XLT XD-9006A (GAS Oven Version – C, AVI Hood Version – B) - Manual (Page 9)

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GAS OVEN THEORY OF OPERATION
BC - The Burner Control (BC) is powered by 24 VAC from the Transformer (XFMR). Incoming
power will be interrupted by the Temperature Control (TC) when the actual temperature rises
above the Maximum Operating Temperature (see Specification Sheet). When the BC receives
power, it initiates a pre-purge lighting sequence. A red LED will blink once after about 2-3 sec-
onds to give notification that the lighting sequence has started. After about 30 seconds, two events
occur; 1) a high-voltage electrical signal will be sent to the Flame Sensor/Spark Igniter (FS/SI)
from the Spark Terminal, and 2) a 24 VAC signal will be generated across Terminals V1 & V2.
The high voltage jumps across a gap in the FS/SI creating a spark that can be heard, although the
BC only produces this spark for four (4) seconds. One end of the Rectifier Plug is connected to
Terminals V1 & V2 through a Circuit Breaker (CB6). The Rectifier Plug rectifies the 24 VAC to
24 VDC. The other end of the Rectifier Plug is connected to Terminals 1 & 4 of the Main Valve
(V1-V2). The V1-V2 valve will open, allowing fuel to flow into the burner. When the two simul-
taneous events occur, fuel flow and spark, ignition should occur. When flame is sensed by the FS/
SI, a DC current is sent to Terminal S1 of the BC. The BC uses this DC current to prove ignition.
A minimum of .7 µA is required to maintain operation. If the Burner lights, the LED will not
flash. If the Burner fails to light, the LED will flash three (3) times, repeatedly, and the BC will
not attempt to re-light.
CAP - The Capacitor is physically mounted inside the Control Box but wired to the externally
mounted Main Motor. The Main Motor is a permanent split capacitor (PSC) motor. PSC means a
capacitor motor in which the starting capacitor and the auxiliary winding remain in the circuit for
both starting and running.
CB - Circuit Breakers are used to protect electrical components. The current value is printed on
the front of all breakers. If a CB is tripped, eliminate the cause and press the front to reset.
CC - The Conveyor Control is supplied 24 VDC by the Power Supply (PS) via a Circuit Breaker
(CB3 & CB4, optional) to Terminals #4 & 5. The belt time is displayed, and is user-adjusted by
pressing and holding the up or down arrow button switches. See the Specification Sheet for mini-
mum and maximum belt times. The motor speed is calculated based on the time that is entered.
This time is translated to a RPM on the motor shaft depending on the size of the oven, the diameter
of the sprocket, and the gear ratio of the gearbox. Once the motor is running, hall sensor inputs are
fed back into the driver to determine the speed the motor is currently running at. This input goes
into a PID algorithm to adjust the PWM output to control the speed to match the target speed that
was calculated first. This PWM is adjusting the average voltage that the motor phases are seeing.
As the average voltage goes up, the motor will speed up. As the average voltage drops, the motor
speed will also drop. The maximum speed is based on a continuous 18-24V being supplied to the
motor. The phasing of the controller is dependent on the hall sensor signals that are being re-
turned. The controller reads the hall sensor position and from there knows which phase of the mo-
tor receives the 18-24V signal, which phase of the motor is the return and which phase of the mo-
tor is left open. As the motor spins, the hall sensors change, which dictate which phases are ener-
gized.