The Delta DTR 007S21A is a single‑phase input, three‑phase output variable frequency drive (1 HP, 230 V/240 V) used in small industrial motor applications such as pumps and conveyors. Common failure modes for this model include overheating of the inverter bridge due to inadequate ventilation or overcurrent, failure of the main MOSFETs from voltage spikes, and degradation of the internal capacitors causing high ripple on the output. Initial diagnostics should verify that the input supply is within spec (230 V ±10 %) and that the drive’s built‑in temperature sensor reads normal; check for visible burn marks or swollen electrolytic caps on the PCB, then review any stored fault codes via the keypad or serial interface to pinpoint a specific component failure.[oss-gpt-20b]