast iron
Poles / RPM: 4, 6, 8
Efficiency: NEMA Premium
Insulation class: H (VPI'd) with corona-resistant magnet wire
Service factor: 1.15 (sine), 1.0 (VFD)
Family: BlackMax

Lead connection diagrams

9-lead Wye (High voltage · 460 V)

L1 ─┬─ T1 ── T7
L2 ─┬─ T2 ── T8
L3 ─┬─ T3 ── T9
     T4 ─┐
     T5 ─┼── tied together (neutral point)
     T6 ─┘

Tie T4-T5-T6 together and insulate. Feed line to T1/T2/T3; jumper T7-T1, T8-T2, T9-T3.

9-lead Delta (Low voltage · 230 V)

L1 ─┬─ T1 ── T6 ── T7
L2 ─┬─ T2 ── T4 ── T8
L3 ─┬─ T3 ── T5 ── T9

Parallel pairs: T1-T6-T7, T2-T4-T8, T3-T5-T9. No neutral tie.

Schematics & manuals

Marathon connection diagrams (SB761)

Links point to the manufacturer's own PDF hosting. If a link 404s, search the model number on the manufacturer's Download Center — filenames change with revision.

Field notes

1000:1 constant-torque turndown at inverter operation.
Grounding brush kit recommended above 100 HP on IGBT drives.

The connection charts above are the NEMA MG-1 industry-standard patterns most brands follow. Always confirm the exact chart printed inside your motor's peckerhead lid before landing leads — voltage-code and lead-tag conventions vary between OEMs and production years.

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