APPLIED
POWER
SYSTEMS,
INC.
BAP1950A Three-Phase SCR Control Board
THREE PHASE SCR CONTROL AND REGULATION BOARD
Datasheet and Applications Guide
Features Include:
Automatic frequency tracking of input mains from
30Hz to 400Hz = no phase delay errors!
(Higher frequencies available on request)
Automatically corrects for phase rotation
On-board diagnostic LED indicators
Feedback for solid-state over temperature sensing of
SCR heatsink
Hard DC gate firing, suitable for firing large area
devices
The phase reference signals are filtered to reduce
harmonic content above the fundamental
On-board Feedback Control – eliminates the need for
an external controller
Improved logic implementation with state-of-the-art
FPGA
NEW - Microprocessor for increased flexibility and
improved performance
Optional on board Isolated voltage and current
feedback inputs
Industry standard size, form factor and connector
interface
NEW - Current Limit in Open Loop mode
NEW – On board pot for phase angle control in Open
Loop mode
The BAP1950A is a new release of the BAP1950.
This is a versatile three-phase bridge SCR firing board with many advanced features and functions. The
BAP1950A is the ideal firing circuit for large industrial power supplies, motor controllers and generator
controllers. It can be used to phase control AC mains; soft-start high power systems; produce variable,
unregulated DC; and with the closed loop feedback option, produce regulated DC output with voltage control
and current limiting.
The BAP1950A is insensitive to phase sequence and mains voltage distortion. It features high gate isolation
(1kV standard, higher voltages available), soft and instant start/stop functions, phase loss inhibit and can be
used at mains frequencies between 30 and 400Hz without adjustment. Its form factor and size are industry
standard and requires no additional cards to implement all of its functions and options. Power consumption is
just a few mA.
124 Charlotte Avenue Hicksville, NY 11801 Ph: 516.935.2230 Fax: 516.935.2603 Website: www.appliedps.com
Page 1 of 16
Rev. I
APPLIED
POWER
SYSTEMS,
INC.
BAP1950A Three-Phase SCR Control Board
Functional Description
Signal Conditioning of Input Reference
Controlling SCRs requires varying the phase angle
at which they turn on in order to control the portion
of the input voltage that is conducted to the output.
The BAP1950A phase locks to the input source in
order to create the references required to control the
conduction angle of SCRs in any topology.
References can be derived from the cathodes of the
three SCRs on J2, which are connected to the input
source; or from an auxiliary connector, J5. In either
case, the signals used to create the references are
filtered in order to remove unwanted harmonics that
will affect the precision with which the delay angle is
controlled.
The phase rotation of the three-phase input is
sensed and the SCR gating is automatically
adjusted to account for either ABC or ACB rotation.
Therefore, the three-phase input source cannot be
connected with an incorrect phase rotation.
However, if the auxiliary input J5 is used, the
three inputs for J5 must be consistent with the
rotation of the phases at J1 and J2. This is
explained in more detail in the connection
section on page 8.
SCR Gating Phase Locked to the Mains
Input
In order for the delay angles to control the
conduction angle of the SCRs, the delay angle must
be phase locked and then phase shifted from the
utility input by an amount determined by the delay
angle control. The BAP1950A uses a phase locked
loop circuit to keep the SCR gating signals in phase
with the three-phase input. An additional control
loop has been added that will force the delay angle
to remain constant as the input frequency varies
from 30Hz to 90Hz. 400Hz and other frequencies
are available.
Delay Angle Control (Vprog)
The magnitude of the delay angle determines the
point on the input waveform an SCR will be switched
on. This controls the output voltage of a Converter
(AC in, DC out) or an AC Controller (AC in, phasecontrolled AC out). The BAP1950A will accept a
voltage or a current that will allow the user to control
the delay angle. The output voltage is linear from 0Max signal. The Vprog signal can be inputted to J3
pin 10 OR J10 pin 2 OR a potentiometer in the J10
location.
0V or 0mA corresponds to maximum delay angle
(minimum conduction angle) or zero output
And
5V, 10V, or 20mA corresponds to minimum delay
angle (maximum conduction angle) or maximum
output.
Alternatively, a potentiometer can be installed in the
board for local control.
See options for Vprog on page 15.
In order to provide a controlled and orderly start up
sequence, the delay angle commanded by the user
is not instantly applied to the SCRs at turn-on. At
start up, the delay angle is forced to the maximum
value. When the SCR control signals are phase
locked to the input references, with no errors
present, the delay angle will ramp down from the
maximum value to the programmed value in
approximately 400mS. While in operation, the SCR
gate firing can be turned off using either the soft stop
function (shorting J3-12 to J3-11) or the fast turn off
feature (open the contact closure between J3-4 and
J3-6). When the soft stop is used, the delay angle
will ramp up to its maximum value in approximately
100mS. If the board is forced into a fast turn off
condition, all SCR gate signals will be turned off
within 1mS.
Logic Implementation
All of the logic required to perform the delay angle
control is contained on a single FPGA (Field
Programmable Gate Array).
Since it is
programmable, it can be modified to adapt to
customer needs in certain applications.
DC Gate Drive
The BAP1950A comes equipped with DC gate
drives, rather than picket fence drives, which offers
improved performance in circuits with discontinuous
load currents. If an SCR loses its holding current
when being driven with a picket fence, the SCR will
turn off and may not turn on again until it is turned
on with the higher current leading edge pulse of the
next turn on transition. The DC drive keeps current
flowing into the gate so that the SCR will continue to
be commanded on for the entire time that the SCR
can be in conduction.
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Page 2 of 16
Rev. I
APPLIED
POWER
SYSTEMS,
INC.
BAP1950A Three-Phase SCR Control Board
Fault Detection and Shut Down Sequence
The current waveform sourced to each SCR gate is
an initial 2 Amp peak pulse (rising at a rate of
approximately 1A/µS) approximately 10µS wide,
followed by 500mA of DC current for the remainder
of the turn-on signal. The open circuit voltage
applied to the gate is 24 volts, which enables the
BAP1950A to drive large area devices under high
di/dt conditions.
Options for Powering the Board
There are several options for applying power to the
BAP1950A. Transformer T2 can be driven by 120
VAC or 240 VAC via connector J4. There are
jumpers between T2 and J4 that configure the board
to accept either of these inputs. The transformer
can also be powered directly from the three-phase
source that the SCRs are controlling. By removing
J4 and installing jumpers JP8 and JP9, the voltage
at the cathodes of the phase A and phase B load-toline SCRs is connected to the primary of T2. In this
condition the turns ratio of transformer T2 is
determined by the magnitude of the input source.
In open loop mode, the delay angle is controlled
directly by the delay angle control voltage supplied
by the user at J3-10 or by adjusting a pot installed in
the J10 location. In closed loop mode, the delay
angle is controlled by the output of the voltage and
current loops. It can be turned off fast by removing
the contact closure between J3-4 and J3-6 or
ramped down slowly by shorting J3-12 to J3-11.
Either of these conditions will turn on the INHIBIT
LED.
If one or all of the input phases are lost, the PHASE
LOSS LED is illuminated and a fast turn off is
initiated which inhibits all gate signals within 1mS.
When the lost phase is restored, the unit will ramp
up to the programmed delay angle in 400mS.
If the optional temperature sensing circuit is used,
the OVERTEMP LED will be illuminated and the
gate signals are inhibited 1mS after the over
temperature threshold is exceeded. The default
value for the over temperature threshold is 90ºC.
The gate signals will ramp up to the programmed
value after the heatsink temperature drops to 85C.
This value of thermal hysteresis can be modified to
suit
the
customer’s
requirements.
DIP Switch Settings
Open Loop Mode
In Open Loop mode, the delay angle controlling
when the SCRs are fired is directly controlled by
either a voltage or current input to J3-10 or J10, or
by a pot mounted in the J10 location. When the
signal applied to J3-10 or J10 is 5V, 10V or 20mA
(also when the pot in J10 is rotated fully CW), the
delay angle is a minimum producing maximum
output voltage. When the voltage or current applied
to J3-10 or J10 is 0 (also when the pot in J10 is
rotated fully CCW), the delay angle is maximum,
1
producing a minimum output voltage.
To configure the BAP1950A as an open loop
controller, slide the leftmost switch on the dip switch
to the lower position. Depending on whether the
SCRs are configured as a converter (AC in, DC out)
or AC controller (AC in, phase controller AC out) will
determine the position of the second switch. If the
BAP1950A is not working with another BAP1950A
as a Master or Slave, then the last three switches
should be as shown in Figure 1, up down down.
1
In a converter topology that produces only positive DC output
voltage and current, the SCRs will not begin to conduct until the
voltage is ≥1.75 volts at J3-10 (there will be a deadband in the pot
as it is turned CW from fully CCW). In an AC controller topology,
the SCRs will begin to conduct when the voltage applied to J3-10
is just above 0 (or when the pot is initially rotated CW form fully
CCW).
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Page 3 of 16
Rev. I
Master
Slave
Indep/Master
Indep/Master
Slave
Indep/Slave
AC Controller
Converter
If two or more boards are connected in a
Master/Slave configuration, then the DIP switches
on each board must be set up accordingly. The
voltage loop of the Master will control its own current
loop as well as the current loop of the Slave unit.
Therefore, the DIP switches of the Master board in
Figure 10 will be set as in Figure 3 below.
Closed Loop
Slave
Indep/Master
Indep/Master
Slave
Master/Slave Configuration
Master
AC Controller
Converter
BAP1950A Three-Phase SCR Control Board
Indep/Slave
Closed Loop
Open Loop
APPLIED
POWER
SYSTEMS,
INC.
If the AC controller topology in Figure 9 is used,
simply slide the second switch from the left down to
the lower position.
Slave
Indep/Master
Indep/Master
Slave
Master
AC Controller
Converter
For the Slave board in Figure 10, configure the DIP
switch settings as in Figure 4 below.
Indep/Slave
Figure 2: Closed Loop mode converter topology
Figure 3: Master board DIP switch settings
Closed Loop
Slave
Indep/Master
Indep/Master
Slave
Master
AC Controller
Converter
Indep/Slave
Closed Loop
Open Loop
In Closed Loop mode, the delay angle is determined
by the outputs of the control loops on the
BAP1950A. A slow outer voltage loop drives a fast
inner current loop that then determines the
magnitude of the delay angle control voltage. The
DC power supplies illustrated in Figures 8 and 9
utilize the closed loop function of the BAP1950A and
require voltage and current feedback. The DIP
switch settings for the Figure 8 application should
be as indicated in Figure 2 below.
Open Loop
Closed Loop Mode
Open Loop
Figure 1: Open Loop mode DIP switch settings.
Figure 4: Slave DIP switch settings
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Page 4 of 16
Rev. I
APPLIED
POWER
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INC.
BAP1950A Three-Phase SCR Control Board
Connectors
J1
1
J2
1
JP9-2
JP8-2
J5
1
3
7
4
1
240 VAC
6
120 VAC
Slave
Independent
10
9
120 VAC
Master
Independent
Closed Loop
Independent
12
JP9-1
JP8-1
Converter
ILIMIT
Open Loop
PS OK
INHIBIT
J8
J3
Master/Slave
J11
AC Controller
J4
1
T2
OVERTEMP
PHASE LOSS
J10
J6
J12
1
6 PLACES
Figure 5: BAP1950A board layout and connector locations
Gate Drive Connectors J1 and J2
Two Mate-N-Lok™ type connectors allow for a
convenient interface with the SCR gates. The mates
for these connectors are supplied with the board
along with keying plugs to eliminate the possibility of
inadvertently swapping J1 and J2. Only one mating
connector is included if the board is to be used in a
semi converter application.
Each connector has three pairs of wires to
three SCRs. J1 is configured to drive the
upper SCRs in a converter topology or the
SCRs with the anodes connected to the utility
AC controller topology.
J2 is configured to drive the three lower SCRs in a
converter topology or the three SCRs with the
cathodes connected to the utility in an AC controller
topology. For this reason, the phase reference
signals are obtained from the J2 connector.
Therefore, if an AC controller or a semi converter is
being controlled by the BAP1950A without using J2,
J5 must be used to obtain the reference signals.
drive
three
three
in an
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Page 5 of 16
Rev. I
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INC.
J1 Connector
Pin
Signal Name
1
A+ Gate
2
A+ Cathode
3
Keying Plug
4
B+ Gate
5
B+ Cathode
6
Blank
7
C+ Gate
8
C+ Cathode
BAP1950A Three-Phase SCR Control Board
Description
Gate signal for phase A, upper SCR in converter
Reference for A+ Gate signal
Gate signal for phase B, upper SCR in converter
Reference for B+ Gate signal
Gate signal for phase C, upper SCR in converter
Reference for C+ Gate signal
J2 Connector
Pin
1
2
3
4
5
6
7
8
Signal Name
A- Gate
A- Cathode
Blank
B- Gate
B- Cathode
Keying Plug
C- Gate
C- Cathode
Description
Gate signal for phase A, lower SCR in converter
Reference for A- Gate signal; used to derive phase A reference
Gate signal for phase B, lower SCR in converter
Reference for B- Gate signal; used to derive phase B reference
Gate signal for phase C, lower SCR in converter
Reference for C- Gate signal; used to derive phase C reference
Control Signal Connector J3
The control signal connector is the BAP1950A
interface to the system controller. The table on the
following page describes the pin functions of J3.
closed loop mode and how they should be wired is
included in the DC power supply option section later
in this document.
When the BAP1950A is being used in open loop
mode with an external controller, the delay angle is
proportional to the voltage or current applied to J310. The signal applied to J3-10 can be from an
external power supply referenced to J3-8 or J3-11. It
can be obtained from a pot with one end tied to J3-7
the other tied to J3-8 or 11 and the wiper tied to J310. It can also be obtained by installing a pot in the
J10 location on the board. Regardless of how the
signal is applied, 5V, 10V or 20mA at J3-10 will result
in a minimum delay angle (maximum voltage) and 0
volts or amps will correspond to a maximum delay
angel (minimum voltage).
To enable the board, J3-4 must be pulled up to at
least 5 volts. This can be accomplished by jumpering
J3-4 to J3-6 (or J3-7) or the user can make this
connection via a relay contact to instantly inhibit the
SCR firing by opening up the contact.
When the BAP1950A is configured as a DC power
supply, J3-10 no longer controls the delay angle. By
sliding the leftmost DIP switch up to the closed loop
position, the delay angle is now controlled by the
output of the voltage and current control loops on the
BAP1950A. The rest of the pins on J3 perform the
same function in open loop or closed loop mode. An
explanation of the feedback connectors required for
The Soft Start / Soft Stop function is controlled by J312. A connection between J3-12 and J3-8 (or J3-11)
will result in a soft stop condition, which is the SCR
firing pulses ramping down to a maximum delay
angle in 100mS. When this connection is opened, a
soft start cycle will begin, which is the SCR firing
pulses ramping up to a standard minimum delay
angle in 400mS. Consult factory for options (as short
as 8mS).
The BAP1950A annunciates to the user anytime the
SCR firing pulses are inhibited by allowing J3-9 to be
pulled up to a voltage determined by the user. Under
normal running conditions, J3-9 is terminated through
a 1KΩ resistor.
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Page 6 of 16
Rev. I
APPLIED
POWER
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INC.
BAP1950A Three-Phase SCR Control Board
This Inhibit annunciate pin can be pulled high in a
phase loss condition, if J3-4 is not pulled high, an
over temperature condition, or when the BAP1950A
is not phase locked to the utility input.
Pins J3-1, 2, 3, 6, and 7 are power supplies available
to the user with limited drive capability. If the
maximum currents indicated in the table are
exceeded, damage will result on the board.
J3 Connector
Pin
1
2
3
4
Signal Name
24 VAC
24 VAC
24 VDC
Fast Turn off
5
6
7
8
Master/Slave
15 VDC
5 VDC
GND
9
Inhibit
Annunciate
10
11
Delay Angle
Control
GND
12
Soft Start/Stop
Description
From secondary winding of T2. 100mA available for customer use.
From secondary winding of T2. 100mA available for customer use.
100mA available for customer use.
Shorting this to pin 6 or 7 enables the board. Letting it float will disable gating
signals within 1mS
This pin is used when 2 or more boards are configured as Master/Slaves.
25mA available for customer use.
25mA available for customer use.
Reference for BAP1950A control circuitry including delay angle control, therefore it
must be tied to reference for delay angle control
Normally low through a 1k resistor. Transitions high in a Fast turn off (J3-4 goes
high), in an out of phase lock condition, phase loss condition or over temperature
condition
Analog input to control delay angle. 0V or 0A = Max Delay Angle;
5V,10V or 20mA = Min Delay Angle
Reference for BAP1950A control circuitry including delay angle control, therefore it
must be tied to reference for delay angle control
When it transitions from a contact closure to pin 11 to an open circuit the delay
angle ramps down from maximum to programmed value. If the board is running,
when it transitions from an open circuit to a contact closure to pin 11, the delay
angle ramps up from the programmed value to the max value.
Power Supply Connection Options J4
The necessary power supplies to run the logic on
the board and drive the SCR gates are generated
through T2. There are several options for applying
input power to T2:
1. Apply 120VAC across J4-1 and J4-5
2. Apply 240VAC across J4-1 and J4-5
3. Remove J4, connect JP8-1 to JP8-2 and
connect JP9-1 to JP9-2. The user must
indicate the voltage applied to T2, i.e. the
voltage being controlled by the SCRs, so that
the correct transformer can be installed in the
board.
4. Higher VAC input transformer available upon
request. Refer to ordering information on
page 15.
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Page 7 of 16
Rev. I
APPLIED
POWER
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INC.
BAP1950A Three-Phase SCR Control Board
J4 Connector
Pin
1
2
3
4
5
Signal Name
VAC input
Blank
Blank
Blank
VAC input
Description
AC Input to transformer T2; 120 VAC or 240 VAC
AC Input to transformer T2; 120 VAC or 240 VAC
Phase Reference Options J5
The default method of deriving references is to
sense the cathodes of the three SCRs on J2 that are
connected to the input voltage. This is a convenient
point to obtain the utility inputs, which are then
attenuated and filtered so they can be phase locked
to the delayed gate commands. The magnitude of
the utility input must be known when the board is
ordered so that the correct components are inserted
into the interface circuitry on the board.
Phase references may also be obtained by using
auxiliary connector, J5. J5 is a Mate-N-Lok™ series
connector that may be used if the circuit topology
does not allow the input voltage to be sensed via the
SCR cathodes normally available on J2. It is
important to connect J5-1 to the input phase that is
controlled by J2 pins 1 & 2, J5-3 to the input phase
that is controlled by J2 pins 4 & 5, and J5-5 to the
input phase controlled by J2 pins 7 & 8 (see Figure
3).
J5 Connector
Pin
1
3
5
Signal Name
Phase A Reference
Phase B Reference
Phase C Reference
Description
Reference input for phase controlled by gate drives on J1/J2 pins 1 & 2
Reference input for phase controlled by gate drives on J1/J2 pins 4 & 5
Reference input for phase controlled by gate drives on J1/J2 pins 7 & 8
High Voltage Feedback J6
If the closed loop option is ordered, the DC output of
the power supply is brought back to the board via
J6. An isolation amplifier on the BAP1950A board
attenuates the high voltage and isolates it from the
output so that the feedback can be referenced to the
signal ground.
J6 Connector
Pin
1
2
3
Signal Name
Output Voltage
Blank
Output Reference
Description
DC output voltage up to 1000V; tied to the cathodes of upper SCRs, or after
filter in a converter topology
DC output reference; tied to the anodes of the lower SCRs in a converter
topology
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Page 8 of 16
Rev. I
APPLIED
POWER
SYSTEMS,
INC.
BAP1950A Three-Phase SCR Control Board
Current Limit Control J8
The value of current at which the power supply will
fold back can be adjusted with a remote pot
connected to J8 or on-board pot installed in the J8
location. A 10 kΩ pot should be used in this
application.
The BAP1950A allows the user to incorporate this
feature in open loop or closed loop modes. Current
feedback provided at J11 by an open loop Hall
Effect sensor and a current limit controlling pot
installed locally or remotely at J8 is all that is
required.
Rotating J8 to the fully CW position will result in
maximum output current, determined by the size of
the Hall Effect Sensor and resistor scaling on the
BAP1950A. Rotating the pot in the CCW will reduce
the amount of current output from the SCRs. This
feature allows the BAP1950A to operate as a current
source in open or closed loop mode. J3-10 must be
tied to J3-7 when operating as a current source.
If desired, the pot can be removed and the current
can be controlled by an input voltage of -5VDC to
OVDC on pin 2.
J8 Connector
Pin
1
2
3
Signal Name
High Side
Pot Wiper
GND
Description
Connected to the high side of the pot
Connected to the wiper of an external 10K pot
Connected to the low side of the pot
Remote Voltage Control J10
The output voltage of the power supply can be
controlled remotely with an external pot (the
minimum pot used in this application should be a
1K) or a 0 to 5V signal. This connector can be
replaced with a board mounted 10K pot to control
the power supply output voltage, or the phase angle
in open loop mode. The 5V reference at J10-1 has
a limited source capability of 10 mA. Therefore, it
should not be used for any circuitry other than the
pot.
J10 Connector
Pin
1
Signal Name
5V Reference
2
Pot Wiper
3
GND
Description
Precision 5V reference created on board used to control output voltage; limited to 10
mA. Connected to the high side of the pot.
Connected to the wiper of an external pot. This pin can also be driven by a remote
voltage source referenced to pin 3, where 0V is 0V on the output and 5V is the fullscale output.
GND; Connected to the low side of the pot
Current Feedback J11
The BAP1950A provides a connectorized interface
to an open loop current transducer for current
feedback to be used for an inner current loop and/or
current limiting. The inner current loop enhances
system performance by improving stability and
allowing the user to set or vary a current limit. The 4
pin header on the board interfaces directly with the
HAS and HAX open loop hall effect sensors from
LEM, providing an inexpensive means for obtaining
accurate current feedback.
The LEM current transducer can be placed on either
side of the load. All diagrams show the current
transducer on the positive load side, with the
appropriate the current flow (arrow). If the current
transducer is required on the negative side of the
load, to eliminate floating the current transducer in
high voltage supplies, for example, the current flow
is reversed (arrow points away from the load).
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Page 9 of 16
Rev. I
APPLIED
POWER
SYSTEMS,
INC.
BAP1950A Three-Phase SCR Control Board
J11 Connector
Pin
1
2
3
4
Signal Name
15 VDC
-15 VDC
Current Feedback
GND
Description
15 VDC
-15 VDC
Voltage proportional to the current sensed
GND
Temperature Sense J12 (optional)
A temperature sensor can be used to interface with
the board via J12. The temperature sensor can be
mounted on a heatsink to prevent the SCRs from
operating at a temperature beyond their ratings. A
threshold can be set on the board, so that when
the temperature is exceeded, the BAP1950A will
inhibit SCR gating and illuminate the OVERTEMP
LED. The temperature sensor should be mounted
near the hottest point of the heatsink.
APS
temperature sensor part number BAP2161A-3 is
available as an option.
J12 Connector
Pin
1
2
3
Signal Name
15 VDC
Temp
GND
Description
15 VDC
Analog voltage proportional to temperature
GND
APPLICATIONS
The following will provide the user with an explanation of how the BAP1950A controls SCRs in several
common applications, basic DC converter, regulated DC converter and AC Controller. These are the most
common circuit topologies found in industry. Included is a functional description of the circuitry and
instructions for connecting the BAP1950A in a system.
DC Power Supply – Full Control Converter
firing the SCRs is accessed via J3. See the J3
connector description on pages 6 and 7.
The basic design of an SCR three-phase bridge
power supply is shown in Figure 6 on page 11. This
is called a full converter, converting 3-phase AC into
DC.
Connections to the BAP1950A board are
shown. The SCRs are connected to the BAP1950A
with connectors J1 and J2. The customer control
signals used to control the phase angle delay for
When the BAP1950A is configured as an open loop
AC to DC converter, see Figure 6, the phase angle
delay is determined by the voltage or current applied
to J3-10. The DIP switch is set to the positions
indicated in Figure 1. The other connections on J3
are used as needed.
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Page 10 of 16
Rev. I
APPLIED
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INC.
BAP1950A Three-Phase SCR Control Board
Slave
Indep/Master
J1
8
Master
Customer
Control
Interface
5 7
Indep/Slave
J2
2 4
Indep/Master
1
Slave
8
AC Controller
5 7
Converter
2 4
Closed Loop
1
Open Loop
LOAD
AP-1950
BAP1950A
J3
Figure 6: Full Converter connection
DC Power Supply - Half Control Converter
The default means of deriving references, in a full
control converter topology, is to sense the cathodes
of the three SCRs on J2 that are connected to the
input voltage.
However, in a half-control
configuration as shown in Figure 7, rectifiers replace
the SCRs and no reference is available.
Phase references may be obtained by using auxiliary
TM
connector, J5.
J5 is a Mate-N-Lok
series
connector that may be used if the circuit topology
does not allow the input voltage to be sensed via the
SCR cathodes normally available on J2.
It is
important to connect J5-1 to the input phase that is
controlled by J1 pins 1 & 2, J5-3 to the input phase
that is controlled by J1 pins 4 & 5, and J5-5 to the
input phase controlled by J1 pins 7 & 8 (see Figure 7
on the following page).
Regulated DC Power Supply
Designing a regulated DC power supply requires
setting the DIP switch settings to those indicated in
Figure 2 and installing the isolation amplifier circuitry
on the board. This allows the design of a DC voltage
regulation loop with an adjustable current limit as well
as an inner current loop for stability. Information
must be provided to APS when ordering, regarding
the system’s output filter and required step response
so that error amplifier compensation components can
be selected. Computer simulations of the system’s
dynamic performance can be performed at APS to
determine the compensation components that will
optimize system response and ensure stability. With
this information, one can use the BAP1950A board in
the circuit configurations shown in Figures 8 and 9.
Figure 8 is the most common circuit used for
regulated power supplies. The BAP1950A board has
the optional isolation amplifier and compensating
components installed. In addition, a Hall Effect
124 Charlotte Avenue Hicksville, NY 11801 Ph: 516.935.2230 Fax: 516.935.2603 Website: www.appliedps.com
Page 11 of 16
Rev. I
APPLIED
POWER
SYSTEMS,
INC.
BAP1950A Three-Phase SCR Control Board
current transducer is employed for current feedback
to the BAP1950A.
In order to optimize the
performance of the system, the user must inform
APS of the filter (capacitor and inductor) values. This
will allow us to install the proper values of
compensating components to insure proper
operation, stability and response.
Figure 9 is another common circuit employed for
regulated DC power supplies. This topology is used
when the output voltage is higher than 600V to 1kV
rms. The advantage of this topology is that the
mains voltage is usually below 600V rms and SCRs
with blocking voltages below 2kV can be used. It is
usually easier to put rectifiers in series strings than it
is to put SCRs in series. In addition, the current
rating of the input mains SCRs is usually lower than
they would be in the transformer secondary circuit.
Depending on the specifics, the SCR and rectifier
total costs may be lower with the circuit topology in
Figure 9 than the circuit topology in Figure 8.
Master
Slave
Indep/Slave
Indep/Master
J3
8
Indep/Master
J5
Customer
Control
Interface
5 7
2 4
Slave
1
AC Controller
5
Converter
3
Closed Loop
1
Open Loop
LOAD
J1
BAP1950
AP-1950
A
Figure 7:than
Sensing
voltage
with auxiliary connector J5 to obtain phase reference, with half-control topology.
Higher
Six input
Pulse
Operation
Higher than Six Pulse Operation
If 12 pulse open loop regulation is required, one
BAP3012 Controller may be used. If 18 pulse or
higher is required, then several BAP1950A boards
may be set up in a Master / Slave configuration. The
Master board will have the DIP switch settings as
indicated in Figure 3 and the slave boards will have
the DIP switch settings as shown in Figure 4. The
output of the voltage error amplifier of the master
board will be exported out to J3-5 and it will
be imported on J3-5 of the slave boards. This
voltage error signal will be the input to the current
loop for the master as well as the slaves. The output
of the current loops will determine the conduction
angle of the SCRs. A DC power supply with a 12pulse rectifier using two BAP1950As in a
master/slave configuration is illustrated in Figure 10.
124 Charlotte Avenue Hicksville, NY 11801 Ph: 516.935.2230 Fax: 516.935.2603 Website: www.appliedps.com
Page 12 of 16
Rev. I
APPLIED
POWER
SYSTEMS,
INC.
BAP1950A Three-Phase SCR Control Board
Hall Effect
Current
Sensor
ISOLATION
TRANSFORMER
LOAD
Slave
Master
AC Controller
Indep/Master
Closed Loop
1:X
4
2 4
5 7
8
1
2 4
5 7
8
J1
J2
Indep/Master
Indep/Slave
Slave
Converter
Open Loop
1
J11
AP6PGFB
BAP1950A
Customer
Control
Interface
J3
1
J6
3
Figure 8: Basic regulated DC power supply using the closed loop option of the BAP1950A board.
Hall Effect
Current
Sensor
Isolation
XFMR
LOAD
1
2 4
5 7
8
1
2 4
J2
5 7
8
J1
J11
Customer
Control
Interface
AP-1950
BAP1950A
J3
J6
Figure 9: DC regulated power supply using AC Controller topology
124 Charlotte Avenue Hicksville, NY 11801 Ph: 516.935.2230 Fax: 516.935.2603 Website: www.appliedps.com
Page 13 of 16
Rev. I
APPLIED
POWER
SYSTEMS,
INC.
Figure 6:
BAP1950A Three-Phase SCR Control Board
Example of 12-pulse operation using two BAP1950A boards, one configured as a Master the
Hall Effect
other as a Slave.
Current
Sensor
ISOLATION
TRANSFORMER
LOAD
DELTA
Slave
4
Master
AC Controller
Indep/Master
Closed Loop
SECONDARY
1
2 4
5 7
8
1
2 4
5 7
8
J1
J2
Indep/Slave
Indep/Master
Slave
Converter
Open Loop
J11
AP-1950
BAP1950A
Customer
Control
Interface
J3
1
J6
3
MASTER
Hall Effect
Current
Sensor
ISOLATION
TRANSFORMER
WYE
Slave
Master
AC Controller
Indep/Master
Closed Loop
SECONDARY
4
Indep/Master
Indep/Slave
Slave
Converter
Open Loop
1
2 4
5 7
8
1
2 4
5 7
8
J1
J2
J11
BAP1950A
AP-1950
Customer
Control
Interface
J3
SLAVE
Figure 10: DC regulated power supply with paralleled converters using Master/Slave configuration
(Note: If closed loop control is not required, one BAP3012 controller may be used in place of the two
BAP1950A controllers)
124 Charlotte Avenue Hicksville, NY 11801 Ph: 516.935.2230 Fax: 516.935.2603 Website: www.appliedps.com
Page 14 of 16
Rev. I
APPLIED
POWER
SYSTEMS,
INC.
BAP1950A Three-Phase SCR Control Board
Ordering Information:
BAP1950A-X-XX-X-X-X-X-X-XX
Feedback
OL – Without Current / Voltage Feedback
CL – With Current / Voltage Feedback2
Mains Frequency (Hz) – 4 - 400
5 - 50
6 - 60
Vprog
1 – 0 10V
Temperature Sense
4 – 4 20mA
T – Temperature Sense3
5 – 0 5V
0 – No Temperature Sense
P – Onboard Pot. in J10 location
H – 3 pin header for remote Pot.
Voltage Controlled by SCRs
1 – 10 100 VAC
2 – 100 690 VAC
3 – High Voltage (consult factory for options)
Phase Reference
K – Cathodes sensed on J2* (*Default setting)
A – Auxiliary connector J5 (must use with “A” circuit topology)
Input Power Supply
02 – 24 VAC on J3 connector
12 – 120 VAC on J4 connector
24 – 240 VAC on J4 Connector
20 – 208 VAC from phase A and B cathodes on J2*
38 – 380 VAC from phase A and B cathodes on J2*
46 – 460 VAC from phase A and B cathodes on J2*
*not available with 400Hz
Circuit Topology
C – Full Converter
A – Semi Converter Diodes Low
B – Semi Converter Diodes High
R – AC Controller
S – Star Converter
A complete part number, as well as the information requested on the last page must be submitted when
requesting a quote or placing an order.
2
Closed loop option requires the following information:
1. Full scale output voltage (1kVdc max.)
2. Maximum output current
3. Current sensor being used (mfg. and part number)
4. How will output voltage and current limits be controlled?
a. If using potentiometers, are they to be on-board or off-board?
b. If providing voltages, what is full-scale voltage?
3
Consult factory for Over Temperature threshold settings – heatsink Over Temperature set-point can be set
between 40C and 100C. BAP2161A-3 Temp Sensor is available as an option for mounting on heatsink.
124 Charlotte Avenue Hicksville, NY 11801 Ph: 516.935.2230 Fax: 516.935.2603 Website: www.appliedps.com
Page 15 of 16
Rev. I
APPLIED
POWER
SYSTEMS,
INC.
BAP1950A Three-Phase SCR Control Board
Additional information required for BAP1950A Ordering
Full Part Number of the board you are ordering:
BAP1950A-__________________________________________________
What is full scale output voltage?
What is the full scale output current?
If ordering a Closed Loop version (-CL), what Hall Effect current
sensor is being used? NOTE: the BAP1950 only supports open
loop Hall Effect current sensors such as the LEM HAS series.
Do you prefer on-board potentiometers, off-board pots (board
will be supplied w/ 3 pin headers) or a signal voltage to control
Vprog and Ilimit? If signal voltage, refer to selection at the end of
the part number.
What is the type of load? (ie: resistive, inductive, other)
Please supply this information with your order or RFQ as well as any other details specific to
the application.
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