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I spend most of time on a boat (not on holiday :/ ) where a huge generator provides electricity. The potential problem is that the output is very dependent of the "mood" of the engine. Sometimes the frequency of the AC that goes to the sockets of the cabins is 48 Hz, sometimes 52 Hz. Anyway, generally between 48-52. (EU norm 50 Hz)

My question is regarding the safety of my equipment such as notebook/laptop. My theory is that this fluctuation of frequency only harms the PSU/Charger that converts AC to DC for my laptop, therefore that will die first, before everything else. What do you guys think? Can the internal components be harmed as well, or is my theory correct? Can this harm other appliances?

Also, I am curious what kind of UPS can regulate such fluctuations into 'flat' 50 Hz (EU) and stable voltage and current?

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    \$\begingroup\$ How many watts is the supply rated for? \$\endgroup\$ – Spehro Pefhany Sep 6 '19 at 8:57
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    \$\begingroup\$ Input: 100-240V~2,5A 50-60Hz Output: 19.5V 6.7A 130W \$\endgroup\$ – Adam Toth Sep 6 '19 at 9:16
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    \$\begingroup\$ XY problem! Has anything failed at all? \$\endgroup\$ – winny Sep 6 '19 at 11:44
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    \$\begingroup\$ @winny The XY problem is the engine having a mood. It should be 50Hz +-0.5 with only short dips and swells when significant kilowatts are switched. Unstable speeds often means very poor voltage regulation, and this really does damage equipment. \$\endgroup\$ – Jeroen3 Sep 6 '19 at 18:52
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    \$\begingroup\$ @Jeroen3 I see no evidence of that. My guess is that OP has a solution he is trying to find a problem for. \$\endgroup\$ – winny Sep 6 '19 at 19:47
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Don't worry. Your PSU doesn't really work with AC.

Most modern PSU fist change the AC to DC via a rectifier. The internal electronic then creates an own AC used to transform the voltage to the desired one. The internal AC has a much higher frequence to be more effecient.

Most PSUs work with frequencies from 0 to over 60Hz. Even DC with down to 80V is possible. So anything up to 60 Hz should be fine, if you have between 100V and 240V.

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    \$\begingroup\$ Locomotive engineers have been known to charge their laptops on the 75VDC battery voltage. The default 75VDC outlet on a locomotive is a NEMA 1-15, which laptop supplies plug straight into. \$\endgroup\$ – Harper - Reinstate Monica Sep 6 '19 at 18:17
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    \$\begingroup\$ This is not necessarily true in extreme cases. If the AC frequency drops a lot, the rectified AC starts to look like pulsed DC, which effectively would cause the supply to turn off and on a lot of times, if there isn't enough capacitance to handle this condition. This is not a problem for clean DC, or a higher AC frequency. \$\endgroup\$ – nitro2k01 Sep 6 '19 at 18:50
  • \$\begingroup\$ Also, PFC circuits in power supplies could suffer from such handling. Undervoltage could also severely stress the PSU. However, all such are unlikely to damage more than the outboard PSU that should be easily replaceable anyway. \$\endgroup\$ – rackandboneman Sep 6 '19 at 20:22
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My theory is that this fluctuation of frequency only harms the PSU/Charger that converts AC to DC for my laptop, therefor that will die first, before everything else.

As stated in @rundekugel 's answer, the frequency of the AC line does not matter unless it's much higher than 60 Hz (e.g. 1kHz) since the actual converter inside the PSU requires DC input. There's a bridge rectifier and reservoir capacitor(s) inside the PSU for this purpose and the bridge rectifier works well with even 100Hz.

Can the inside components be harmed as well or is my theory correct? Can this harm other appliances?

Instead of frequency fluctuations, spikes on the AC line can be harmful but I'm not sure if it's likely to see those spikes on the AC line due to the motor / alternator. A well-designed equipment "should" have protection devices (i.e. filters, suppressors, etc) for unwanted components (e.g. spikes, high frequency radiations via conduction, etc.) on the AC line. Laptop adapters/chargers do have these protections.

Some AC motors' speed depend on the frequency of the supply voltage. Thus, if you have any equipments contain those kind of AC motors then these equipments may be affected by the frequency fluctuations.

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Supplies in the 130W range sold in Europe (I believe more than 75W) are required to have power factor correction so the input section is rather more complex than some other answers assume. From this source is a block diagram:

enter image description here

I still think it's more likely that it is voltage surges causing your problems, assuming you are experiencing failures. Active PFC circuits (any modern supply with PFC will be active rather than passive) expose some input elements to surges more than simple rectifier input circuits.

There are power conditioners sold for use in developing countries that might help protect your supply.

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As you just said in comments, the laptop has a wide acceptable input range. That is not surprising since it is a switching power supply.

Others have discussed how laptop supplies (like a great many loads) simply do not care about frequency inside conceivable ranges. They state 50-60Hz because 50Hz or 60Hz is the frequency of essentially all terrestrial power.

As far as voltage, they are clearly stating a working range of 100-240V, and again they're just regurgitating the range of essentially all terrestrial power: 100V in Japan or 240V in the UK. The practical limits will be:

  • too high a voltage causing insulation or component breakdown, but insulation is cheap.
  • too low spikes are just a momentary low voltage, and the switcher will try to ride through it. The only risk is that it shouldn't spend minutes at too-low voltage, because lower voltage means the switcher will draw more current, and at a a point, that will overheat and burn up current pathways in the device.

I would advise getting a physical, copper-and-iron, wound stepdown transformer from 240V to 120V. That will passively dampen spikes, and smooth out some power issues. It will also divide the voltage by 2, meaning the power would have to jump to 480V before it would exceed the voltage spec.

A transformer built for 50Hz is slightly better. The size of the iron core decideds a transformer's ideal frequency, and 16% won't matter on a transformer this small. (I'm assuming 100-500 W).

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Other equipment

Within sane range (say, maximum aircraft 400Hz)... Obviously, anything that rectifies doesn't care about frequency. Also, resistive heaters don't care about frequency. Things using a variable frequency drive don't care about input frequency, because they are slicing and dicing to make their own frequency.

Rotary machines (including transformers) do care, however. As alluded, transformers are tuned for a frequency by the size of their iron core; motors as well. A motor or transformer will be very, very unhappy on railroad 16.7 Hz or aircraft 400Hz.

Clocks depend on 50/60Hz being right on the button. There was a newspaper-worthy scandal in the EU as the grid operators were not able to sustain 50.000 Hz, and had to "speed up the grid" in the evening to catch everyone's clock up by the few seconds they had drifted. The grid is managed that precisely.

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  • \$\begingroup\$ Also, very cheap LED lights might turn brighter on higher frequency (those without a proper driver, but relying on a capacitor in series to limit current). But yes, proper switching power supplies (like laptop chargers) don't care about frequency. \$\endgroup\$ – Nyos Sep 6 '19 at 19:19
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One aspect that has not been clearly mentioned is that in a huge ship (I suppose it is huge, since you said the electrical power is produced by a huge generator) you have many powerful electrical motors connected to the electrical line.

So the electrical system of a ship (especially if it is a tanker or a freighter, as opposed to a cruise ship) behaves more like an electrical system in an industrial environment, than a household electrical system.

Normal laptop power supplies do have overvoltage protection devices, but they are designed to withstand AC line spikes that usually happen in a household/office situation.

In an industrial environment, where many inductive loads are electrically near the power supply, spikes with higher energy content may be generated (bigger amplitude, longer duration). These could stress the power supply protections so much that they could fail in the end, so leading to a potential damage to the power supply main circuitry itself.

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