- Annunciation System Definition: An annunciation system is a setup that uses devices to announce faults or unusual activities in an electrical or electronic process.
- Alarm Annunciator: An alarm annunciator is an audio-visual system that alerts operators to faults or potential issues, enhancing safety.
- Annunciator Relay: The annunciator relay changes over to activate alarms when faults are detected, ensuring timely warnings.
- Monitoring Faults: Connecting monitoring devices like overvoltage relays or PTC thermistor relays to an annunciator system helps detect and signal faults efficiently.
- Modern Annunciator Components: Modern annunciators use power supply units, programming units, and LED display units for efficient, low-power fault monitoring and indication.
In electrical and electronic systems, an Annunciator is a device that announces faults or unusual activities in the system or process.
What is Alarm Annunciator?
An alarm annunciator is an audio-visual warning system that highlights faults or potential mishaps. It is crucial for safety as it can warn operators before accidents occur. Let’s explore how a typical alarm annunciator operates.
Operation of Alarm Annunciator
Alarm Annunciation System
To understand how an alarm annunciator works, let’s start with a basic process monitoring concept. Suppose an electromagnetic coil is energized by a power supply. If the coil burns due to overvoltage, the process is disrupted. Checking each part to find the fault is time-consuming, especially if you have to monitor 50 such coils.
By connecting a bulb in series with each coil’s power supply, the bulb will glow only if the coil is energized and healthy. This way, you can monitor 50 coils using 50 bulbs, each indicating the status of an individual coil. This is a simple process monitoring model.
An alarm annunciator centralizes fault monitoring by providing audio-visual signals. Modern annunciators use microprocessor or microcontroller circuits for maximum reliability and enhanced features.
Connection of Alarm Annunciator
There are two types of connections for each annunciation system; they are input fault contacts and output relay changeover contacts. Input fault contacts are simple connection normally open (or NC Selectable) with respect to a common C contact. Usually these input fault contacts are potential free contacts. The logic is, if any fault contacts and the common contact C becomes short circuited by any means, the respective fascia or fault window will start blinking, and the output relay contact will changeover instantly.
Suppose, you are using 8 windows annunciation system, which means you are monitoring 8 operations at a time, by the annunciation system. Let us think your fault 1 (F1) is assigned as over voltage alarm of motor 1 and your fault 2 (F2) is assigned as overheating of a motor 2 armature. You will connect an over voltage relay with motor 1 and a PTC thermistor relay with Motor 2, and the respective outputs (Normally open output, changes to close when faulty) of those relays will be connected across F1 (fault input) and C (common), and F2 (fault input) and C (common) of the annunciator system. Therefore, if the voltage of motor 1, is increased beyond the predefined safe level, the over voltage relay will operate and will make a closed loop between F1 and Common. So, the F1 window will start blinking which indicates the motor 1 is getting over voltage. At the same time, the annunciator relay will changeover, and if you connect a hooter previously with its output contacts, then the hooter will start alarming.
Similarly, if the armature temperature of motor 2 is increased beyond the predefined safe level, then the PTC thermistor relay will changeover and will make a loop path between F2 and Common C of annunciation system. So, the F2 window will start blinking which indicates the motor 2 is getting over heated. At the same time, the annunciator relay will changeover, and the hooter connected with its contacts, it will start alarming. Basically, the annunciator output relay changeover is common, irrespective of any faults. A single hooter is used for all fault windows. An auxiliary AC/DC supply is necessary to operate the annunciator and in modern annunciators, there is also a window and connection provided for monitoring its own auxiliary supply.
Modern Alarm Annunciators consist of a power supply unit SMPS, a programming unit CPU and other connections including fault contacts and facial display units. The blinking windows are generally acrylics, which are enlightened by LED with very low power consumption. Typically, annunciation effectively starts from 4 faults that is 4 windows, if the number of faults to be monitored is more than 64, it is preferable to install the programming unit CPU, power supply unit PSU and the display facial unit individually, which ensures the maximum accuracy and effectiveness.
