Zamil MAC-240, Installation, Operation & Maintenance Manual

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4.3 SUPPLY FAN SPEED CONTROL
4.3.1 General description
The supply fan motor is connected to a variable frequency drive device (VFD) to regulate its speed and thereby control-
ling the air flow. At start-up, the motor will gradually increase its speed until the desired or set CFM is met. The device
may give an output to gradually increase or decrease the speed of the motor depending on the analogue signal (0~10V)
coming from the microprocessor board. In case the supply air static pressure reaches the maximum setting, the supply
fan speed will be maintained and prevented to increase further.
4.3.2 Variable frequency drive
The VFD gives power and dictates the speed to the supply fan motor. This also eliminates the high starting current and
torque of the motor, thereby reducing the risk of nuisance circuit breaker trips at start-up.
The VFD’s (Variable Frequency Drive) settings are pre-set in the factory. The LCD display of the device is set to show the
motor speed in RPM and the drive’s output in AMPS. The on/off command is set to be controlled through switching
contacts in the main control panel of the ACU. However, the VFD can also be controlled or operated manually using its
keypad with some changes in its internal parameter settings. Please refer to the product catalogue for the setting proce-
dures.
The keypad with LCD display is attached to the unit and is used for the following:
a) Displaying the operating status of the drive
b) Displaying a fault or trip code
c) Reading and changing parameter values
d) Stopping, starting and re-setting the drive (keypad mode)
Typical Hook-Up Diagram of the Variable Frequency Drive
4.4 CONTROL PANEL DESCRIPTION AND FUNCTION
4.4.1 Main control panel
The main control panel is located beside the generator section. The panel is designed based on specifications equivalent
to a NEMA 4A enclosure. It is here where the major motor control components and the start-up control components are
fixed. The start-up control section of the panel and its component is described in the figure below:
QUICK TO CONNECT