NEMA voltage unbalance calculator. Enter the measured Line-Line voltage to quickly calculate the % voltage unbalance based on NEMA Equation.Essential for electrical engineers, maintenance teams, and HVAC technicians to detect harmful voltage unbalance that can damage motors, reduce efficiency, and cause overheating.
Voltage unbalance occurs when the voltages in a three-phase system are not equal in magnitude or have phase displacement issues. This can cause increased motor heating, reduced efficiency, and premature failure.
Measure the three phase-to-phase voltages, find the average, determine the maximum deviation from that average, and divide it by the average voltage, then multiply by 100. Our calculator does this instantly for you.
According to NEMA MG1, voltage unbalance should not exceed 1% for continuous motor operation. Higher unbalance can reduce motor life significantly.
Even a 1% voltage unbalance can cause 6–10% current unbalance, leading to overheating, insulation damage, vibration, and reduced efficiency.
No, voltage unbalance is a three-phase power quality issue. This tool is designed for three-phase voltage measurements.
Common causes include uneven distribution of single-phase loads, faulty connections, blown fuses on one phase, or utility supply issues.
Yes, the calculation method is frequency-independent and works for both 50 Hz and 60 Hz three-phase systems.
It’s best to measure steady-state running voltages for accurate results. Startup conditions may cause temporary voltage drops that do not reflect system balance.
No, all voltage inputs are processed in your browser and are not stored on our servers.
Investigate load distribution, check supply connections, balance single-phase loads, and contact your utility provider if the issue originates from the supply side.