| Input voltage compatibility | Select a rated class matching the site supply: 200–240 V, 380–480 V, or 500–690 V AC; confirm single-phase or three-phase input. | Voltage mismatch can cause nuisance trips, reduced output power, or equipment damage. | Compare the nameplate voltage, allowable tolerance, phase arrangement, frequency, and short-circuit rating with the installation power system. |
| Motor and application rating | Size by motor current and load duty, not motor kW alone. Use normal-duty sizing for variable-torque loads and heavy-duty sizing for constant-torque loads. | Two motors with the same power rating may require different drive current capacity because of efficiency, power factor, altitude, and duty cycle. | Check motor full-load current, starting torque, load inertia, acceleration time, braking requirement, and operating speed range. |
| Overload capacity | A common benchmark is approximately 110% of rated current for 60 seconds in normal-duty operation and approximately 150% for 60 seconds in heavy-duty operation; actual values vary by model. | Adequate overload capacity supports conveyors, compressors, mixers, hoists, and other demanding loads. | Use the manufacturer’s published overload curve at the intended carrier frequency, ambient temperature, and altitude. |
| Control performance | For general machinery, sensorless vector control is typically sufficient. Closed-loop vector control is preferred where precise torque, speed regulation, or low-speed performance is required. | Control mode affects starting torque, speed accuracy, and stable operation under changing loads. | Review speed regulation, torque response, encoder compatibility, autotuning functions, and motor-cable limitations. |
| Frequency and speed range | Standard systems support 50/60 Hz supplies and adjustable output frequency. The usable motor speed range depends on motor cooling, torque profile, and control method. | Operating a standard motor continuously below its base speed may reduce self-cooling and require derating or forced ventilation. | Confirm minimum continuous speed, maximum frequency, constant-power range, and motor thermal protection method. |
| Energy-saving capability | For fans and pumps, variable-speed control can reduce throttling losses; energy results depend on the load profile, operating hours, and system curve. | The largest savings generally occur when flow or pressure can be reduced through speed control rather than mechanical throttling. | Estimate annual energy use from measured load points, operating hours, electricity tariffs, and expected speed reduction. |
| Input harmonics and power quality | Evaluate the drive’s input current distortion and consider line reactors, DC chokes, passive filters, or active front-end equipment where required. | Harmonics can affect transformers, capacitors, generators, protection devices, and sensitive control equipment. | Check compliance with the project’s power-quality limits and applicable requirements such as IEC 61000-3-12 or IEEE 519. |
| Environmental protection | Use an enclosure rating appropriate to the site, commonly IP20 for cabinet installation and higher IP ratings for exposed or dusty environments. Typical operating limits are around −10 to 50 °C before derating, depending on the design. | Dust, moisture, corrosive gas, vibration, altitude, and heat can shorten service life or reduce available output current. | Verify IP or NEMA rating, humidity limits, vibration rating, chemical exposure, altitude derating, cooling clearance, and cabinet ventilation. |
| Motor insulation and cable distance | Use inverter-duty motor insulation where possible. Long motor cables may require an output reactor, dV/dt filter, or sine-wave filter. | Fast switching edges can increase motor-terminal voltage stress, bearing currents, electromagnetic interference, and reflected-wave effects. | Check maximum cable length, switching frequency, grounding method, shield termination, and filter requirements in the installation manual. |
| Braking and regenerative energy | For frequent deceleration or overhauling loads, evaluate a braking resistor, braking unit, common DC bus, or regenerative front end. | Without a suitable energy path, DC-bus overvoltage may cause trips during stopping or load descent. | Calculate regenerated energy, braking power, duty cycle, resistor thermal capacity, and required stopping time. |
| Communication and integration | Prioritize the protocol used by the automation system, such as Modbus RTU, Ethernet-based industrial protocols, CANopen, or a fieldbus option. | Native compatibility reduces gateways, wiring, commissioning time, and potential communication faults. | Confirm supported protocols, data objects, baud rates, topology, cybersecurity controls, and PLC integration files. |
| Safety functions | A built-in Safe Torque Off function is a common baseline for machinery safety; additional functions may be required for speed or motion control. | Safety functions can reduce external components and help meet the machine risk assessment. | Verify the safety integrity level or performance level, dual-channel wiring, diagnostic coverage, and certification for the complete system. |
| International compliance | Confirm applicable market requirements, including CE, UKCA, UL/CSA, EMC, RoHS, and machine or electrical-equipment regulations. | Regulatory compatibility affects import clearance, installation approval, insurance, and customer acceptance. | Request current declarations, certificates, EMC category, installation conditions, and regional documentation before purchase. |
| Serviceability and lifecycle support | Prefer documented spare-part availability, parameter backup, removable control terminals, fault-history access, and regional technical support. | Downtime cost may exceed the initial purchase price, especially in continuous-process applications. | Compare warranty terms, repair locations, training, manuals, software access, lead time, and declared product lifecycle policy. |
| Total cost of ownership | Assess purchase price together with installation, filters, enclosure cooling, commissioning, energy use, maintenance, downtime, and disposal costs. | The lowest initial price is not necessarily the lowest lifetime cost. | Use a multi-year comparison based on operating hours, load profile, electricity price, service intervals, and expected failure impact. |
