switching losses

What context?

Switching losses in any sense denotes only the transient stage when a switch changes it's state.

In the context in which I am most familiar, it refers to the contact resistance within the switch or switches. Contact resistance is a field of study that few people appreciate. If you go shopping for certain kinds of relays, you will find that the contacts come in a variety of metals and methods, depending on the application.

Down time usually refers to the time in which a machine or process is unavailable.

I have never heard the term "switching loses" applied to actual mechanical switches, they typically don't switch often enough to account for much in losses.

Where I see the term used is in solid state devices such as thyristors or transistors. For example, a transistor used in a PWM firing application such as a VFD, SMPS or UPS system. It will be firing at let's say 15kHz. That means 15,000 times per second, that little switch is turning on and off. In that transition, a very tiny amount of energy is absorbed by the device itself, because energy never stops immediately and nothing is a perfect insulator nor a perfect conductor. No matter how tiny the amount is however, it is cumulative so eventually it is radiated as heat, a form of waste energy. This is what is called the "switching losses" in an electronic system. It is what ends up being the restriction in component design and sizing, because if the switching losses can be kept to a minimum, the devices and all associated devices can be smaller. That is why Cell Phones used to be the size of bricks, but now can be built in to a wristwatch. Improvements in materials have reduced switching losses to such a great degree that the heat given off by components can be easily dealt with.

Do you mean loss of switches due to theft, with down time loss due to switch replacement or recovery?

Can you provide more information on your question and application.

actually i was talking related to power systems.power supply companies,hvac etc.switches include all CBs .now i think you understand the point.

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