article · Machines
Fast-switching pulse-width modulation inverters can cause reflected-wave effects in motor feeder cables, leading to excessive overvoltages. These overvoltages place stress on motor winding insulation, accelerating degradation and elevating the risk of partial discharge. Additionally, common-mode voltages travel across parasitic paths inside the motor, generating shaft voltages that trigger electrical discharge machining currents and premature bearing breakdown. To understand these effects, an experimental evaluation examined the influence of cable length, using one metre, three metres, and 16 metres, and cable type, comparing shielded and unshielded options, on an 11 kW permanent magnet synchronous motor drive system under identical operating conditions. Measurements of line-to-line voltage, line-to-ground voltage, shaft voltage, bearing current, and discharge currents were collected and statistically analysed. The investigation also assessed how motor grounding configurations affect common-mode and bearing currents, providing guidance for selecting appropriate cables in wide-bandgap inverter-fed motor drives.
Modern electric motor drives often suffer from unseen electrical stresses that degrade insulation and destroy bearings ahead of schedule. By identifying how physical cabling and grounding setups alter these damaging voltages and currents, system operators and design engineers can make informed installation decisions to extend equipment lifespan and avoid unexpected drive system breakdowns.
This applied experimental research provides empirical evidence to inform cable selection and grounding practices for wide-bandgap inverter-fed electric drives. It is relevant to drive system integrators, electrical engineers, and industrial motor operators aiming to reduce bearing wear and insulation breakdown. The work represents applied, laboratory-tested research that can directly guide technical standards, system design specifications, and procurement choices in industrial power electronics.
AI-generated from the published abstract. Always read the original work before citing.
Fast-switching transients and high dv/dt associated with PWM inverters exacerbate the reflected-wave effects in the motor feeder cable. This leads to higher motor-side overvoltages, which increase the stress on the motor winding insulation, potentially accelerating insulation degradation and increasing the risk of partial discharge within the motor windings. Moreover, the common-mode voltages at the motor terminals propagate through parasitic capacitive paths within the motor, inducing shaft voltages that lead to electric discharge machining (EDM) currents and premature bearing failure. This paper experimentally investigates the influence of motor feeder cable length and type (shielded and unshielded) on motor terminal overvoltage, shaft voltage, and bearing current behavior in an inverter-fed 11 kW permanent magnet synchronous motor drive system. Three cable lengths (1 m, 3 m, and 16 m) with shielded and unshielded configurations are evaluated under identical operating conditions. Measurements of line-to-line voltage, line-to-ground voltage, shaft voltage, bearing current, and EDM discharge currents are recorded and statistically analyzed to assess the influence of cable configuration. The study also examines the influence of the motor grounding configuration on common-mode current and bearing current behavior. Overall, the findings provide comprehensive insights into the influence of motor feeder cable on overvoltage, shaft voltage, and bearing discharge behavior, supporting informed cable selection for WBG inverter-fed electric drives.
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DOI: 10.3390/machines14090970
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