Generic 3phase_power Error Code 3-Phase Voltage Imbalance

What does 3-Phase Voltage Imbalance mean?

Phase-to-phase voltages are not equal, causing motor overheating, increased current on worst phase, and equipment damage.

Common causes

• Unequal single-phase loads on phases (residential mixed with commercial)
• Open delta transformer connection
• Failing capacitor bank
• Blown fuse on one phase
• Failing utility feed

Diagnostic & testing steps

1. 1. Measure all 3 phase voltages: A-B, B-C, A-C
2. 2. Calculate average voltage
3. 3. Calculate imbalance: (Max deviation from avg / avg) × 100%
4. 4. NEMA limit: 1% voltage imbalance (causes ~6-8% current imbalance)
5. 5. Check fuses on all phases - blown fuse = single-phasing = immediate motor damage
6. 6. Measure each phase to neutral on 4-wire systems
7. 7. If utility feed issue, contact utility company

Tools required

• True RMS Multimeter
• Power quality analyzer
• Clamp meter

OEM parts & part numbers

Fuses, Power Quality Meter

Safety warning

⚠️ EQUIPMENT DAMAGE: 3-phase motor running on 2 phases (single-phasing) will overheat and fail within minutes. Shut down all motors immediately if single-phasing detected.