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Showing results for tags 'DELTA'.
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Motor Star Delta Starter for PLC Program
leizuofa posted A plc and hmi english article in PLC programming learning
When electric motor is started, it draws a high current typical 5-6 times greater than normal current. In DC motors there is no back emf at starting therefore initial current is very high as compared to the normal current. To protect the motor from these high starting currents we use a star and delta starter. Simply in Star connection, supply voltage to motor will be less. so we use star connection during starting of the motor, after motor running we will change the connection form star to delta to gain full speed of the motor. Star Delta Motor Starter The following figure shows the winding connections in star and delta configuration one by one. It can be seen that in star connection, one end of all three windings are shorted to make star point while other end of each winding is connected to power supply. In delta configuration, the windings are connected such that to make a close loop. The connection of each winding is shown in above figure. In actual motor the three phase connections are provided in the following order as shown So in order to make winding connection in star and delta style in practical motor, the connection is shown above. Main contractor is used to supply power to the windings. It must be turned on all the time. Initially the star contactor is closed while delta contactor is open It makes the motor windings in star configuration. When the motor gains speed, the star contactor is opened while delta contactor is closed turning the motor windings into delta configuration. The contactors are controlled by using PLC. The following section of PLC tutorial will explain the ladder programming for star delta motor starter. PLC program for star delta motor starter : PLC Ladder Logic Rung 1 Main contactor : The main contactor depends upon the normally open input start push button (I1), normally closed stop button (I2) and normally closed overload relay. It means that Main contactor will only be energized if start button is pressed, while stop is not pressed and overload relay is not activated. A normally open input named (Q1) is added in parallel to the start button I1. By doing so, a push button is created which means that once motor is started, it will be kept started even if start button is released Rung 2 Star contactor: Star contactor depends upon main contactor, normally close contacts of timer (T1), and normally close contacts of output delta contactor (Q3). So star contactor will only be energized if main contactor is ON, time output is not activated and delta contactor is not energized. Timer T1: Timer T1 measures the time after which the winding connection of star delta starter is to be changed. It will start counting time after main contactor is energized. Rung 3 Delta contactor: Delta contactor will be energized when main contactor (Q1) is energized, timer T1 is activated and star contactor (Q3) is de-energized. Also see Programing of push button and other requirements for simple motor starter is explained in PLC Tutorial: Motor starter Note : This post for educational or reference purpose only. For a live circuit, there will be some additions to the above circuit like safety related, as per application, some interlocks etc. -
Modbus Communication between Delta PLC with VFD
leikang posted A plc and hmi english article in PLC programming learning
Modbus communication of delta PLC (DVP 14SS2) with delta VFD (VFD-L series). The motor is to be run directly from HMI (DOP-107CV) using Modbus communication. Delta PLC and VFD Modbus Communication The induction motor is to be run directly from HMI along with its speed control. Speed control is such that there should be two buttons in HMI that increase and decreases the speed of the motor by steps of one hertz (assume). There is a VFD-L series delta AC drive which will run the motor based on the commands received from PLC. Firstly, communication and other parameters need to be set in the drive matching all its configurations with the PLC such as baud rate, parity, communication mode, etc; except the slave ID (station address) which must be different from the PLC station address. By default, the PLC station address is equal to one (1). This means the station address of the drive must be anything in its defined range other than one (1). The detailed parameters to be set for the communication mode are as follows: 2-00 = 4 2-01 = 4 Communication Parameters We have to set the communication parameters as per the above table. (taken from manual). 9-00 = 2 (can be set to anything except 1) 9-01 = 1 9-04 = 7 (RTU mode, stop bits equal to 1 & parity to even) DVP 14SS2 has two communication ports namely RS232 and RS485 separately. Now, the communication port 2 settings need to be done according to the set parameters of VFD which are as follows. Open the WPL soft. (Delta PLC Software) Click on the Communication Program icon on the programming page. Select COM2 and press next. Set the parameters according to the VFD drive communication parameters and click Next. Here, they are fed according to the parameters set in the VFD-L dive. The station address of PLC is 1 (see left bottom corner) Check the highlighted and press next. One can check the boxes below and write the conditions. Here, we are skipping this window, and instead, we will write the logic directly on ladder diagram mode. Click Finish. Now, the following ladder logic is generated as a result of the above set conditions. The ladder in rung 2 executes each time a sent request is received. The ladder in rung 3 executes each time after any data is read from or written to the drive. Now, before moving further, the logic for starting and stopping the motor and its speed control is written, we need to find out the Modbus addresses of the drive through which the said will be executed. For the VFD-L series, 2000H is the Modbus address for starting & stopping the drive and 2001H is for the frequency change. Here, H denotes hexadecimal. In this topic, we are here to use the decimal format for the particular address. So hexadecimal must be changed to decimal format. Through the 8421 code, we would convert as follows: 2000 (Hex) = 8192 (Dec) 2001(Hex) = 8193 (Dec) So, instead of 200H & 2001H, 8192K & 8193K will be used. Make sure that 8192 & 8193 are only the Modbus addresses. If 8192K has a value equal to 10 then the motor will start. If 8192K has a value equal to 1 then the motor will stop. If 8193K has a value equal to 5000 then the motor will run on 50 Hz, which means if the speed of the motor needs to be increased by 1 Hz, 100 must be added to the existing value and vice versa. PLC Program Explanation Now, going to the details of the PLC program. Sending request bit M1122 is set each time any command is given to VFD in rung 5. MODRW K2 K6 K8192 D70 K1 MODRW represents Mod read write K2 represents the station address of the VFD. K6/K3 represents the function code whether to write or read. Here k6 represents write. K8192 represents the Modbus address to which data is written Data in D70 is written to k8192 K1 is the data length 10 (dec) and 1 (dec) are moved to D70 when start and stop commands are given in rungs 6 and 7. At the same time, the transmission of data takes place i.e data in D70 is written to the 8192k address of VFD in rung 8 to start and stop the motor. 100 (dec) is added to D100’s value in rung 10 to increase the speed by 1 Hz when the speed increase pulse (M4) is received. 100 (dec) is subtracted from D100’s value in rung 9 to decrease the speed by 1 Hz when the speed decrease pulse (M5) is received. At the same time, the transmission of data takes place i.e data in D100 is written to the 8193k address of VFD in rung 11 to start and stop the motor. HMI Now, coming to the HMI configuration. After selecting the HMI model, set the below configuration as here, PLC to HMI configuration is on RS232. (You have to configure it as per the HMI model) Take four momentary buttons, assign the addresses, and design the HMI screen as follows: Start = M0 Stop = M1 Increase speed = M4 Decrease speed = M5 Test the process The HMI design is not covered in this article.
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