Mysterious failure of a Siemens mini circuit breaker C6A (5SY41)

From one day to another this mini circuit breaker stopped working, I had been using it wrongly as a on/off switch and was wondering if there was a mechanism inside to disable it after too many on/off switches, as MCBs are only rated for a finite number of operations.

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Teardown video of Eaton PowerWare 30 kVA UPS

Here is a video from taking apart 3 UPS units from Eaton PowerWare, these are 30 kVA units that was previously described in pictures and text in one of my earlier teardown articles: http://kaizerpowerelectronics.dk/electronics/teardown-eaton-powerware-30-kva-ups/ 

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Teleste AC2000, teardown of a 862 MHz cable TV amplifier

This Teleste AC2000 is a cable TV amplifier that is configurable through different insert jumpers for setting up attenuation/equalization, diplex filters, return amplifier or a transponder making it remote controllable.  This is a dual 39 dB amplifier in the range from 5 to 862 MHz which enables it of delivering 110 channels. 

This particular amplifier is set up for one input, a bypass for next amplifier in the chain and two outputs. There is no transponder installed.

These small amplifiers are used in houses where it is not practical to use a receiving antenna to get the signal from the broadcast headend transmitter. They are called a “service drop”

Instead CATV is used, short for community antenna TV, a large receiving antenna is used, a cable connection runs out to every house in the neighborhood and each house has one of these amplifiers. The return path amplifier can also send some of the signal back into the line to keep the signal good enough for the next house.

It is installed in a weather proof enclosure meant for outdoor wall installation where it is most practical to have the antenna input cable come up from the ground and from there on route cables into houses and apartments.

The internal power supply has a input voltage range from 27 to 65 VAC/35 to 90 VDC and has two output voltages. 24 VDC at 1400 mA maximum and 12 VDC at 900 mA maximum. 

The manufacturer specifications of this cable TV amplifier

  • 2-3 outputs by internal splitting
  • Spectrum analyser function
  • Plug-in module adjustments
  • Fixed station memory for electrical identification
  • Electrical gain & slope control modules
  • Optional high performance return amplifier
  • Downstream signal path 85…862 MHz (110 channels)
  • Input attenuator control range 20 dB
  • Input equaliser control range 25 dB
  • Mid-stage slope 8 dB
  • Flatness ± 0.4 dB
  • Upstream signal path 5…65 MHz

If transponder was installed:

  • US ingress monitoring
  • Return path ingress switches ON/ -6 dB / OFF control
  • 65 VAC voltage measurement
  • Local DC voltages, 12 V and 24 V
  • Temperature measurement
  • Gain and slope controlling in ALSC mode
  • Individual channel level measurement (AC6951)
  • Spectrum analyzer function
  • Lid status monitoring
  • Local connection indication at server
  • Configuration data stored in main board eeprom (station memory)

Attenuators, for all TVs manufactured after 1995, the signal strength at the TV should be between -10 dB and +15 dB, this is achieved with 20 dB range on inserts in this amplifier.

Equalizer or also called slope, is the difference in signal strength between the highest and lowest channels. This is also handled with inserts in a 25 dB range for input and 8 dB for mid-stage. To get a frequency response of ± 0.4 dB, also called flatness.

Attenuators and equalizer inserts are for the most a plastic container with the following content, a gold plated 3-legged 2-3 resistor setup.

A diplexer is a passive device that implements frequency-domain multiplexing. Two ports (e.g., L and H) are multiplexed onto a third port (e.g., S). The signals on ports L and H occupy disjoint frequency bands. Consequently, the signals on L and H can coexist on port S without interfering with each other.

The heart of this box is the CATV amplifier modules which was the popular choice of silicon in amplifiers of this type from the 1990’s.

Features of these hybrid amplifier modules for CATV systems operating over a frequency range of 40 to 450 MHz at a voltage supply of +24 V and intended for use as a line-extender.

  • Excellent linearity
  • Extremely low noise
  • Silicon nitride passivation
  • Rugged construction
  • TiPtAu metallized crystals

 The internal construction of the hybrid amplifier module can be seen below.

Close-up of the six transistors in the module.

Video with explanation of the different parts while the amplifier is being taken apart.

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Kone elevator control/power electronics panel teardown

This is a Kone Elevator control and power electronics panel dated around 1999-2000 according to stickers and test marks. It does not appear to have had a user interface, unless that was connected to the RS232 port.

The front reveals a control board with a -12 VDC, GND and +12 VDC power supply at the top, used primarily for the gate drive of the IGBT module and rest of the logic runs on +5 VDC.

The controllers heart is the Intel N80C196KC20 microcontroller, known as the “80196” family of microcontrollers, it was discontinued by Intel in 2007 without any newer replacement parts available. It is a 16-bit 20 MHz microcontroller which have two ST M27C1000 8x 256 KB EEPROMs connected. One with the main program and the other is marked in the PCB to have a test program. To store data while the controller is powered off there is a ST M48Z35Y ZEROPOWERRAM which is 256 KB of SRAM, besides the SRAM module there is a voltage sense and switching circuitry along with a lithium battery in the package.

There is a large pin-header for connecting a flat cable with all peripheral circuits like buttons, level indicators, sensors and safety monitoring devices. There is a funny, yet a little freightening, push button switch on the board that says “Full power”, along with other texts that refer to “Offset test”, “Record out” or “Test program”

To control the phase angles of the motor there are three TLC 8-bit DACs which get their digital signal from the microcontroller and delivers a variable phase angle signal to the IGBT driver board.

The heart of the power electronics is a 3 phase Eupec BSM50GD120 IGBT module which is rated for 50 Ampere at 1200 VDC. The DC bus filtering is two RIFA 1000 uF / 350 VDC electrolytic capacitors. The output from the drive goes through 3 ring core inductors before going to the motor connection terminals.

Mains input goes through a 3 phase filter before it goes to IXYS 3 phase rectifier and brake chopper module protected with MOVs. There is a separate brake module that dumps energy from the motor to two power resistors.

There is two heavy shielded cables going off the PCB with a DC+ and brake engage wires to the large mechanical brake on the lift itself to lock it into place when not moving.

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SSTC and DRSSTC musical modulator

Since Martin from ctc-labs.de decided to close down his website, which was all written in German, I asked him for permission to translate and publish some of his content to keep it online and public for others to use.

So here is the translated article about his small and simple analog circuit that can be use to make a Tesla coil play music. Using just a op-amp and a 555 timer it is possible to recreate the effect from expensive MIDI modulators by instead just using a analog signal. This method is ofcause not as precise as with digitally microcontroller based MIDI interrupters.

Read the full article with illustrations and schematics and learn how to play music with your Tesla coil.

musical_interrupter_billede2

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Kaizer DRSSTC update #7 – Show and tell

While we had the box open for removing the real-time current control, as you can see in the previous post, I did a walk through of how the coil is put together and what parts have been used.

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CM600DU-24FA IGBT – Removal of RTC over-current protection

The real-time current control (RTC) that can found in some IGBT modules is a protection against short circuits in f.ex. motor drives where they could have been used.

The conditions on which the RTC acts is however sharing area with using IGBT bricks in Tesla coils, as the RTC will never interact while operating the IGBT within its Safe Operating Area (SOA) there is still a risk that it will be activated when driving a IGBT hard in a DRSSTC where it could be used to switch currents many times its rating.

Below is a quote from a Powerex paper on how the RTC works and behaves. I added a few outlines and extrapolated the graph to show the typical 24 VDC gate drive in a DRSSTC.

[1] 4.0 RTC Description and Behavior

F-Series IGBTs include an integrated real-time current control (RTC) circuit for protection against short circuits, which was originally developed for intelligent power modules (IPMs). The RTC is a separate chip wire-bonded directly to the IGBT die and mounted adjacent to it. During normal operation of the device, the RTC is effectively “transparent” to the gate driver. Its power supply is drawn from the main collector-emitter path of the IGBT, so it imposes no additional drain on the gate driver. The RTC is connected to a current mirror emitter on the trench IGBT chip. A simplified diagram of this is shown in Figure 3.

When the IGBT operates in a short circuit, the RTC detects the excessive current in the IGBT and reduces the gate-emitter voltage to limit the short-circuit current. The gate-emitter voltage is reduced to less than 12V, compared with the normal recommended value of 15V. The effect of gate-emitter voltage on short-circuit current is shown by Figure 4. It is important to note that the RTC acts only to limit short-circuit current; it does not switch off the IGBT. Therefore the gate driver circuit should be designed to ensure that the IGBT is turned off within 10µs of a short circuit occurring. The RTC limits the short circuit collector current to 2-4 times rated current, depending on the junction temperature of the IGBT and the short circuit di/dt.

The minimum trip threshold for the RTC is 2 times the rated current of the device and occurs at high Tj and high di/dt. Therefore operation of the IGBT within its normal switching SOA is unaffected by the presence of the RTC

In the following video I show and explain where to locate the RTC circuit and how to disable it with a simple tool like tweezers. Side cutters can also be used but it will make a bigger mess and ruin more of the protective goop that surrounds the die and bonding wires.

References

[1] Powerex, “Featured Products Technology”

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Kaizer DRSSTC III update #6 – First full power test after removing RTC

After cutting out the bonding wires to the RTC circuit of the CM600DU-24FA IGBT bricks, which we thought could be one of the reasons that we were not able to trip the 1500 A OCD setting, we had a short test run to witness performance. I will do a video with more details of the real-time current control removal later.

While it might have limited the operation a little bit, it was nowhere near hindering performance, this coil is just so high impedance that it runs long on-times instead of high peak currents.

Fed with 3×400 VAC through a variac resulted in a 0.6 power factor. After roughly 8-10 test runs at up to 2 minutes, with peak power consumption hitting 14 kW at 500 BPS, 200uS, the total power consumption over all the tests was 0.281 kW/h, 0.331 kVAr/h and 0.438 kVA/h.

First video shows the coil running 120-500 BPS at somewhere around 200 uS on-time. Peak power consumption from the 3×400 VAC supply was around 14 kW. Sparks are 3 meters to ground and somewhat shorter to the ladder.

Second and third video show tests with a static load, peaking at about 10-14 kW depending on MIDI or interrupter is used.

and

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Astro HVO-Vario G 38, teardown of a 862 MHz cable TV amplifier

These are highly modular cable TV amplifiers, they are set up by using a wide range of different insert cards with different frequency ranges or options. These are 38 dB amplifiers in the range from 47 to 862 MHz.

This particular amplifier is set up for 862 MHz, 42 channels and has a return path amplifier for keeping signal strength on the line good. The line equalizer is used to adjust for how close to the community amplifier the house is located, the further away, the less attenuation is needed.

These small amplifiers are used in houses where it is not practical to use a receiving antenna to get the signal from the broadcast headend transmitter. They are called a “service drop”

Instead CATV is used, short for community antenna TV, a large receiving antenna is used, a cable connection runs out to every house in the neighborhood and each house has one of these amplifiers. The return path amplifier can also send some of the signal back into the line to keep the signal good enough for the next house.

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Finished project: Merlin Gerin PM700 power meter

Two days ago I conducted the first successful resistive load test of a 3 phase power meter that can measure voltage, current, power consumption, harmonic distortion and power factor.

Read all about the construction and see all the pictures and video demonstration here.

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