EPH (EPH1, EPH0) Input Phase Failure fault in Toshiba drive
EPH (EPH1, EPH0) Input Phase Failure fault in Toshiba drive
Description EPH indicates that one of the three input power phases (R, S, T / L1, L2, L3) is missing or has a significant voltage imbalance. The drive monitors the ripple on the DC bus. If a phase is lost, the DC bus ripple increases drastically. Running on a single phase puts extreme stress on the input rectifier bridge and capacitors, so the drive trips to prevent hardware explosion. Causes
1. Blown Fuse: A fuse on the main distribution panel or disconnect switch has blown on one phase.
2. Loose Connection: A wire is loose at the input terminal block of the drive or the breaker.
3. Contact Failure: A magnetic contactor feeding the drive has pitted or burnt contacts that aren't conducting on one pole.
4. Grid Failure: The utility company has dropped a phase (common in rural areas or during storms). Solution This is purely an input power problem. Get your multimeter and measure AC voltage at the drive input terminals (L1 to L2, L2 to L3, L3 to L1). All three readings should be balanced (e.g., all 480V or all 230V). If you measure 480V, 480V, and 0V (or weird phantom voltage like 120V), you have lost a phase.
Trace the power back. Check the fuses in your disconnect box—checking voltage *across* a fuse is a good trick (if you read voltage across a fuse, that fuse is blown). Check the contactor feeding the drive; often the coil pulls in, but the physical copper contacts inside are burnt away.
Tighten all screw terminals. Thermal cycling causes copper wires to shrink and expand, loosening screws over time. If the input voltage is perfectly balanced but the drive still trips EPH, the internal input detection circuit of the VFD may be damaged. Note: If you are intentionally running a 3-phase drive on single-phase power (which requires significant derating), you must navigate to the "Input Phase Failure Detection" parameter and turn it OFF to prevent nuisance tripping.
Description EPH indicates that one of the three input power phases (R, S, T / L1, L2, L3) is missing or has a significant voltage imbalance. The drive monitors the ripple on the DC bus. If a phase is lost, the DC bus ripple increases drastically. Running on a single phase puts extreme stress on the input rectifier bridge and capacitors, so the drive trips to prevent hardware explosion. Causes
1. Blown Fuse: A fuse on the main distribution panel or disconnect switch has blown on one phase.
2. Loose Connection: A wire is loose at the input terminal block of the drive or the breaker.
3. Contact Failure: A magnetic contactor feeding the drive has pitted or burnt contacts that aren't conducting on one pole.
4. Grid Failure: The utility company has dropped a phase (common in rural areas or during storms). Solution This is purely an input power problem. Get your multimeter and measure AC voltage at the drive input terminals (L1 to L2, L2 to L3, L3 to L1). All three readings should be balanced (e.g., all 480V or all 230V). If you measure 480V, 480V, and 0V (or weird phantom voltage like 120V), you have lost a phase.
Trace the power back. Check the fuses in your disconnect box—checking voltage *across* a fuse is a good trick (if you read voltage across a fuse, that fuse is blown). Check the contactor feeding the drive; often the coil pulls in, but the physical copper contacts inside are burnt away.
Tighten all screw terminals. Thermal cycling causes copper wires to shrink and expand, loosening screws over time. If the input voltage is perfectly balanced but the drive still trips EPH, the internal input detection circuit of the VFD may be damaged. Note: If you are intentionally running a 3-phase drive on single-phase power (which requires significant derating), you must navigate to the "Input Phase Failure Detection" parameter and turn it OFF to prevent nuisance tripping.
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