Phoenix Power supply unit hissing sound

Vivek_PV · Jan 9, 2019

Hello All,

We are using two "QUINT-PS/1AC/24DC/20 - 2866776" Power supplies for one of our project. The input power is single phase 240V and out power is 24VDC which is used to drive PLC CPUs, I/O Racks, and solenoid valve relays.
There is some kind of hissing sound coming from the Power supplies when turned ON. The total estimated load is 16.39 Amps and 430 watts.
The two power supplies are for redundancy.
Is there any specific reason behind this behaviour?
Please help

Regards
Vivek

cardosocea · Jan 9, 2019

What have you tried to do to troubleshoot the hissing sound?

How did you connect them together for redundancy? With a diode unit?
Did you try running them separately to see if the hissing sound comes from one of two of them?
Did you have an oscilloscope at hand to see whether the output has some funky frequency?
Are you sure it is the power supplies and not something powered by them?

Vivek_PV · Jan 9, 2019

Power distribution diagram

We are using two diode units. I am attaching the power distribution diagram which will give you a clear picture. As of now i had not done any experiments. Client inspection is going in for this project now. They asked about the hissing sound suddenly.

bright676 · Jan 9, 2019

"As of now i had not done any experiments."

Experiments? Perhaps you should get more experienced help before experimenting.

cardosocea · Jan 9, 2019

Interesting redundancy setup... any chance that the two outputs from the diode units are connected up front and there's a voltage difference between them?

Testing the stuff I asked about should give you an indication, or further information of what may be wrong.

OkiePC · Jan 9, 2019

That hissing sound is the smoke trying to escape. You must not let that happen.

sbaum · Jan 9, 2019

I've noticed some power supplies (Sola, Phoenix Trio, etc) will emit a sound when powered with no load. I reckon it could be described as a 'hissing' sound.
If that's what they're hearing then I wouldn't be too concerned.

tragically1969 · Jan 9, 2019

Vivek_PV said:
Hello All,

We are using two "QUINT-PS/1AC/24DC/20 - 2866776" Power supplies for one of our project. The input power is single phase 240V and out power is 24VDC which is used to drive PLC CPUs, I/O Racks, and solenoid valve relays.
There is some kind of hissing sound coming from the Power supplies when turned ON. The total estimated load is 16.39 Amps and 430 watts.
The two power supplies are for redundancy.
Is there any specific reason behind this behaviour?
Please help

Regards
Vivek

Which redundancy modules are you using, whats the part number ?

As above, are you sure you haven't got the output of the PSU's connected at the front end of the diode modules, that would cause issues for sure.

Switch Mode PSU's do make a very high frequency buzz sometimes which could be describes as a hiss, i would speak to Phoenix as a starting point.

bright676 · Jan 9, 2019

Maybe he has some spare smoke saved from one of his other experiments.

Saffa · Jan 9, 2019

I have come across some switchmode supplies which hiss, like Sbaum mentioned. This is generally when there's no load and the pulse width is low. Its just a harmless side effect of a switching frequency within the audible range.

Now this may be something very different. You mention 16A of total load on a 20A PSU. That's not a lot of margin and I'd consider that a heavily loaded system. Is everything powered up yet or are you still doing pre commissioning? I'd measure the load current for each PSU output and report back actual numbers.

I do also see these are connected to individual UPS supplies. Are they double conversion online type units? Depending on the quality of the UPS the actual output could be full of harmonics and switching noise. Either check with a scope or try plugging your DC power supplies directly into mains power.

GaryS · Jan 9, 2019

An observation
I down loaded the manual for tat power supply
These are adjustable power supplies 18VDC to 29.5 VDC
The asy on the last page they can be hooked up as parallel supply or as a redundant Supplies
But I have never seen 2 adjustable power supplies in parallel. All the parallel supplied I have worked with have a jumpers that must be changed and a control wire run on to the other to allow 1 power supply to act as a master and control the voltage level of both. If you hook up 2 power supplies the output voltage must be exactly the same or you will pass current from the supply with the higher voltage to the one with the lower voltage. But the problem gets worse because both supplies will do everything they can to regulate the output of both to the voltage level set in their control. The higher supply will supply more current and the lower will try to dump the excess power. As we all know they will eventually destroy them selves.
Most modern power supplied are a switched type and you must be very careful when working with them.
I also noticed that both power supplies are 20 amp output with 40 amps combined. But the drawing you posted show that both power supplies are 40 amp with a combination of 80 amps. There seems to be a big difference in what called for on the drawings and what you supplied.

Vivek_PV · Jan 10, 2019

cardosocea said:
What have you tried to do to troubleshoot the hissing sound?

How did you connect them together for redundancy? With a diode unit?
Did you try running them separately to see if the hissing sound comes from one of two of them?
Did you have an oscilloscope at hand to see whether the output has some funky frequency?
Are you sure it is the power supplies and not something powered by them?

I ran the power supplies separately. Very less sound was coming from the power supplies which i think is normal. But when ran together, very high sound is coming out. I measured the output current in no load condition, which is 20 mA for one power supply and 19 mA for the other one.

Saffa · Jan 10, 2019

GaryS said:
An observation
I down loaded the manual for tat power supply
These are adjustable power supplies 18VDC to 29.5 VDC
The asy on the last page they can be hooked up as parallel supply or as a redundant Supplies
But I have never seen 2 adjustable power supplies in parallel. All the parallel supplied I have worked with have a jumpers that must be changed and a control wire run on to the other to allow 1 power supply to act as a master and control the voltage level of both. If you hook up 2 power supplies the output voltage must be exactly the same or you will pass current from the supply with the higher voltage to the one with the lower voltage. But the problem gets worse because both supplies will do everything they can to regulate the output of both to the voltage level set in their control. The higher supply will supply more current and the lower will try to dump the excess power. As we all know they will eventually destroy them selves.
Most modern power supplied are a switched type and you must be very careful when working with them.
I also noticed that both power supplies are 20 amp output with 40 amps combined. But the drawing you posted show that both power supplies are 40 amp with a combination of 80 amps. There seems to be a big difference in what called for on the drawings and what you supplied.

Gary, the Diode unit takes care of the fact that one supply might have slightly higher output voltage. That unit will provide the lions share of the current. But that's ok, this is a redundancy application not a load sharing application.

The diodes prevent any reverse current flow from one power supply to another.

Vivek_PV · Jan 10, 2019

Saffa said:
I have come across some switchmode supplies which hiss, like Sbaum mentioned. This is generally when there's no load and the pulse width is low. Its just a harmless side effect of a switching frequency within the audible range.

Now this may be something very different. You mention 16A of total load on a 20A PSU. That's not a lot of margin and I'd consider that a heavily loaded system. Is everything powered up yet or are you still doing pre commissioning? I'd measure the load current for each PSU output and report back actual numbers.

I do also see these are connected to individual UPS supplies. Are they double conversion online type units? Depending on the quality of the UPS the actual output could be full of harmonics and switching noise. Either check with a scope or try plugging your DC power supplies directly into mains power.

We are doing pre commissioning. We have a simulation panel for all inputs and outputs. I measured the output currents when no load. For one power supply, it is 20mA and for other it is 19mA.
UPS supplies are not connected. They are directly connected to the mains

tragically1969 · Jan 10, 2019

Saffa said:
Gary, the Diode unit takes care of the fact that one supply might have slightly higher output voltage. That unit will provide the lions share of the current. But that's ok, this is a redundancy application not a load sharing application.

The diodes prevent any reverse current flow from one power supply to another.

I think it would still be worth him clarifying which Diode Modules he is using.

Phoenix Power supply unit hissing sound

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