How bad is the quality of my mains voltage and what can I do to improve it? - Page 4

DF96 · 1st February 2012, 05:56 PM

Do Chinese factories worry about EU PFC regulations?

AndrewT · 1st February 2012, 05:59 PM

Do Chinese workers bother with any regulations?

S.A.G. · 1st February 2012, 06:09 PM

don't get me started on this...

Rodeodave · 2nd February 2012, 06:54 AM

Scope is not clipping, the waveform looks the same on the secondary of a 15VAC transformer. Plus the probe is attenuating 10-fold.

EN50160 allows for 8% THD, see here for example: http://www.evu-messtechnik.de/docs/E...EN_50160-i.pdf. The individual harmonics must not exceed 5% for 3rd, 6% for 5th, 5% 7th and so on.

Meanwhile the engineering guy replied, and he offered to get a measurement done at the house connection, with the power company covering the costs. This shall be interesting.

dtproff · 2nd February 2012, 12:58 PM

OK... that takes care of my stupid ideas. Let us know how this turns out.

Tony

S.A.G. · 2nd February 2012, 03:44 PM

Rodeodave,

I've checked the standards and it turns out that you are right on the EN 50160 8% THD, the 3% number is from MIL-STD-1399 Type III (400Hz). OOOOOPS, sorry for the confusion.

Good to hear that the power company is taking care of your issue.

Regards

mrmodemhead · 2nd February 2012, 05:10 PM

Here's what the mains look like in a residential area outside Raleigh, NC, USA. The larger trace is from Line to Ground, at 50V/div. The smaller trace is from Neutral to Ground, at 1V/div. This second trace is showing the voltage drop on the neutral line from where it is bonded at the distribution panel, to this outlet, which effectively represents the current on this branch circuit.

The loads are a 1000VA UPS serving one PC and the usual peripherals, a small studio amp playing music at low level, a 20W fluorescent light fixture with electronic ballast, and the scope itself.

I doubt that flattened peaks are all that unusual, for the reasons already explained.

zigzagflux · 2nd February 2012, 05:11 PM

I don't know that there is much they will (can) do for you. As has been explained (and partially ignored), this flat topping is typical, and not at all abnormal in today's electronic world without power factor correction (electronic control system that forces current draw as a sine wave).

At best, they could install a larger transformer to reduce the source impedance. Voltage drop across impedance at the peak current is the root cause. This is a result of ohm's law. You don't filter it out; there is no defective equipment. It is expected.

A larger transformer will still exhibit some flat-topping, just less extreme.

1st February 2012, 05:59 PM	#32
AndrewT diyAudio Member Join Date: Jul 2004 Location: Scottish Borders	Do Chinese workers bother with any regulations? __________________ regards Andrew T.

2nd February 2012, 06:54 AM	#34
Rodeodave diyAudio Member Join Date: Dec 2004 Location: in the alps Blog Entries: 1	Scope is not clipping, the waveform looks the same on the secondary of a 15VAC transformer. Plus the probe is attenuating 10-fold. EN50160 allows for 8% THD, see here for example: http://www.evu-messtechnik.de/docs/E...EN_50160-i.pdf. The individual harmonics must not exceed 5% for 3rd, 6% for 5th, 5% 7th and so on. Meanwhile the engineering guy replied, and he offered to get a measurement done at the house connection, with the power company covering the costs. This shall be interesting. __________________ Gravity - Making the G since 13.7 billion B.C.

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1st February 2012, 05:56 PM	#31
DF96 diyAudio Member Join Date: May 2007	Do Chinese factories worry about EU PFC regulations?

1st February 2012, 06:09 PM	#33
S.A.G. diyAudio Member Join Date: Jun 2004 Location: Milano	don't get me started on this...

2nd February 2012, 12:58 PM	#35
dtproff diyAudio Member Join Date: Oct 2008 Location: Plano, TX, USA	OK... that takes care of my stupid ideas. Let us know how this turns out. Tony

2nd February 2012, 03:44 PM	#36
S.A.G. diyAudio Member Join Date: Jun 2004 Location: Milano	Rodeodave, I've checked the standards and it turns out that you are right on the EN 50160 8% THD, the 3% number is from MIL-STD-1399 Type III (400Hz). OOOOOPS, sorry for the confusion. Good to hear that the power company is taking care of your issue. Regards

2nd February 2012, 05:11 PM	#38
zigzagflux diyAudio Member Join Date: Oct 2006	I don't know that there is much they will (can) do for you. As has been explained (and partially ignored), this flat topping is typical, and not at all abnormal in today's electronic world without power factor correction (electronic control system that forces current draw as a sine wave). At best, they could install a larger transformer to reduce the source impedance. Voltage drop across impedance at the peak current is the root cause. This is a result of ohm's law. You don't filter it out; there is no defective equipment. It is expected. A larger transformer will still exhibit some flat-topping, just less extreme.

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