AP903AP - SixPac™ Series of SCR AC Controller and DC Converters

Complete Series of SCR Three-Phase Power Control Units

Compact, rugged construction
Applications include:
  Windmill Converters
Motor Starters
Motor Drives
Phase Control AC
Regulated DC Power Supplies
Variable Output Voltage
Output Ratings:
  AC to 500Arms
DC to 600ADC
10 to 750VAC Input Voltage
40HZ to 80Hz Input Tracking with No Tuning
  Filter Capacitor Bank
Input Fusing
Laminated Bus
Snubber Board
Current Sense
Forced Air Cooling

The APS SixPac™ Series of power controllers are built on a rugged, compact, all-inclusive, economical base They have a great deal of flexibility to provide OEMs with a fully functional set of power stages They have been designed for long life in heavy-duty industrial applications The SixPac™ includes three dual isolated SCR modules that can be configured as either a three-phase AC Controller (AC in, phase-controlled AC out) or a regulated DC Converter (AC in, regulated DC out) This versatile power stage can be applied to virtually any power application that needs phase controlled AC or regulated DC and includes solid-state motor starters, soft-start/soft-stop, variable speed drives, windmill alternator converters and regulated power supplies to name a few.

The isolated SCR modules are mounted on a high efficiency heatsink with input fusing, forced air cooling, and a capacitor filter bank (for regulated DC output) A snubber for the SCRs is available if dv/dt limiting is required The compact design of our standard system measures approximately 18” wide by 10” long by 11” high, including the cooling fan, fuses, Hall effect transducer, output bus, snubber board, SCR gate drive board, capacitor bank, etc.

The SixPac™ is available with input from 10VAC to 700VAC, input frequencies from 40 Hz to 80Hz without tuning (this means that input from variable frequency alternators is acceptable as long as the frequency is within limits) AC Controller output currents range from 50ARMS to over 500ARMS Regulated Converter outputs range from 100ADC to over 600ADC

All units come with our industry proven AP-1950 SCR Gate Firing Board The AP-1950 board is a flexible three-phase SCR controller suited for industrial/commercial power supplies of any power level It utilizes advanced FPGA control logic to increase reliability, circuit flexibility and reduce circuit component count The AP-1950 is designed to keep the programmed delay angle constant over a wide input frequency range (40Hz to 80Hz) This universal input feature does not require tuning in applications where the input mains frequency may vary, as in motor generator sets, windmill power generating equipment, and all field generating systems The three-phase mains input is filtered by a unique signaling processing circuit that is not sensitive to harmonic distortion, input voltage amplitude fluctuations, frequency variations or phase sequence.


The SixPac™ configured as an AC-DC Converter, as in Figure 1, has the following features

Phase Reference Sensing & Frequency Tracking

An on board low pass filter is used to greatly reduce the harmonic content of the mains input used to generate the reference signals. The low pass filter attenuates the fifth harmonics above 60Hz, reducing delay angle errors from input line distortion. Additional circuitry actively forces the programmed delay angle to remain invariant over a mains input frequency from 40Hz to 80Hz. Therefore, operation of the SixPac™ in applications where frequency fluctuations occur regularly, i.e. when running from an alternator input powered by a diesel, gasoline or turbine engine; or when running from a system with an un-stabilized frequency is permissible. The programmed delay angle will remain constant over the frequency range from 40Hz to 80Hz with an accuracy of ±0.25º.

Closed Loop Voltage Regulation

The SixPac™, when supplied as a DC Converter, is equipped with circuitry to provide a regulated DC output, with adjustable voltage and current limits. The output is determined by a voltage reference that can be obtained from either an off board reference, the on board pot or an off board pot. The voltage reference is compared via an error amplifier to output voltage feedback that is processed through an isolation amplifier. Current feedback is brought back to the board via a connector (J11) that interfaces with an industry standard Hall Effect current transducer. An example of such an application is shown in Figure 1. Consult factory for output voltage scaling and error amplifier compensation networks to obtain the desired transient response and stability.

Soft-Start /Stop

This circuit overrides the gate delay angle command. It is enabled by the power-on-reset feature or by contact closure inputs. SCR gating begins at the maximum delay angle limit and ramps down to the commanded delay angle at a rate determined by the soft-start time constant. The Soft-Stop feature, when activated by a contact closure, causes the SCR gate delay angle to ramp up from the command angle to the maximum delay angle limit before SCR gating is inhibited.

Fast Turn-off

SCR gating is quickly enabled or inhibited (~20µSec) on contact closure input.

Phase Loss Inhibit

The phase loss circuit inhibits the SCR gate drive if a loss of phase voltage is detected. When voltage is restored, the soft-start circuit is engaged.

Overtemperature Inhibit

SCR gating is instantaneously inhibited in an over temperature condition.

Gate Delay Transfer Function

The gate delay is determined by a phase locked loop consisting of a summing junction, low pass filter, voltage-controlled oscillator and an application specific integrated circuit. The voltage-controlled oscillator frequency is locked to the mains frequency. The DC control voltage is inserted into the summing junction to set the SCR delay angle.

The SCR gate delay angle is controlled by an input signal between 0 and +5 VDC. Gate delay angle is inversely proportional to this input signal. Minimum and maximum delay angles are determined for a given application and the proper offset resistor is selected from the provided resistor network.

DC Gate Drive

The SixPac™ drives each SCR with direct current. The firing signal is an initial 2Amp pulse with a 500mA current for the duration of the conduction angle. The open circuit voltage is 24 Volts DC. This gate drive is suitable for driving large area SCRs in high di/dt applications.

Remote Voltage Control

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 an on board 10K pot to control the power supply output voltage. 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 Signal Name Description
1 5V Reference Precision 5V reference created on board used to control output voltage; limited to 10 mA. Connected to the high side of the pot.
2 Pot Wiper 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 full-scale output.
3 GND GND; Connected to the low side of the pot

Current Limit Control

The DC output of the power supply is brought back to the board via J6. An isolation amplifier attenuates the high voltage and isolates it from the output so that the feedback can be referenced to the signal ground.

J8 Connector
Pin Signal Name Description
1 High Side To external high side of pot
2 Pot Wiper To external pot wiper (10kΩ)
3 GND To external pot low side

SixPacâ„¢ as an AC to DC Converter with regulation
Figure 1: SixPac™ as an AC to DC Converter with regulation (voltage and current feedback)

TB1 Connector Customer Interface for an AC to DC Converter AC to AC Controller Applications
Pin Pin Function Description
1 120V/208V AC From J4 on AP-1950 board
2 120V/208V AC From J4 on AP-1950 board
3 N/C Not Used
4 Fast Turn-off Shorting this pin to pin 10 enables the power supply.  Letting this pin float will disable the power supply within 20µSec.
5 Soft Start/Stop When opened from GND (pin 6 or 9), the delay angle ramps down from maximum to the preprogrammed value.  If supply is running when the pin is shorted (to pin 6 or 9), the delay angle ramps up from the programmed value to the maximum value.
6 GND Reference for AP-1950 control circuitry including delay angle control, therefore it must be tied to reference for delay angle control
7 Inhibit Enunciate Normally low through a 1k resistor.  Transitions high in a Fast turn off or in an out of phase lock condition.
8 Delay Angle Control 0 to 5 V analog input to control delay angle, when operating in OPEN LOOP mode.  0V ® Max Delay Angle; 5V® Min Delay Angle
9 GND Reference for AP-1950 control circuitry including delay angle control, therefore it must be tied to reference for delay angle control
10 +5V DC Up to 50mA for customer use

Figure 1

Figure 2

Figure 3
Figure 3: Mechanical configuration for the DC Converter rated at 400A output at 40°C ambient.

Output Current Ratings
SixPac™ Size AC Controller DC Converter
Load (Amps) Fuse Rating Load (Amps) Fuse Rating
60 50 60 100 100
90 75 90 150 150
150 150 175 300 300
250 300 350 400 400


High Power Inverters

High Power Inverters

5-500 kilowatt Inverters, AC Controllers and IGBT Inverters are available with Full Bridge, Half Bridge, 3-Phase Bridge, Chopper and Soft Start Circuits.  Options include Air or Liquid Cooled, Voltage Feedback, Current Feedback, Thermal Feedback, Snubbers,  Laminated Bus, DC Filter Capacitors, Fuses, and Blowers/Fans. Our Single Phase or 3-Phase Inverters are designed to fit a wide range of applications or custom designed to fit uniqe requirments.

High Power Converters

High Power Converters

Our High Power Converters are available in Single Phase, Three Phase, Poly Phase, AC Switch, Parallel Configuration and Static Switch configurations.  Options include Air or Liquid Cooled, Voltage Feedback, Current Feedback, Thermal Feedback, Snubbers, Laminated Bus, Filter Capacitors, Output Bus Bars, and Blowers/Fans.  These products are widely used for High-Power Motor Control, High-Power AC-DC Power Suppplies and High-Power DC-DC Power Supplies.

High Power Semiconductor Assemblies

High-Power Semiconductor Assemblies

Our High-Power Semiconductor Assemblies are available with Single, Doubler, Three Phase, Full Bridge, Series Stacks, Parallel, AC Switch, Static Switch, Common Anode/Common Cathode Topologies.  Options for include Air or Liquid Cooled, Bus Bars, Gate Firing Boards, Fuses, Snubbers, Blowers/Fans, Thermal Switches, Insulated Mounting and FiberOptic Interfaces. We offer a wide range of Power Semiconductors to satisfy a wide range of power management requirements.


IGBT and SCR Gate Driver Boards

IGBT and SCR Gate Driver Boards

Our IGBT and SCR Gate Driver Boards come in Full Bridge, Half Bridge, 3-Phase Bridge, Single, Doubler, Twelve Pulse, AC Switch and High Voltage Driver circuit boards.  Options for our IGBT and SCR Converters include Voltage Feedback, Current Feedback, Thermal Feedback, Device Fault Protection, Circuit Protection and FiberOptic Interface.  Our SCR and IGBT Controllers are made to fit a wide range of applications and can be quickly customized to meet unique applications.

Custom High Power Systems

Custom High Power Systems

We offer Custom High Power Systems design utilizing our years of experience with power component technologies.  We we can design build entire high power system with state of the art enclosures, digital / analog interface signals, control and monitoring circuitry.  Our advanced cooling techniques with baseplates, heatsinks, fans, blowers and liquid cooling devices ensure your custom power supply design will have the best in thermal management.