A system of controlling a wood drying room is supposed to maintain certain humidity and temperature parameters set by a user for the process of wood drying, what optymalized the process of drying. For his purpose a controller cooperates with the throttling valve servos of hot air inlet and the chimneys outlet.
Basic system works based on a controller LB-474. It is a device, which works autonomously, but it has a possibility of communicating with a computer. The cooperation with the computer allows on remote change of the control parameter settings, as well as it allows on parameter registry in a serviced room. The controller has two inputs of a resistance thermometer Pt1000 (a psychrometer with a dry-bulb and wet-bulb thermometer LB-754P) and four control transmitter outputs. The controller has a built-in internal acoustic alarm with a possibility of controlling an outside signaler.
Picture no. 1 The devices cooperating with a regulator LB-474A - the throttling valves of the “chimneys” and hot air inlet, B - wet-bulb and dry-bulb thermometers in a psychrometer LB-754, B - the executive devices (especially ventilators or ventilator sections), S - controller - regulator LB-474.
The executive devices cooperating with the regulator LB-474 are connected through a block of transmitters LB-475 and the devices of big capacity or/ and three-phase require additionally the contactors. Except for the mentioned above devices, the controller can cooperate with other executive devices (i.e. humidifiers, coolers, heaters or ventilators) controlled in a way on/off or three-joint.
The controller switches on the servos closing an inlet of hot air stream and the outlet stream chimneys. The control is performed depending on the set values of temperature and humidity (a psychrometric temperature difference).
The controller LB-474 in a basic version is used for controlling two parameters (temperature and humidity). For regulation a PID algorithm is used, with a possibility of choosing the dynamic parameters of regulation. The way of controlling the servos using a three-joint method with an internal regenerative coupling. The dynamic regulation parameter settings and three-joint signal parameters can be performed from the device’s keyboard. Except for an additional transparent casing, an external keyboard was introduced allowing on a set valve’s change of humidity and temperature. In a basic work mode on the displays the measured values of humidity and temperature displayed. A transition to a parameter change mode after pressing any key button. In a change mode on the displays a parameter number and its values are shown. Return to a work mode is done also after the key buttons are not active for approximately 1 minute.
|MEASUREMENT / CONTROL||SCOPE OF MEASUREMENT
||Chosen scope- possible scope exceeds scope of
||Measurement uncertainty +/- 1,0% + last digit
in the scope 50,1...99,9%
|The servos and other executive devices
||Through selected for a device transmitters and contractors.|
|Period and time of processing
||Regulated 0....100 min
|POWER SUPPLY, CONTROL
|Network power supply||230V 50 Hz|
|Load capacity of a control output (with a transmitter)
||230V / 50Hz / 1A|
|Type of load capacity
For cooperation with a regulator LAB-EL, it is possible to apply the inverters (frequency converters – changing one-phase voltage 230 V / 50 Hz to a three-phase voltage 3 x 230 V / 0...60 Hz) that have a control signal input on/off or allow on controlling through a device switch on. The number of turns has to be set manually or come from a different source. Type of the inverter should be chosen depending on capacity of an engine one has. It is recommended to agree the type of inverter with its producer (distributor, importer) adequately to a ventilator’s engine size (power) owned.
A successful drying room’s work is influenced without a doubt by a user’s recognition of all the details concerning the work devices’ work principle and the methods of choosing the correct regulator settings. The LAB-EL company organizes for the users, distributors and installers the training courses in the scope of the offered devices.