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Carling Technologies circuit breaker product lines offer a wide range of circuit configurations:
Series Trip
The Series Trip is a basic two terminal device usually used as a combination power switch and overload protector. The contacts and current sensing coil are connected in series with the line and load terminals.
Series Trip with Auxiliary Switch
The Series Trip with Auxiliary Switch is a the same as a Series Trip except with the addition of a single pole double throw (SPDT) snap-action switch which is electrically isolated but mechanically linked to the movement of the main circuit breaker contacts. This switch is commonly used to remotely signal the status of the breaker (ON or OFF/TRIPPED).
Series Mid-Trip with Auxiliary/Alarm Switch
This circuit is similar to the Series Trip with Auxiliary Switch except the single pole double throw (SPDT) auxiliary switch is actuated only upon the electrical trip of the breaker. Upon electrical trip, the normally open (N.O.) contact closes and the normally closed (N.C.) contact opens. This can be used to remotely signal the TRIPPED status of the breaker. Also, upon electrical trip, the handle moves to the "mid" position as opposed to the "full-off" position typical of other breakers. This gives a specific visual panel indication of a TRIPPED breaker as compared to one that is merely turned OFF. Series Mid-Trip is also available without Auxiliary/Alarm Switch.
Series Trip with Remote Shutdown
This configuration is designed for "dump" circuits or "panic" circuit applications. It is the same as a Series Trip but with an additional self-interrupting voltage coil pole, usually of opposite polarity, for remote shutdown. In the example below, a momentary voltage pulse to Pole 2 will shut down both Pole 1 and Pole 2. Because the voltage coil in Pole 2 is self-interrupting, no additional components such as auxiliary switches are required to activate the voltage coil pole. This extra pole configuration is usually required by World Approval Agencies.
Dual Coil with Remote Shutdown
This circuit is similar to the Series Trip with Remote Shutdown except an extra pole is NOT required. A Dual Coil breaker has two coils in the space normally occupied by a single coil. A current coil is used for overload protection and the instant trip voltage coil can be used for remote shutdown. Approximately 30 watts minimum is required to activate this type of voltage coil.
Two Dual Coil options are available. The most common is the Relay Trip Dual Coil, a four terminal device in which the voltage coil circuit is electrically isolated from the current coil circuit. This allows the triggering of the voltage coil from an independent voltage source separate from the line voltage. As such, a DC pulse to the voltage coil can be used to shutdown a primary high energy AC circuit. However, because voltage coils are rated for intermittent duty, provisions must be made to disconnect the power source from the coil after tripping.
The other circuit option is the Shunt Trip Dual Coil, a three terminal device with one side of the voltage coil internally connected to the primary circuit. The other side of the voltage coil is connected to an external third terminal on the bottom of the breaker. This circuit option uses line voltage for dual coil activation, saving wiring costs and resulting is a self-protecting voltage coil.
Care must be taken to avoid mis-wiring of the primary and secondary voltage coil circuits. Mis-wiring could lead to damage to the voltage coil and/or its power source. Contact your local Carling Technologies Sales Representative for all Dual Coil applications.
Relay Trip
The Relay Trip configuration is a four-terminal device, where the contact and coil circuits are electrically isolated but mechanically linked. An overload in the coil circuit will cause the contact circuit to open. These circuits may be of opposite polarity, and are commonly used in "dump" circuit, "panic" circuit, and remote shutdown applications. (Note: World Approval Agencies may require a more electrically isolated voltage coil pole for this function, see "Series Trip with Remote Shutdown" circuit.)
Shunt Trip
A Shunt Trip configuration is a three terminal device similar to the Series Trip but with the addition of a third terminal between the contacts and the coil. This circuit is usually used to control two separate loads (A& B) from the same power source, while sensing overload current in only one load (B). It should be noted that overload protection is not provided in the load (A) circuit, and if needed, must be provided by other means. Also, the sum of the current in circuit A & B must not exceed the contact rating of the device.
Another application possibility occurs when a voltage coil (rated for line voltage) is used. Here the load (B) terminal is connected in series with a normally open (N.O.) pushbutton switch or similar control device. With this, a line voltage pulse through the coil can be used as a means of remotely opening the load (A) circuit. Because the voltage coil is self-interrupting, no additional components such as auxiliary switches are needed in the load (B) circuit.
Switch Only
The Switch Only circuit is the same as a Series Trip, but without a sensing coil. It functions as a low cost, heavy-duty switch when overload protection is not needed. The Switch Only configuration is available with and without an auxiliary switch.
A circuit breaker is an electrical switch that automatically opens a circuit when certain electrical conditions are met. In general, circuit breakers open (trip) when the electrical current through a sensing device exceeds a pre-established current rating. Carling. Technologies' manufactures circuit breakers with a hydraulic/magnetic tripping element. Using the example of the most common circuit configuration, "Series Trip, the following information explains what makes hydraulic/magnetic circuit breakers trip, and how trip time delays are obtained.
What Makes a Magnetic Circuit Breaker Trip?
The hydraulic/magnetic circuit breaker "Series Trip" configuration consists of current sensing coil connected in series with a set of contacts. (Figure 1)
Figure 1
Inside the coil is a non-magnetic delay tube housing a spring-biased, moving magnetic core. An armature links the contacts to the coil mechanism, which functions as an electromagnet. When the contacts are open, there is no current flow through the circuit breaker, and the coil develops no electromagnetic energy. When the contacts are closed, current flow begins. (Figure 2)
Figure 2 - Rated Current or Less
As the normal operating or "rated" current flows through the sensing coil, a magnetic field is created around that coil. When the current flow increases, the strength of the magnetic field increases, drawing the spring-biased, movable magnetic core toward the pole piece. As the core moves inward, the efficiency of the magnetic circuit is increased, creating an even greater electromagnetic force. When the core is fully "in", maximum electromagnetic force is attained. The armature is attracted to the pole piece, unlatching a trip mechanism thereby opening the contacts.(Figure 3)
Figure 3 - Moderate Overload with Induced Delay
Under short circuit conditions, the resultant increase in electromagnetic energy is so rapid, that the armature is attracted without core movement, allowing the breaker to trip without induced delay. This is called "instantaneous trip". It is a safety feature that results in a very fast trip response when needed most. (Figure 4)
Figure 4 - Short Circuit Condition - No Induced Delay
How Various Time Delays are Obtained
The trip time delay is the length of time it takes for the moving metal core inside the current sensing coil to move to the fully "in" position, thereby tripping the circuit breaker. The time delay should be long enough to avoid nuisance tripping caused by harmless transients, yet fast enough to open the circuit when a hazard exists.
If the delay tube is filled with air, the core will move rather quickly, and the breaker will trip quickly. This is characteristic of the Ultrashort trip time delay. Solid state devices, which cannot tolerate even short periods of current overload, should use the Instantaneous trip time delay, which have no intentional time delay.
When the delay tube is filled with a light viscosity, temperature stable fluid, the core's travel to the full "in" position will be intentionally delayed. This results in the slightly longer Medium trip time delays that are used from general purpose applications. (Figure 5).
Figure 5
When a heavy viscosity fluid is used, the result will be a very Long trip time delay. These delays are commonly used in motor applications to minimize the potential for nuisance tripping during lengthy motor start-ups.
By use of magnetic shunt plates within the magnetic circuit, it is possible to divert the magnetic flux, thereby resulting in a higher inrush withstanding capability. These High Inrush trip time delays disregard short duration, high pulse surges (typically 8 ms or less and up to 25x rated current) characteristic of transformers, switching power supplies and capacitive loads.
Hydraulic delay protectors have the added advantage of tripping slightly sooner when operating in higher temperature conditions and slightly longer in lower temperature conditions. This characteristic mirrors the protection needs in most applications. Note that the time delay for tripping changes, but the current required to trip the breaker does not change.
Delay Curves
Each trip time delay type can be graphed to display trip time delay curves. These curves represent the relationship between the percent of rated current and the trip time in seconds.