1 System Description

This TI Design showcases some of the some of the key subsystems that are used in the design of an ac transducer. Some of the key transducer subsystems addressed in this design include a measurement block used for the measurement of ac voltages and currents; a dc analog output block used to communicate the computed voltage, current, frequency, and phase-angle information to a centralized system for analysis; and a digital output block for control and indication, based on the measured parameters during overload or fault conditions. This TI design has the following blocks:

Measurement Block: The measurement block consists of an MCU with a 24-Bit ADC to measure three phase voltages and currents. The voltages are measured using potential dividers, and the currents are measured using current transformers. The MCU computes the voltage and current inputs and computes electrical parameters used for monitoring of the loads.

Data Interface Block: The measured parameters are communicated to remote terminal units or data loggers using different interfaces including RS485, RS232, Wi-Fi, LPRF, or dc analog output. This TI Design showcases interfacing the transducer to remote terminal units using dc analog output. The output can be voltage or current. The output can be programmed for unidirectional output or bidirectional output. The bidirectional output is important to convey the electric parameters with direction. The dc analog output is isolated from the host processing unit for safety. Digital Isolators with low power consumption and enhanced reliability are used against conventional optocouplers.

Digital Output Block: Additional functionalities can be included for protection and monitoring purposes, and one of the functions that can be implemented in a transducer is digital output. The digital output can be used to protect the loads during overloading or used as alarms during the operation of the loads. The above discussed subsystems can be used on the following end equipment:

• AC Transducer: Monitoring of the critical loads is an important factor for increasing power-system efficiency and reducing downtime. One simple way to monitor these loads is by using transducers. Transducers monitor different electrical parameters and report those parameters to a monitoring system digitally using an RS-485 communication interface or by using dc analog outputs, which can be current or voltage. An ac transducer measures a wide range of input currents and voltages and has dc analog outputs, digital outputs, and light-emitting diodes (LEDs) to indicate the status.
• Power Quality Meter (PQM): A PQM is an ideal choice when continuous monitoring of a three-phase system is required. It provides metering for current, voltage, real and reactive power, energy use, cost of power, power factor, and frequency. Programmable set points and assignable output relays allow control functions to be added for specific applications. This includes basic alarm on over- or undercurrent or -voltage, unbalance, demand-based load shedding, and capacitor power-factor-correction control. More complex control is possible using the four switch inputs which also can be used for status such as breaker open or closed, flow information. and so forth.