Working Voltage Ratings for Inductors

The first 3 posts we had, we discussed about MEMS, Power Electronic Driver ICs, and Laser Diode Drivers. First, we had MEMS enable medical innovation. These systems make medical equipments more efficient and life-saver. Second, we had power electronic components for materials handling. Power electronics may be small but these components help drive heavy machinery. Variety of drives can be found in lift trucks, and other materials handling equipment. Then we had differential ultra-fast laser diode driver. Technically, it is an ultra high-speed differential laser diode driver designed specifically to drive single junction laser diodes in a differential fashion.

Next up, do you know why voltage rating are not specified on inductor data sheets? Well, voltage ratings of other electronic component are always indicated in the data sheets. It is a requirement. But inductors are different, voltage ratings are not specified on the data sheets. 

Definition of Voltage Rating 

The voltage rating of an inductor is the maximum voltage that can be applied to the terminals without causing arcing or insulation breakdown. Voltage above the maxi- mum rating may cause short circuits between turns, through the insulation, or from the windings to core or frame. 


Calculation 


The large number of construction variables – turn count, wire insulation type and thickness, the layering of the windings, bending or forming crossover leads – makes it difficult, if not impossible, to calculate the theoretical voltage limit of an inductor. 


For example, there are standard test methods for determining the voltage rating of film insulated magnet wire, which generally has a voltage rating in the hundreds, if not thousands, of volts. This rating can easily be compromised by the wire forming process necessary to wind an inductor. Magnet wire can be stressed, crazed or nicked, even in a carefully controlled manufacturing environment. A small scratch in the wire can cause arcing or breakdown at a voltage much lower than the wire "catalog" rating. To calculate a rating that includes these variables is not practical. 

Conclusion (The Good News) 

It might seem that choosing an inductor is nearly impossible. The good news is that all the factors that make it difficult to test or calculate an inductor voltage rating make it unnecessary to test. The vast majority of applications require inductors to be operated at very small working voltages - usually just a few volts. Remember, most inductors work by impeding current flow, not through high voltage induction. Almost all commercial inductors are good for a few volts or even tens of volts with no worries. So for most applications, inductor voltage rating is not a concern. 

For applications that operate from high line voltages or work by induction of high voltage across the winding, it is necessary to consider the possible breakdown of the inductor windings. In these cases it is recommended that the specific application be discussed with the inductor designer/manufacturer and a test plan developed to ensure the suitability of the inductor. 

To learn more about Working Voltage Ratings for Inductors, click on the link below:
http://www.eeweb.com/company-blog/coilcraft/working-voltage-ratings-for-inductors/