Watlow VPAC-BT User Manual
General Description
The BT card (Watlow P/N 08-5406) is time proportioning
with a variable (very fast) time base. At 50% power, one
full cycle is ON, and one full cycle is OFF. At 25%
power, it is ON one cycle and OFF for three. At 90%, it
is ON nine cycles and OFF for one. As the command
signal gets farther from 50% power, the time base gets
longer. The maximum time base resolution is 1 in 360
ac cycles. The BT card is factory set for 4-20mA into
250Ω. It can be changed to a voltage input by removing
the 300Ω, R22 resistor, located on the lower right corner
of the card. Without R22, it is a 5K input impedance.
See the illustration on the reverse side. Bias and gain
pots allow the card to be adjusted for any voltage from
0-3VÎ (dc) to 15VÎ (dc) or current between 0 to 25mA.
BT card power supply requirements are 24VÅ (ac) center tap transformer secondary. Transformer primary
must be connected to the same line phase as the heater
load. For example, is the heater is powered by L1 and
L2, then the power transformer must also be connected
to L1 and L2. See the illustration on the reverse side.
Dimensions
Specifications (1276)
Input
• Process input factory set @ 4-20mA Î (dc)
• Input impedance 250Ω (clip resistor for 5KΩ voltage
input), or manual control input
Output
• Burst firing control, variable time base
• TTL compatible (5V logic) at about 5mA @ 5V. Will
drive one industry standard 3-32VÎ (dc) input random fire SSR. For single phase only.
Line Voltage Power
• 50/60 Hz V~ (ac) line frequency
• Voltage ±10%, 120, 208, 240, 277, 380, 415, 480V~
(ac). Power transformer is supplied with the BT
card. When ordering, specify power supply voltage
and line frequency.
Line Voltage Compensation
• 10%∆ in line, 2%∆ in load in the 30% to 70% power
region.
Input to Output Linearity
• 2%, 30% to 70% power region
Operating Environment
• 32 to 122°F (0 to 50°C)
Storage Temperature
• -40 to 185°F (-40 to 85°C)
Options
• Manual control kit for voltage input cards (1KΩ
potentiometer) #08-5362. Includes dial, knob, 1KΩ
pot and wiring.
Ordering Information
• Watlow P/N 08-5406
2.5"
(64 mm)
2.5"
(64 mm)
3.0"
(76 mm)
Input
+
_
Bias
Gain
To VÎ (dc)
Input SSR
08-5406
R22
Watlow Controls
1241 Bundy Blvd., P.O. Box 5580
Winona, MN 55987-5580
Phone: 507-454-5300, Fax: 507-452-4507
VPAC-BT
Remote Mount Transformer
Data Sheet
0600-0028-0002 Rev C (1277) Made in the U.S.A.
January, 1998 Printed on Recycled Paper
10% Postconsumer Waste
Input
Pot (+) (-)
Transformer Plug
R22
Zero Cross
SSR
- +
BT
8
7
6
5
4
3
2
1
4
3
2
1
Heater
Safety Contactor
if required
Semiconductor
Fuse
Branch Circuit
Fuses
Transformer
Fuses
Primary
Transformer
Connections
(bottom view)
red
black
white
black
240
Volt
120
Volt
Secondary
Transformer
Connections
(top view)
Note:
Input is 250 ohms.
For 5K input, cut R22.
Common
Positive
Pot (+) (-)
Manual Control
L1
L2
12V~(ac)
Common
(center tap)
12V~(ac)
orange
white
violet
Note:
The controls transformer must
be on the same phase as the
load. See wiring diagram. All
hot lines to the transformer
should be fused at 1 amp with
the proper line voltage.
For manual control, a 1KΩ
potentiometer may be connected
to the AT card input terminals.
Watlow offers a Manual Control
Kit, P/N 08-5362. Using this
potentiometer requires removing
the 5KΩ, R2 resistor for higher
impedance.
Bias and gain adjustment is
required when changing from 4-
20mA input to a manual control
input or a voltage input.
Wiring Diagram for VPAC-BT
Remote Mount Transformer
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