I was called in to help trouble shoot a control system console that had noise issues. It turned out to be the triple redundant power supplies. Each power supply goes through a diode before being tied together to power seven cabinets. The power supplies are Phoenix Quint 40 Amp supplies and the diodes are rated for 50 Amps. With one power supply powered up, there are no noise issues. As soon as I power up another power supply, the noise issues start. It doesn't matter which power supply is used, the same thing happens when a second is brought up. It is worse with all three power supplies powered up.
Where I saw the noise was on some simulation equipment that is connected to simulate the I/O. The valve commands go to a comparator and the output of the comparator is five volts with frequent noise spikes going to zero volts. I don't see the noise on my scope (200 Mhz). The active signal to the comparator is a 24 VDC PLC output. There is a 10 K Ohm pull-down resistor on the comparator input for when the PLC output is off.
Any suggestions??? I need to get the system to operate with all three power supplies working.
Where I saw the noise was on some simulation equipment that is connected to simulate the I/O. The valve commands go to a comparator and the output of the comparator is five volts with frequent noise spikes going to zero volts. I don't see the noise on my scope (200 Mhz). The active signal to the comparator is a 24 VDC PLC output. There is a 10 K Ohm pull-down resistor on the comparator input for when the PLC output is off.
Any suggestions??? I need to get the system to operate with all three power supplies working.
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