Consult Came to choose the most appropriate IVIC for your project.
The IVIC (Impulse Voltage Insulation Class) defines the ability of an electric motor winding to withstand the electrical impulse stresses generated by inverters or electronic control systems of the PWM type (pulse width modulation). The applicable standard is IEC EN 60034-18-41, which defines the qualification tests and PD tests to assess whether the winding complies with the standard (insulation system free of partial discharges).
No application specifications
If the motor application has not yet been defined (e.g. during the preliminary design or development of a multi-purpose motor platform), the choice of IVIC takes on a preventive role in the case of a motor powered by an inverter.
Under these conditions, IEC EN 60034-18-41 recommends adopting Class C as the minimum level of robustness. This choice ensures an adequate safety margin against the impulse voltages typical of inverters to reduce the risk of dielectric degradation and premature winding failures.
Function of the PD test
The Partial Discharge Test verifies the ability of a winding to withstand impulse voltages (spikes) caused by power electronics. Inadequate insulation can, over time, suffer dielectric degradation, which leads to insulation perforations and short circuits in the winding.
IVIC and selection criteria
The IVIC distinguishes between four severity levels
- Class A – benign;
- Class B – moderate;
- Class C – severe (recommended when there are no application specifications);
- Class D – extreme (used only in rare cases with extremely high voltage spikes).
The choice of class depends on the power supply type, impulse voltage profile, switching frequency of the inverter, and whether there is a connection cable between the motor and inverter, which can amplify the noise generated by the electronics.
Economic aspects and consultancy
- Class A involves lower construction costs; as a rule, it is used with inverters mounted directly on the motor, with modest impulse voltages;
- Classes B and C, instead, require more expensive insulating materials and processes, and stricter testing procedures;
- Finally, class D requires dedicated insulation systems with extremely expensive materials and processes; it is only recommended in extreme cases.
Characterising the winding involves a dedicated study to assess the insulation system adopted.
Came offers a technical consultancy service and laboratory testing to determine the IVIC of the product, and advise the customer on the optimal choice for the required application and reliability level.
Fabrizio Bardelli
Came Research and Development Expert
consulting@came-italy.com
+39 0444 488282
