I. overview:
With the progress of science and technology, the use of electrical equipment in power plants in China is increasing gradually, which makes the normal operation of the motor become the precondition for other equipment to operate normally. Therefore, it is the performance of being responsible for the normal industrial production to select and use the motor controller reasonably. Only on the basis of the normal function of the motor, can we Enough to ensure that the whole industry's workflow will not be disturbed and can operate normally. In thermal power plants, the control principle and application of low-voltage motors have always been a technical problem [1,2].
In the protection design of power plant motor equipment, the application and protection configuration of low-voltage motor can be designed by various schemes. In the past, thermal relay and circuit breaker (or fuse) were used as motor overload protection, phase failure protection, short-circuit protection and control elements. Due to the constraints of the communication function is not flexible enough and other conditions, they have been unable to meet the growing development The new intelligent motor controller can realize heavy load starting and temperature protection of the motor. It also provides a variety of measurement and control functions and a variety of motor control modes, which can meet the protection and control requirements of the motor and effectively guarantee the safe operation of the motor. This paper introduces the practical application of ARD3 intelligent motor controller in power plant.
II. Functional requirements for motor controller in power plant
In the mechanical and electrical industry of our country, the motor is the most widely used. The electricity consumed in the motor accounts for a large part of the total power generation, and all kinds of fans, pumps, air compressors account for more than half of the electricity consumed by the motor. The working environment of the motor in the power plant is very bad, and it is often prone to locked rotor, short circuit, open phase or long-term overload operation [3]. Therefore, the controller should be able to protect and control the motor working in the harsh environment in real time, so as to ensure the normal operation of the motor in the power plant.
According to technical code for design of auxiliary power in thermal power plant (DL / T 5153-2002), LV auxiliary motor shall be equipped with phase to phase short circuit protection, single-phase to ground protection (or single-phase to ground short circuit protection), overload protection, low voltage protection and open phase protection [4]. Therefore, the power plant project needs to measure the voltage and current parameters with communication function, and the controller needs to have self diagnosis output, power-off output, fault record and other functions, which are summarized as follows:
1. Realize perfect motor protection function
The controller collects three-phase AC current, three-phase AC voltage, residual current, PTC thermal resistance value, electric energy and other electrical parameters of the motor, as well as various motion states and other signals during the operation of the motor, through the internal processing and operation of the controller, so as to realize the starting timeout, overload, blocking, under load, phase failure, three-phase current imbalance, residual current (grounding/ Leakage), temperature, external fault, phase sequence, over-voltage, under voltage, under power, over power, te time and other comprehensive protection, so as to ensure the safe and continuous operation of power plant production [4].
2. Realize multiple motor control modes
The intelligent motor controller realizes a variety of different motor starting control through program control. The operation control authority realized by the controller includes: 1) remote control through RS-485 communication interface; 2) operation control through keys on the display module; 3) remote automatic control through Di terminal controlled by DCS system; 4) field local control of Di terminal.
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