[VsdBy21] Variable speed control bypass
Program block, name / node subtype: [VsdBy21] Variable speed control bypass
Library hierarchy: Universal equipment
Family: VsdBy
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Configurator
Program blocks are stored in the library without I/Os. Use the auto-create and auto-connect functions to create I/Os and/or to connect them to the interface blocks, e.g., R_A, CMD_B. Alternatively, take the I/Os from the folder containing the predefined I/Os in the library and/or from the plant and connect them to the interface blocks.
Controls a bypass function for variable speed drive (VSD).
If the VSD has a fault, it is automatically bypassed and the motor runs with constant speed, depending on the frequency of the electrical supply, e.g., 50 Hz.
A configuration value object enables the automatic switching to VSD bypass in case of fault (default: True).
The option "Bypass switch" switches on the VSD bypass manually.
The following description focuses on using VsdBy21 in a fan.
If VsdBy21 is used in a fan, it is very likely that this fan is part of an air handling unit.
A parameter in the program defines the behavior of the air handling unit in case of a fault of the VSD of one of the fans:
0 = The air handling unit does not stop and continues running.
The VSD switches off and the VSD bypass switches on after a short adjustable delay, e.g., 10 seconds. After resetting the fault of the VSD, the VSD bypass switches off and after the same short delay, the VSD switches on. This delay depends on the installed equipment.
1 = The air handling unit stops.
The VSD switches off and the air handling unit switches off and remains off for an adjustable period of time, e.g., 1 minute (most likely longer than 1 minute). Then the air handling unit starts again and the fan with the faulty VSD runs on VSD bypass. After resetting the fault of the VSD, the air handling unit switches off and remains off for the same adjustable time. Then the air handling unit starts again and the VSD of the fan switches on. The time for keeping the air handling unit off depends on the installed equipment and settings in the function block CMDSEQ_B.
In either case, the behavior of the other fan in the air handling unit (continuing with the VSD or switching to VSD bypass too) depends on the existence of the option "Follow VSD bypass state from partner aggregate" with the "State" of this fan connected to its interface.
This program block has the following optional functions:
Option: Bypass switch (1xBI)
Switches on the VSD bypass manually if the configuration value object for automatic switching in case of fault is set to "True" (default setting).
Option: Follow VSD bypass state from partner aggregate
Defines the behavior of the VSD bypass of this fan unit (continuing with the VSD or switching to VSD bypass too) in case the VSD of the other fan has a problem and switches to VSD bypass.
Option: Thermoelectrical overload (1xBI)
Reads the thermoelectrical overload signal from the motor and generates an alarm.
Option: Feedback (1xBI)
Reads the feedback signal, e.g., from a fan control unit, and generates an alarm if feedback is missing when the fan must run.
Name | Description | Type | Alarm / Notification class | Trend / Type | |
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Cmd | Command | BO: Binary output | No | Yes, 4 | |
RlsBy | Release bypass | BCnfVal: Binary configuration value | No | No | |
Sta | State | BCalcVal: Binary calculated value | No | No | |
Name | Description | Type | Alarm / Notification class | Trend / Type | |
|---|---|---|---|---|---|
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BySwi | Bypass switch | BI: Binary input | No | Yes, 4 | |
ThOvrld | Thermoelectrical overload | BI: Binary input | Yes, 5 | No | |
Fb | Feedback | BI: Binary input | Yes, 4 | No | |