An opposed louvre type damper is used to regulate air flow to a furnace in order to control the furnace temperature. The minimum and maximum louvre openings are 10 degrees and 90 degrees respectively. An angular actuator of the electronic type operates the louvres and it is controlled with 0-10V (0 degrees to 90 degrees opening). It gives a feedback of 0-10V relative to the actual position. The PLC analogue input and output cards are 4-20mA loop, but transmitters are used to linearly scale 0-10V to 4-20mA. a) Calculate the mA's that the PLC will read as feedback when the louvres are at 10 degrees. Instead of using louvres to regulate air flow with a fan motor running at constant speed, we can use a VSD (Variable speed drive) to regulate the air-flow by varying the motor speed thereby conserving energy. b) If the VSD is controlled by a 4-20mA loop regulating the speed of the motor, calculate the mA required to set the motor to run at 50% speed?
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An opposed louvre type damper is used to regulate air flow to a furnace in order to control the furnace temperature. The minimum and maximum louvre openings are 10 degrees and 90 degrees respectively. An angular actuator of the electronic type operates the louvres and it is controlled with 0-10V (0 degrees to 90 degrees opening). It gives a feedback of 0-10V relative to the actual position. The PLC analogue input and output cards are 4-20mA loop, but transmitters are used to linearly scale 0-10V to 4-20mA.
a) Calculate the mA's that the PLC will read as feedback when the louvres are at 10 degrees. Instead of using louvres to regulate air flow with a fan motor running at constant speed, we can use a VSD (Variable speed drive) to regulate the air-flow by varying the motor speed thereby conserving energy. |
b) If the VSD is controlled by a 4-20mA loop regulating the speed of the motor, calculate the mA required to set the motor to run at 50% speed?
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