Advanced Conversion’s Power Ring capacitors have a high performance design that reduces losses and inductance, while increasing the ripple current rating compared to traditional film capacitor technology. The ring shape construction enables extremely low internal losses (ESR) and minimises the inductive properties (ESL). For example, a 1000 µF – 600 V DC link exhibits ESR values as low as 0.15 mΩ. This performance makes the Power Ring capacitors one of the best DC link capacitors on the market.

 

How good is the thermal performance of a Power Ring?

The graph of temperature versus ripple current below illustrates the huge improvement in thermal performance delivered by the Power Ring design versus a conventional array of film capacitors. This performance improvement translates to a more efficient use of microfarads where high ripple current is an issue. Rather than adding capacitance until the capacitor bank can handle current to achieve the required life (which would result in increased cost and size), the design can be optimised for current handling instead.

Advanced Conversion can provide solutions using PEN HV film, which allows for higher operating temperatures up to 125 ⁰C.

The DC link capacitors are also designed with solid insulation, solving creepage and clearance issues typically found in high altitude and high voltage applications.

Using the Power Ring for a snubberless circuit design

A Power Ring DC link capacitor with integrated bus bar offers a loop inductance that can allow for a snubberless circuit design in some applications. Snubber capacitors get very hot since they are connected to the IGBT pins (often the hottest point other than under the die itself) and are almost never directly cooled due to the difficulty of connecting cooling plates. Their small size and poor cooling mean snubber capacitors are usually the weak link in the reliability chain for an inverter.

As usable operating voltage increases there can be a tendency to add a snubber to get every bit of safe operating voltage out of a system. The integrated Power Ring capacitor is a more effective method of reducing overshoot, and therefore increasing safe operating voltage, without compromising reliability or system lifetime.

Integrating DC link capacitor designs

Advanced Conversion integrated capacitor and busbar assemblies can be fully customised to match customer voltage, ripple current and mechanical requirements. The design capability is very broad with our project team working closely with customers to make sure the optimum solution is delivered.

In short…

A cooler DC link capacitor means a longer lifetime. A lower ESL means reduced overshoot and undershoot, which reduces stress. Removing the requirement for a snubber capacitor means lower costs, a smaller design and a longer lifetime.

Useful links

Power Ring capacitors
Capacitors from PPM Power
Technical Papers