Downsizing of power supply (inverter) for FA equipment is FA understood globally?

Frequent Issues

Is there any product that can safely replace a large film capacitor in a power supply circuit?

The downsizing of electronic equipment is a common issue regardless of the field. FA equipment (industrial equipment) that handles a large output is no exception. The downsizing of control circuits that mainly consist of chip components has rapidly advanced along with the size of chips. On the other hand, the downsizing of power supply circuits that use many large leaded products has not advanced much at all.

Company A, which manufactures industrial motor drive inverters, has been struggling to realize downsizing by replacing large film capacitors used for inverters with another product.

- Example Case: Company A -
Challenge: To use ceramic capacitors while avoiding the risk of short circuit mode failures.

In Company A's inverter design, the screw locking terminals are mounted by soldering after the components are mounted. However, since the snubbing film capacitors mounted near the terminals are too large, it is difficult to perform the soldering without making contact, adversely affecting production efficiency.

In addition, this capacitor has been the bottleneck in terms of downsizing the inverter. Reducing the size of the capacitor would improve design freedom, including the layout of periphery parts, and minimize board size. Replacing the film capacitor with a ceramic capacitor would accomplish downsizing and solve the difficulty in soldering of periphery parts.

Considering the rated voltage and capacitance, a large chip ceramic capacitor could be a candidate. However, since this capacitor is vulnerable to board deflection and often fails by a short circuit mode, it may not be appropriate considering the risk of a power short circuit.

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Since an input fuse is not used in most of Company A's inverters, when the capacitor short circuits, a large current will flow that may cause smoke or ignition. Even if a fuse shuts down the current, the production line of FA equipment would have to be stopped; therefore there is also a possibility of serious damage being generated. For this reason, the important point in selecting a capacitor was to "avoid the risk of a short circuit mode failure (short circuit)."

Company A approached Murata, asking if a large film capacitor used as a snubbing capacitor for removing inverter switching noise could be safely replaced with a ceramic capacitor, and we held discussions to solve the issue. A "lead type multilayer ceramic capacitor" was selected as the method to reduce the risk of a short circuit mode failure, and the downsizing of the inverter was accomplished as planned.

Points of Issue

  • POINT1
    To replace a film capacitor with a ceramic capacitor.
  • POINT2
    To prevent short circuit mode failure of a ceramic capacitor.
The Solution

To examples of replacing a film capacitor with a ceramic capacitor