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.

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.

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