A SIMPLIFIED METHOD FOR ENERGIZING THE SOLENOID COIL BASED ON ELECTROMAGNETIC RELAYS Munaf Fathi Badr Mechanical Engineering Department, College of Engineering Mustansiriyah University, Baghdad, Iraq E-Mail: munaf@uomustansiriyah.edu.iq ABSTRACT The purpose of this work is to present a simplified, relatively inexpensive and rapid response electrical control system which has been used to energize the The suggested approach involves using electromagnetic relays as main control elements in the control model to meet the requirement of specified proposed control system of the solenoid. The selected solenoid operated in two positions and the control circuit can be easily applied to actuate the solenoid coil in two conduction states either ON or OFF. The laboratory work has been taken place to conduct the theoretical calculations with practical implementation of the solenoid control circuit in conjugated with computer simulations using the required software package such as Matlab were also done to compare the theoretical and practical results. The obtained results showed that the ability of employing the electromagnetic relays in the proposed control circuit of solenoid with fast response and high reliability. Keywords: solenoid coil, electromagnetic relays, electrical control unit, computer simulation. INTRODUCTION In the last decades, the solenoid has been used and employed in wide variety range of several engineering applications especially in mechatronics applications [1]. It was frequently used as a control element that provided the requirements of fast and safe switching tasks involving low control power in addition to compact controller design [2, 3, 4]. Actually solenoid that contained movable iron part behaves as a magnet device that converts the effect of the electrical energy into mechanical motion [5]. It can be considered as an electromechanical actuator device which has been made of a coil consists of long wire winding in a closed loop and producing a magnetic field corresponding to the electrical current flows through a wire [1]. According to the various manufacturing types of the solenoid, it can be mainly divided into two categories that both energized with direct current (DC) or alternating current (AC) and associated with corresponding values of voltage level [6]. In this work, the suggested energizing circuit of the solenoid coil has been taken into account the main electrical and magnetic properties of the solenoid. It contains electromagnetic relays, electrical switches and voltage converter circuit with one or several electrical inputs to provide the required action of the solenoid. The basic role of the implemented relays are to control the operation of the solenoid via provided (ON-OFF) conduction states for the coil and thus control the direction of motion of iron movable part. The suggested approach comprises of the following sections, basic construction of solenoid, and the design of electrical driver circuit followed by the experimental and theoretical work as well as the results and the conclusions. BASIC CONSTRUCTION OF SOLENOID The solenoid coil consists of conductor wire wind with number of turns on suitable size and shape around encapsulated frame. The coil of the solenoid surrounds a movable core which has placed in the center of the solenoid and frequently made of iron metal and named as plunger or armature as shown in Figure-1 [1]. Figure-1. The schematic diagram of solenoid. The solenoid has two subsystems; electric and magnetic subsystem which have made the main construction of it. The operation of the solenoid can be obtained according to the electrical current passing through the coil in the electrical subsystem. As the solenoid is energized with the required level of the electrical energy, then the magnetic field will be set up and the plunger will be moved in a straight line motion inside the existing hollow in the solenoid frame. The motion of plunger is proportional to the producing magnetic force [5, 6]. Practically the coil of the solenoid has a considerable value of electrical resistance, therefore the electrical circuit of the solenoid can be represented as a series combination of passive electrical elements involving inductor and resistor elements as shown in Figure-2[6]. 8750
Figure-2. The electrical circuit of the The calculated value of inductance of the coil preliminary depends on physical dimensions and basic construction of the solenoid. These factors includes the number of turns of the coil, the cross sectional area of the solenoid, the length of the solenoid coil as well as the magnetic permeability of the core material.hence,they can be mathematically formulated as in the following equation:-[5] l 2 L N A Where l = the length of the coil (m); A = the cross sectional area (m 2 ); N = the number of turns (t); And µ = the permeability (Wb/Am). (1) Figure-3. The schematic diagram of the driving circuit of the In this design the control circuit includes switches and relays elements which have been used to control the direction of motion of the plunger inside the solenoid. The DC power source will generate the required electrical energy of the control circuit and the relays are used as a two position controlled switch with two states of conduction states either ON or OFF. The control process of relays depends on the voltages that applied to the coil of the relays as shown in Figure-4. The lost in the electrical energy that caused by the resistance of the coil and dissipated as heat in the solenoid coil can be estimated according to the quality factor formula as shown in the following equation: - [6] 2 I X L X L Q I 2 R R (2) Where Q X L And I 2 X L I 2 R = the quality factor of a coil; = the inductive reactance of the solenoid (Ω); = the stored energy (W); = the dissipated energy (W). DRIVER AND CONTROL CIRCUIT OF SOLENOID A suggestion design of control and driving circuit of the employed DC solenoid coil can be depicted as shown in Figure-3. Figure-4. The operation of electromagnetic relay (a- OFF state, b- ON state). According to the sequence of the control process in the controller unit, the solenoid will be actuated and the plunger of the solenoid will be moved in linear motion with forward or backward direction depending on the control signal that reached to coil of the solenoid as shown in Table-1. 8751
Table-1.State of conduction of relays and solenoid coil (0=OFF, 1=ON). Relay1 Relay1 (contact) Relay2 Relay2 (contact) Solenoid Solenoid (plunger motion) 0 1 0 0 1 0 0 0 1 0 0 1 0 1 1 0 No motion 1 forward 1 backward EXPERIMENTAL WORK AND RESULTS In the experimental work, the control circuit of the solenoid coil has been designed and implemented in laboratory as shown in Figure-5.As mentioned previously the control circuit consists of two relays, electrical switches as well as DC power supply. These electrical apparatus have been wired together via conductor wires to feed the In the laboratory application of the suggested control circuit the voltages supplied from the source can be varied in the range lies between 0V and 24V.The selective level of applied voltage depends on the properties of the Consequently the electrical current of the solenoid can be determined and the value of its electrical resistance coil can be measured. of the solenoid will be moved in forward direction. If the relay (R1) is turned off, then the coil will be de-energized and the relay (R2) will be responsible to return the plunger toward its original position. This process is continually repeated in regular steps and the obtained results can be listed as shown in the Table-2. Table-2.The voltage, current and resistance of Applied voltage Current (A) Resistance (Ω) 0 0 0 4 0.0139 287.769 8 0.0278 287.769 12 0.0417 287.769 16 0.0556 287.769 20 0.0694 288.184 24 0.0833 288.115 Since the solenoid can be represented as an electromechanical subsystem with input energy and corresponding output energy,therefore the energy which has been stored in the coil of the solenoid can be calculated according to the following equation :-[6] While the voltage throughout the hollow of the solenoid will be determined as in the following: I Vgap L t (3) Therefore, with using the appropriate values of the voltage applied to the solenoid, and assuming the switching time is equal to (1µs) for the latching (ON) state in the relay contact, then the theoretical results of the voltage in the gap of solenoid and the energy stored in the coil can be obtained as shown in Table-3. Table-3.The current, energy stored and voltage gap of Figure-5. Laboratory test bench of a solenoid. The sequence of the control process was started as soon as the power supply has been energized. The electrical current is going to pass through the coil of relay (R1) and thus the contacts of relay (R1) will be closed. AS the current reach the coil of the solenoid; the magnetic field will be established in the coil leading to the plunger Applied voltage Current (A) Energy stored (W) V(gap) 0 0 0 0 4 0.0139 0.0001 1.25 8 0.0278 0.0003 2.50 12 0.0417 0.0008 3.75 16 0.0556 0.0014 5.00 20 0.0694 0.0022 6.25 24 0.0833 0.0031 7.50 According to the results in Table-2,it can be noted that current is directly propertional to the volage 8752
across the So, MATLAB script can be used to find the relation between voltage and current in the solenoid coil ant it has been plotted as shown in Figure-6. Whereas the resistance of the selected coil that responsible on the dissipated energy in the coil has been estimated as shown in fighure (7). As mentioned in table(3) the relation between the energy stored in the coil of the solenoid versus current and the relation between voltage across the gap of solenoid against current can be plotted as shown in Figures (8 ) and (9 ) respectively. Figure-8. The energy stored in the Figure-6. The current versus voltage of Figure-9. The voltage of the gap of the solenoid. Figure-7. The level of electrical resistance of the selected CONCLUSIONS In this paper a suggested control system using electromagnetic relays for actuating the solenoid coil was proposed. The laboratory test bench has been set up involving the prototype of manufacturing solenoid maintain the control circuit of the solenoid coil and the demands of control action. Based on the obtained practical and theoretical results, it can be concluded the following remarks: a) The implemented relays have been driving the solenoid coil with fast and very quickly response. b) As the voltage applied to the solenoid coil increased, then the gap voltage in the hollow of the solenoid will be increased. c) As the supplied current increased, the energy stored in the coil of the solenoid will be increased. 8753
d) The obtained results of the simulation were agreed with the experimental results. Therefore, the application of suggested control model in this work was effective. e) However the coils of solenoid and relays elements were successfully implemented in the control circuit, the proposed control circuit of the solenoid can be modified to achieve better performance. ACKNOWLEDGEMENTS The author would like to express his sincere thanks to college of engineering in Mustansiriyah University for providing available support for this research. REFERENCES [1] R. H. Bishop, the Mechatronic Handbook. 2002. The Instrumentation Systems and Automation Society, chapter 20, CRC Press LLC. [2] Munaf F. Badr. 2012. Employing Analogue and Digital Solenoid Hydraulic Valves in Position Control System, Engineering and Development Journal. 3: 269-286. [3] Munaf F. Badr. 2014. Modeling and Simulation of Closed Loop Controlled DC-DC Converter Fed Solenoid Coil, Contemporary Engineering Sciences. 5: 207-217. [4] Munaf F. Badr, Yahya Abdullah and Ahmed Kadhiam Jaliel. 2017. Position Control of the Pneumatic Actuator Employing ON/OFF Solenoids Valve, International Journal of Mechanical & Mechatronics Engineering. 17: 29-37. [5] Boylestad R.L. 2013. Introductory circuit analysis, Pearson New International Edition. [6] Charles K. Alexander and Matthew N. O. Sadiku. 2009. Fundamentals of Electric Circuits, 4th edition, McGraw-Hill. 8754