Introduction
　TTU on the distribution transformer low-voltage side of the three-phase voltage and three-phase current AC sampling (through the transformer), can capture and save a variety of transformer operating data, in accordance with the set parameters to achieve the transformer temperature control, On - load regulation and reactive switching control. TTU products have a communication interface, through the communication network, with the distribution network SCADA system to exchange data, to achieve the main station of the transformer telemetry, remote, remote control function. This paper mainly introduces the application of power module in TTU.

　1、The basic functions of TTU
　TTU is a remote terminal that monitors, measures and controls the various operating parameters of a distribution transformer. It is the distribution network monitoring terminal layer, responsible for the data collection and operation of the implementation of the order; is also the last level of distribution automation monitoring unit, responsible for monitoring the distribution of low voltage measurement voltage, current, frequency, calculate the distribution of active power, no Power, active power, reactive power, power quality analysis, statistical power data.
　TTU generally has three major functions: data acquisition, data control and data communications
　Data acquisition: In the power supply and distribution system, TTU collects and controls the distribution transformer information, real-time monitoring the operation condition of the distribution transformer, and can transmit the collected information to the main station or other intelligent devices, provide the distribution system Operation control and management of the required data.
　Data control: the general requirements TTU real-time monitoring of the line, the column with the distribution or box-type distribution of the operating conditions, the timely detection and handling of accidents and emergencies, and local and remote reactive power compensation and on-load regulation.
　Communication function: According to the requirements of distribution automation system, the distribution transformer terminal TTU should be able to communicate with the distribution station or master station, the real-time information collected by the terminal, and receive the various control Command, the next request can be with the nearby distribution monitoring terminal (TTU) or other intelligent devices to communicate.

　2、The power module in the TTU system applications

　Option One:

　Option two：
　The system power supply instructions are as follows:
　Option 1: integrated charging power, AC / DC power output 27V voltage, all the way to the DC / DC module power supply, the other way to the battery power supply; when the electricity when the battery, the battery to provide backup power. DC / DC power supply provides three separate isolated DC, 5V to the serial communication module power supply; 5V as AD conversion module, microprocessor chip and digital circuit of the total power; 12V as a switch input and output module power supply. To meet the MCU chip 3.3V and 1.8V power requirements, you can also use LD0 to 1.8V and 3.3V power supply for MCU use.
　Option 2: more commonly used, the overall cost is low. AC / DC power supply, three-phase four-wire input, A, B, C, N any one phase of the power supply can work properly. Output for the three-way isolation output voltage, +5.5 V, +13 V, +13 V, and then converted to different voltages required by the system.

　3、The power module in the TTU control system application selection program
　In the above TTU power supply system, the use of switching power supply and battery automatically switch power supply mode. The main power supply is generally used high-power 50W AC / DC charging power. The power supply for the two output, all the way to the post-board power supply, the other way to the battery charge. When the mains power, the charge power inside the need to have the battery management function can automatically switch to the battery power supply to ensure the normal operation of the entire system.
　DC-DC power supply modules that supply power to the switch module, AD conversion module, and microprocessor chip and digital circuit are required to have a wide voltage input regulator output to output a stable voltage when the system supply voltage fluctuates. When the battery power supply, low load power and light load high efficiency DC-DC power supply module, can help the battery to reduce energy consumption, extended working hours. In addition, because the TTU system is generally exposed to the outside, affected by the environmental temperature changes, it requires the power module operating temperature range of at least -40 ℃ ~ +85 ℃.
　In the TTU power supply system, the main control board needs 5VDC power supply to the internal AD conversion module and microprocessor chip and digital circuit power supply. We recommend the power module with 9-36V wide input voltage range, can output 5V stable voltage to the back-end equipment power supply; full load range with high efficiency, standby power consumption as low as 0.12W, can reduce the battery energy loss; also have -40 ~ +85 ℃ industrial grade operating temperature range and output overvoltage, overcurrent, short circuit protection and other multiple protection. It is also recommended that the same series of 6W third-generation DC-DC power supply module URB2412YMD-6WR3 to the switch module power supply.
　TTU in addition to data acquisition and control functions, another important function is the communication function. According to the requirements of the distribution automation system, the distribution transformer terminal TTU should be able to communicate with the distribution station or the master station, report the real-time information collected by the terminal, and receive the various control commands issued by the sub-station / (TTU) or other intelligent devices. Therefore, the distribution of communication functions to monitor the terminal more stringent requirements. Here I recommend the Secretary of the B0505S-1WR2 to 485/232 and CAN communication power supply. B0505S-1WR2 with 1500VDC isolation voltage, small size, efficiency up to 80%, ultra-wide temperature range -40 ~ +105 ℃, TTU to meet the harsh operating environment.
　Program two is more economical program, three-phase four-wire input, A, B, C, N any one phase of the power supply can work properly. The main electromagnetic compatibility index according to the power of four related standards, with good electromagnetic compatibility and anti-jamming capability. More full protection, to ensure the reliability of the customer system.      

　SumUp:
　Taipen Electronics will be based on the TTU system on the demand for power modules, research and development to produce more suitable for the industry application of power modules, power supply TTU industry development.