Category: Electrical

LED plate driver failure #3 & 4 – 24W round plate

This article documents a third and fourth failure of a 24W LED oyster. The luminaire was purchased complete on eBay for about $45.

About 12 months after the last driver replacement, the driver has again failed. Again it is the mains filter capacitor that has failed.

The driver was replaced with the same type, we will see how long it lasts.

Within a few days of replacing the driver, the lamp failed again. This time it was the LED plate.

The LED plate is a 48S2P configuration of 0.5W 5730 LEDs. The fail either as short circuit or open circuit. If one fails short circuit the plate keeps working just two LEDs are dark. If one fails open circuit, its pair will overheat and go open circuit then the whole plate is dark. Continue reading LED plate driver failure #3 & 4 – 24W round plate

Last update: 17th November, 2024, 9:07 AM

Mains (230VAC) DC power supplies for ham radio equipment – AU

One sees a lot of discussion on social media of 12VDC power supplies for ham radio equipment. Some of the recommendations are unsafe.  Bear in mind that the user could well be a young person with little knowledge and experience and unsafe equipment may put not just themselves at risk of electrocution, but other members of the family / household, people who might try to rescue them.

Firstly, before someone rushes to correct me on the matter of 230V: Continue reading Mains (230VAC) DC power supplies for ham radio equipment – AU

Last update: 9th August, 2024, 7:10 AM

Review of after market DeWalt compatible 18V 7Ah lithium-ion tool battery

I purchased on of these batteries on Big-W online for a mid-high price ($77), expensive enough compared to genuine to expect it would have near to rated capacity.

Above is a pic of the battery advertised. The delivered battery was labelled 7Ah. Continue reading Review of after market DeWalt compatible 18V 7Ah lithium-ion tool battery

Last update: 17th June, 2024, 7:00 AM

Clipsal C2025 WE issues

I set about the relatively simple task of replacing a faulty PDL GPO (general purpose outlet – a power point) with a Clipsal double GPO.

The experience might give readers cause for concern if they have Australian made Clipsal C2025 WE GPOs (pictured above) in their residence, workshop or workplace. The label “5” is an addition, the GPO does not have a part number or manufacturing batch / date on it anywhere. Continue reading Clipsal C2025 WE issues

Last update: 30th March, 2024, 9:40 AM

Evaluation of Aliexpress sourced EBM315 battery packs (for DB3DL2)

In Repack of Hikoki / Hitachi EBM315 battery pack (DB3DL2) I discussed the repack of a battery pack. At the same time I also ordered a no-name replacement 1.5Ah battery on Aliexpress for $25 incl shipping… with some reservation as most batteries I have purchased on Aliexpress have failed to deliver half of the rated capacity.

So, the battery arrived and I tested it, the purple trace above, and I was pleased to see that it exceeded the rated capacity a little.

So, I purchased another from the same seller, and it duly arrived, and to my surprise, it exceeded rated capacity by 30%.

Both batteries recharge properly on the Hitachi / Hikoki charger.

Time will tell whether they are good value. In any event, they use screws to hold the cap on so they can probably be repacked with good cells.

Last update: 16th March, 2024, 10:25 AM

Repack of Hikoki / Hitachi EBM315 battery pack (DB3DL2)

I have had a Hitachi DB3DL2 ‘pencil’ type cordless screwdriver for about 12 years, and one of the supplied two batteries (EBM315 1.5Ah) has just failed. This is not the first failure, the charger failed after about five years use and the LED push button became electrically leaky flattening the battery so the push button was removed. The second battery is still working, but at about 65% capacity.

It is actually a really good tool to use, and so worth trying to extend its life. To that end:

  • I purchased a new genuine Hikoki (new name for Hitachi -Koki) charger on Aliexpress for about $80 shipped (they are more like $150 locally);
  • I purchased an after market EBM315 1.5Ah battery on Aliexpress for about $25 shipped;
  • I purchased locally two Panasonic NCR1650B unprotected 3.4AH 18650 cells to repack the two original batteries; and
  • repacked the failed battery.

Above is a capacity test of the new Aliexpress 1.5Ah battery and the working 14 year old Hitachi battery. The little squiggles are concerning, to be further investigated. It is my experience that most rechargeable batteries purchased on eBay and Aliexpress grossly fail to meet specified capacity, the one is a welcome change… though note the quite low cell voltage to achieve rated capacity. Continue reading Repack of Hikoki / Hitachi EBM315 battery pack (DB3DL2)

Last update: 19th June, 2024, 10:06 AM

Paralleling two synchronous AC generators – phasor diagram with AVRs

This article Paralleling two synchronous AC generators presented phasor diagrams for two synchronous generators in parallel, and Paralleling two synchronous AC generators – simple AVR discussion discussed a simple automatic voltage regulator system that can be used to share two identical machines.

To recap, the first configuration presented follows.

Above is a phasor diagram of two machines of the type discussed in parallel. This is just after ACB closure, and they are not well adjusted in this case to allow visibility of the various phasors. Continue reading Paralleling two synchronous AC generators – phasor diagram with AVRs

Last update: 25th February, 2024, 9:34 AM

Paralleling two synchronous AC generators – simple AVR discussion

Paralleling two synchronous AC generators explained synchronisation and parallel operation of two generators, discussing sharing of real and reactive power.

In that discussion, the engines were speed governed, but voltage was manually controlled by adjusting excitation current. The phasor diagram showed that there is a relatively large source impedance (dominated by the synchronous reactance), EMF is around 1.5 times Vt, and terminal voltage Vt will vary widely with changes in load as a consequence. Continue reading Paralleling two synchronous AC generators – simple AVR discussion

Last update: 17th February, 2024, 10:15 PM

Paralleling two synchronous AC generators

This article discusses adding a second synchronous AC generator in parallel with a running synchronous AC generator.

For explanation, a simple context is used, two identical diesel engine driven generators with governed speed, no droop compensation, otherwise largely manual control, simple equivalent circuit of the machines. The complexity of other factors like  harmonic currents etc are not discussed.

The simple model is useful as it underlies practical machines and is a good configuration to introduce the main principles of the operation.

To avoid typos, some of the text uses Python formatting of complex numbers.

Prerequisites for paralleling three phase synchronous generators

Prerequisites for paralleling three phase machines are:

  1. same phase sequence (eg both A-B-C);
  2. nearly the same voltage; and
  3. nearly the same frequency, and eventually same phase.

(1) does not apply to a single phase machine. (1) is resolved at the time of wiring up the machines and circuit breakers used to connect them to the bus. Unless changes have been made to machines or wiring, sequence should not need to be checked. After any reconfiguration or wiring changes phase sequence should be checked by a competent person.

Phase sequence is checked using an instrument like one of these above. The left one is a small three phase motor, the right one is electronic and shows sequence with an LED. Continue reading Paralleling two synchronous AC generators

Last update: 24th February, 2024, 10:47 AM