ACB-3000, 2 Milliseconds Switching When One Line Fails

Find out in this article the performance of Premium PSU’s ACB-3000 redundancy static transfer switch.

We have recently carried out tests on the ACB-3000 that prove that the device switches in less than 2 milliseconds from one input to the other in an error situation.

What Is an ACB-3000?

The ACB-3000 is an ultrafast two lines static transfer switch. It selects the appropriate line in case one of them fails.

PSU ACB-3000

The device constantly monitors the evolution of the waveform of both lines. If the selected line goes out of the specifications, the system changes the line in less than 2 milliseconds, which is possible due to its fully digital control and the power switches used: SiC MOS.

The ACB-3000 is suitable for the Premium PSU’s ODS-750ODS-1500 and ODS-3000 inverter families, which have been designed to operate in both industrial and railway environments.

In case of failures, the unit can signal locally using a LED, and also remotely by a solid-state signalling relay and a CANopen bus port. The ACB-3000 is also protected against overloads and short circuits through a current-limiting circuit.

How Did We Carry Out the Testing?

We used two ODS-3000 for the measurement and exposed them to different situations to cover as many scenarios as possible.

We also used:

  • A Tektronic TBD 2000 oscilloscope, calibrated at 21/01/2020
  • A Xantrex XDC 60-100 as the source that supplies the ODS
  • An ElektroAutomatik EA-PS 5200 10A used as a second DC source to supply the remote control of the ODS

All tests were carried out in a full load situation.

PSU Testing set upImage 1: Testing set up

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What Were the Results?

Image 2 shows the SiC Mosfet drivers’ signal difference between the deactivation of the first one and the activation of the second one is exactly 2 ms. Since the microcontroller detects an error from the first line, it takes 2 ms to check the other input and decides if it can switch to the other line.

PSU SiC Mosfet drivers’ signal differenceImage 2: Gate signal of channel 2: yellow – Gate signal of channel 1: blue

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Image 3 shows the output signal of the ACB in a switching situation. In this case, we supplied both inputs with the same ODS to ensure the inputs were in phase. To force an error situation, we used a simple circuit breaker in priority input.

PSU output signal of the ACB in a switching situationImage 3: Output signal in a switching situation when input signals are in phase

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Image 4 shows switching operations when lines aren’t synchronized.

PSU static transfer switch Testing Image 4Image 4: Output signal in a normal switching situation, where input lines are not in phase

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The ACB-3000 can detect different types of defects in line and switch to the other in less than 2 ms, a priceless amount of time for most of the loads. During the 2 ms, the unit samples both lines, processes the data and decides changing or not the input line. In case of a line failure, the present strategy is to apply a blanking during the 2 ms at the output to avoid unknown transients.

At Premium PSU, we are currently working on improving the ACB-3000’s switching alogrithm in order to reduce the  switching time or eliminate the blanking time.

This article was originally published by Premium Power Supplies.