Description of the Thermal Magnetic Breaker component in Schematic Editor.

The Thermal Magnetic Breaker component models the behavior of a thermal magnetic circuit breaker, such as those commonly found in residential applications.

In Table 1 the schematic symbol and properties window of the Thermal Magnetic Breaker are shown.

Table 1. Thermal Magnetic Breaker in the Residential Energy library
Component Component dialog window Component parameters

thermal magnetic breaker 01

thermal magnetic breaker 02 thermal magnetic breaker 03 thermal magnetic breaker 04

  • Phases

  • Nominal current (A)

  • Instantaneous trip current (A)

  • Manual trip

  • Reset

  • Enable switch feedback

  • Trip temperature (°C)

  • Ambient temperature (°C)

  • Thermal resistance (K/W)

  • Thermal time constant (s)

  • Execution rate (s)

Thermal Magnetic Breaker internal structure

The internal structure of the Thermal Magnetic Breaker is shown in Figure 1.

thermal magnetic breaker 05
Figure 1. Schematic diagram of the Thermal Magnetic Breaker component

Protection Modes

There are three tripping mechanisms within the Thermal Magnetic Breaker component: magnetic trip, thermal trip, and manual trip. Magnetic trips occur anytime instantaneous current reaches or exceeds some threshold value.

\[T_{magnetic} = |i_{inst}| \ge i_{thresh}\]

The threshold current \$i_{thresh}\$ in this equation is set by the Instantaneous trip current property on the component mask.

Thermal trips occur when the temperature of the circuit breaker exceeds some threshold temperature. Heating is modeled using a Thermal Network component to represent a Foster thermal network. The thermal network itself is configured on the Thermal tab of the component mask.

\[T_{thermal} = T_{CB} \ge T_{trip}\]

Manual trips can be caused by writing to the Trip SCADA Input. Manual trips are triggered by rising edge events in the Trip signal.

The circuit breaker can be reset by writing to the Reset SCADA Input. Reset events are triggered by rising edge events in the Reset signal.

Status Indicators

The status of the Thermal Magnetic Breaker component can be assessed using included probes.

Table 2. Status indicators

Signal

Description

(name).SCtrip

Memory status indicating the most recent trip event was a short circuit or magnetic trip.

(name).OLtrip

Memory status indicating the most recent trip event was a overload or thermal trip.

name.CMD

Integer indicating the most recent detected event of the Thermal Magnetic Breaker component.

The value of the (name).CMD is updated every time a trip or close signal is sent to Thermal Magnetic Breaker component. The value is the decimal representation of the binary signals for manual trip, thermal trip, and instantaneous/magnetic trip. The binary representation is encoded as

\[CMD = T_{magnetic}\cdot2^0+T_{thermal}\cdot2^1+T_{manual}\cdot2^2\]