Shunt Trip Breaker
- Thread starter juanhorta
- Start date
- Status
bdarnell
Senior Member
- Location
- Indianapolis, IN
- Occupation
- Retired Engineer
Re: Shunt Trip Breaker
See here:
http://www.maintenanceresources.com/referencelibrary/ezine/eleccircbreak5.html
See here:
http://www.maintenanceresources.com/referencelibrary/ezine/eleccircbreak5.html
Re: Shunt Trip Breaker
juanhorta,
Since you asked..........
As long as this forum is commonly involved in molded case circuit breakers I'll direct my reply in that regard.
Shunt trips (ST) are basically a simple solinoid that when the coil is energized either it extends a rod of pivots a lever or other action that usually hits the trip bar or other tripping mechanism in the breaker causing it to trip.
It is common for the ST to be activated with an external momentary push button which competes a circuit to energize the ST which trips the breaker. There are other protective device with N/O contacts that are used also such a an external GF of fire protection device.
It must be remembered that the ST coil will fry if left energized for more than a very brief time.
As an integral part of the ST assemble a cut-off switch is provided which is wired in series with the coil. When the breaker is closed this switch is closed. When the external connections of the ST are energized the coil trips the breaker and the moving contacts of the breaker snap up and hit a lever which opens the cut-off switch contact and immediately removes power to the coil.
So, the leads to the coil can continue to be energized after the breaker trips. In my experience the only event that may fry a ST coil is if a voltage is applied to the coil that isn't sufficient enough to trip the breaker but enough to cause the coil to get hot a burn up.
The voltage of ST coils must be specified for you application. Most applications are 120ac but are commonly available in standard voltages down to 12v for many breakers.
Remember that when a ST is installed in a breaker and the breaker is in the open or tripped position the ST cicuit will be open. Should you want to do a continuity check to check the circuits function you should only have continuity when the breaker is closed.
As a side note, large insulated case, air, and power breakers commonly are stored energy devices where you must charge a spring by pumping a lever. The you push a button to close the breaker and another to open it. A solinoid operated spring release mechanisms releases the springs that hold the contacts closed releasing them to the open position. So you may not find the word "shunt trip" used with those but the term "spring release mechanism."
Dave
juanhorta,
Since you asked..........
As long as this forum is commonly involved in molded case circuit breakers I'll direct my reply in that regard.
Shunt trips (ST) are basically a simple solinoid that when the coil is energized either it extends a rod of pivots a lever or other action that usually hits the trip bar or other tripping mechanism in the breaker causing it to trip.
It is common for the ST to be activated with an external momentary push button which competes a circuit to energize the ST which trips the breaker. There are other protective device with N/O contacts that are used also such a an external GF of fire protection device.
It must be remembered that the ST coil will fry if left energized for more than a very brief time.
As an integral part of the ST assemble a cut-off switch is provided which is wired in series with the coil. When the breaker is closed this switch is closed. When the external connections of the ST are energized the coil trips the breaker and the moving contacts of the breaker snap up and hit a lever which opens the cut-off switch contact and immediately removes power to the coil.
So, the leads to the coil can continue to be energized after the breaker trips. In my experience the only event that may fry a ST coil is if a voltage is applied to the coil that isn't sufficient enough to trip the breaker but enough to cause the coil to get hot a burn up.
The voltage of ST coils must be specified for you application. Most applications are 120ac but are commonly available in standard voltages down to 12v for many breakers.
Remember that when a ST is installed in a breaker and the breaker is in the open or tripped position the ST cicuit will be open. Should you want to do a continuity check to check the circuits function you should only have continuity when the breaker is closed.
As a side note, large insulated case, air, and power breakers commonly are stored energy devices where you must charge a spring by pumping a lever. The you push a button to close the breaker and another to open it. A solinoid operated spring release mechanisms releases the springs that hold the contacts closed releasing them to the open position. So you may not find the word "shunt trip" used with those but the term "spring release mechanism."
Dave
- Status