| Rated Voltage | Common system classes include 2.3 kV, 3.3 kV, 4.16 kV, 6.0 kV, 6.6 kV and 6.9 kV; higher project-specific ratings may also be available. | The drive must match the motor insulation system, plant distribution voltage and insulation coordination requirements. | Confirm nominal voltage, allowable voltage tolerance, frequency, short-circuit level and grounding arrangement. | Critical |
| Power Rating | Typically used for medium- and high-power motors from several hundred kilowatts to multiple megawatts. | Correct sizing prevents overheating, nuisance trips and inefficient operation under the actual load profile. | Size against motor current, service factor, altitude, ambient temperature, overload duty and starting frequency rather than motor kW alone. | Critical |
| Topology | Common architectures include multilevel voltage-source inverters, cascaded H-bridge designs and load-commutated inverters for suitable applications. | Topology influences output waveform quality, component redundancy, maintenance strategy, motor compatibility and footprint. | Request the single-line diagram, cell or power-module arrangement, bypass method and fault-containment approach. | Critical |
| Motor Compatibility | Usually suitable for medium-voltage induction motors; synchronous motor compatibility depends on the drive design and excitation system. | A drive can require specific motor insulation, bearing protection, cable length or minimum pulse-width-modulation conditions. | Verify motor data sheet, insulation class, rotor type, cable length, bearing arrangement and allowable dv/dt. | Critical |
| Speed Control Range | Application-dependent; open-loop control commonly provides a broad operating range, while closed-loop control is used when high low-speed torque or speed accuracy is required. | Pumps, fans, compressors, conveyors and mills have different torque and speed-control requirements. | Define minimum operating speed, speed accuracy, acceleration time, reversing needs and low-speed cooling requirements. | High |
| Overload Capability | Often specified as a short-duration current or torque overload, with the actual value and duration varying by model and duty class. | High-inertia loads and constant-torque applications may need significantly more starting and transient capacity than variable-torque loads. | Compare continuous current, overload percentage, overload duration, repetition interval and thermal recovery model. | Critical |
| Input Power Factor | Depends on the front-end design and load point; active front ends can provide near-unity displacement power factor under suitable conditions. | A higher power factor reduces reactive-power demand and can improve transformer and upstream feeder utilization. | Request displacement power factor and true power factor at 25%, 50%, 75% and 100% load. | High |
| Input Harmonic Distortion | Performance varies widely with the rectifier, phase-shifting transformer, passive filters or active front end; compliance is project-specific. | Harmonics can cause transformer heating, capacitor stress, interference and voltage distortion in the plant network. | Require a harmonic study based on the complete electrical system and identify the applicable IEEE 519 or local limits. | Critical |
| Output Waveform and Motor Stress | Multilevel output stages can reduce voltage steps and motor insulation stress compared with basic two-level switching. | Lower dv/dt and reduced common-mode effects can support longer motor-cable runs and help manage bearing-current risks. | Check measured output voltage quality, dv/dt, common-mode voltage, reflected-wave risk and cable-length limits. | Critical |
| Efficiency | Complete drive efficiency depends on topology, switching frequency, transformer losses, auxiliary systems and operating load. | Small efficiency differences can create substantial annual energy and cooling costs in continuous-duty installations. | Compare guaranteed total efficiency at the actual operating points, including input transformer and cooling equipment where applicable. | High |
| Regenerative Braking | Available only with a suitable regenerative front end or braking system; standard diode-front-end drives generally require an alternative energy-management method. | Regeneration is valuable for descending conveyors, centrifuges, test stands and other applications with frequent deceleration. | Calculate braking power, regenerated energy, duty cycle, grid acceptance and dynamic braking requirements. | Application-specific |
| Ride-Through and Restart | Functions may include undervoltage ride-through, flying restart, controlled ramp recovery and automatic restart after an approved fault condition. | Process continuity is important for fans, pumps, compressors and conveyors where an unexpected stop can damage equipment or interrupt production. | Define voltage sag profile, restart permissives, coast-down behavior, process interlocks and safety requirements. | High |
| Cooling Method | Air-cooled systems are common; liquid cooling may be selected for high power density, restricted ventilation or special environmental conditions. | Cooling affects enclosure size, auxiliary power, noise, maintenance and performance at elevated ambient temperature. | Verify heat-loss data, cooling redundancy, filter maintenance, coolant quality and derating above the reference ambient temperature. | High |
| Enclosure and Environment | Typical installations use indoor metal-clad enclosures; the required ingress protection, corrosion resistance and hazardous-area interface depend on the site. | Dust, moisture, salt, vibration and altitude can reduce insulation life and cooling performance. | Specify ambient temperature, humidity, altitude, seismic conditions, pollution level, enclosure rating and installation location. | Critical |
| Safety and Arc-Flash Design | May include medium-voltage isolation, grounding switches, interlocks, segregated compartments, pressure-relief provisions and arc-resistant construction where specified. | Safety design reduces personnel exposure and supports controlled maintenance and operation. | Confirm applicable IEC, IEEE, NEC or local requirements, arc-fault classification, access control and lockout procedures. | Critical |
| Protection Functions | Common functions include overcurrent, overvoltage, undervoltage, overload, ground fault, motor stall, phase loss, thermal monitoring and power-module fault detection. | Protection must coordinate with the motor, transformer, upstream switchgear and process controls. | Review protection settings, selectivity study, event records, fault codes and emergency-stop behavior. | Critical |
| Control and Communications | Typical interfaces include hardwired I/O, serial communication and industrial Ethernet protocols selected for compatibility with the plant control system. | Reliable integration improves monitoring, diagnostics, interlocking and production control. | Confirm protocol support, redundant network options, time synchronization, cybersecurity controls and required signal lists. | High |
| Reliability and Redundancy | Redundancy may be provided through modular power cells, bypass arrangements, duplicated controls or spare-component strategies, depending on the design. | Redundancy can reduce unplanned downtime but may increase capital cost, enclosure size and service complexity. | Compare availability targets, mean time between failures, bypass transfer conditions, spare parts and repair procedures. | Critical |
| Standards and Testing | Evaluation may reference IEC 61800-5-1, IEC 61800-3, IEC 62271 series, IEEE 519 and relevant local electrical codes, depending on scope. | Standards provide a common basis for electrical safety, EMC, performance, switchgear construction and acceptance testing. | Request type-test evidence, routine-test records, factory acceptance test procedures and a clear standards compliance matrix. | Critical |
| Serviceability | Important features include front access, modular replacement, diagnostic software, condition monitoring and safe isolation procedures. | Shorter repair time improves plant availability and reduces the cost of specialist field service. | Assess mean time to repair, technician training, spare-part lead time, remote support and local service capability. | High |
| Total Cost of Ownership | Includes purchase, engineering, transformer or filter equipment, installation, commissioning, energy loss, maintenance, downtime and end-of-life costs. | The lowest initial price does not necessarily provide the lowest lifecycle cost. | Use the same load profile and electricity assumptions to compare lifecycle cost over the planned operating period. | Critical |
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