DISCLAIMER: This topic is for discussing these types of breakers. The 10A "Instant trip" example pictured above might not be right for your application. Choosing the right Amperage rating and Time delay should be based on several factors and less than or equal to the nominal output rating of the transformer to which they are connected. If think you may want to use a breaker of this style and you are unsure of the correct model, please ask for help here in the Electrical Forum in choosing the right one for your application.
Airpax Snapac Hydraulic-Magnetic Circuit Breaker Internal Mechanisms - Updated 5/12/2021
After recently being introduced to these products here on OGR, I'm in the process of learning more about them. This series of hydraulic-magnetic breakers is called AirPax Snapac and is made by Sensata/Airpax. They are sold at OnlineComponents.com
Their data sheet is attached.
There is more information on the web about their larger cousins (for example https://www.youtube.com/watch?v=sJU2pTdUyY0 ) used for higher voltage and amperage circuits, how they work and cut-away animations, but I was unable to find details on the inner workings of these smaller Airpax Snapac hydraulic-magnetic versions.
So, I decided to go ahead and cut one of the Airpax Snapac 10A “Instant” trip breakers open. They are very similar, in that they have an Arc Chute (for dissipating the arc created by the opening contacts when it trips). They also have what appears to be a gas filled piston inside a coil, but there is one subtle difference in the way it activates the trip linkage. As the current in its stationary coil rises towards a set value, the resulting increase in the magnetic field overcomes the spring tension on the disconnect mechanism and pulls on a lever and disengages the contacts.
Airpax Snapac hydraulic-magnetic breakers are available with different time delays before tripping at the rated current (Amps). They come in Instant (0.1 second delay), Fast (which is actually slower than the Instant and the time varies by how much above the rated current the actual current flow through them is for a variable period of time), and Slow (which has delay characteristics similar to a Slow Blow fuse).
Choosing the right type of breaker is dependent upon many factors and choosing correctly can mean the difference between experiencing nuisance tripping before the the optimal current flow is reached in the protected circuits, to just right protection, to being either to slow or overrated and not providing adequate protection to prevent damage to the transformer and what's connected to it.
Here are links to the Airpax Snapac "Instant" trip Series Breakers
5 Amp PP11-0-5.00A-OB-V https://www.onlinecomponents.c...00aobv-10090638.html
7.5 Amp PP11-0-7.50A-OC-V https://www.onlinecomponents.c...50aocv-10090644.html
10 Amp PP11-0-10.0A-OB-V https://www.onlinecomponents.c...00aobv-10090622.html#
12.5 Amp (no button markings) PR11-0-12.5A-XX https://www.onlinecomponents.c...125axx-43802931.html
Links to the Fast and Slow varieties are not included here, but can be found on the same website. Their part numbers differ by having a PP11 -1 - xxxx(Current rating) for Fast, and PP11 -2 - xxxxx(Current rating) for Slow.
Here is some basic information on choosing the correct Amperage rating for a breaker:
There are a few electrical fundamentals in addition to the trip delay time one should understand when choosing a breaker. The transformer Output ratings are a good place to start. Here's what they mean:
Volts - (electrical energy potential) in Conventional operation this sets the train speed.
Amps (current flow) - More Locos, cars and such (and shorts) pull more current through the circuit from the transformer. The transformer only delivers as much current as required by the load, up to a point. This point is it's Output rating.
AC Transformer Output ratings are usually given in either Watts or VoltAmps, both of which have essentially the same meaning when choosing breaker size.
Watts = Volts x Amps = VA
Watts/Volts = Amps
I hope this helps.