you run the risk of frying the igbt - try a relay ...
p.s. you only need one triac - the other is redundant -
Not sure I see a benifit of the resistors over the NTC. Was planning on using a something like a SL22 5R012 that costs under $2. The triacs are there so that an enable signal can turn on the power supply through the linear regulator. A "switch" would wind up being another relay. I prefer solid state components over magnetics. Controlling the IGBT or relay or whatever it winds up being that bypasses the current limiting device is the main question. I need a voltage or current reference from the board to switch this bypass, I do not want to control it externally. So the switch has to operate from a voltage reference on the DC bus side when it gets above 250v or so as you say or when the inrush current levels off, but how do I get this reference? I can find no suitable shunts and haven't figured it out otherwise yet.also the thermistor could be 2 x 10W 68E resistors in series, with no triacs on the mains - just a switch - then close the relay after Vcap = 250VDC say - or just after 2 seconds ....
Suppose you pre-charge the capacitors directly from an auxiliary power supply? Install a plain diode and resistor, calculated so caps take a second or two to reach 90 percent running voltage. Power ratings can be small due to short operating time .
Turn it on first briefly, then apply full power. The diode prevents accidental backward current flow. Put several diodes in series to create a threshold voltage so it won't conduct during brief voltage drops in your circuit.
Hi,
I don't think that a 2200W power supply with just rectifying the input to a capacitor bank is according nowadays rules.
I'd use a PF stage with soft start to smoothly charge the capacitors.
Klaus
To illustrate here's a simple simulation of 2000uF charging through resistor and diode from 240 VAC source (peaks=340V). Timeframe 1 second.
View attachment 157417
Looking at your schematic it could be done by adding a switched resistor in parallel with each of your triacs. These can take the place of your NTC thermistor since all do a similar job for a while after power-up. It's a question which works better, a thermistor in the path all the time, or resistors in the path briefly.
What watt rating should the resistor be? The net dissipation is about 120W for one second. However it's hard to be sure of the amount of stress resulting from high power applied for a second or two, then idle for a long time. You may find 5 or 10W is sufficient.
It was never the intention to "leave the thermister in the path the whole time", bypassing it after inrush was always the intention.
Another possibility is a choke filter. This is useful for smoothing current spikes which are typical with capacitor filters. A choke might go on the AC side or it might go after the diode bridge (or both places). Perhaps in the area of 10-100 mH. If you choose too great a Henry value, it causes voltage drop to your load. It needs to handle the Ampere amount in your system. 2200W at 240VAC calculates to 9A.
There are also the sensible suggestions in posts #2 & 4. I didn't mean to distract from them.
- - - Updated - - -
Also consider that power factor error comes into play when capacitors and inductors are involved.
Something like this after the rectifier?
9A RMS .... is the optimum value and only true for non phase shifted pure sinusoidal signals.2200W at 240VAC calculates to 9A.
Hi,
9A RMS .... is the optimum value and only true for non phase shifted pure sinusoidal signals.
For a rectifier - capacitor solution the RMS current (which is responsible for heating of the wires) is much higher.
An additional L will reduce the RMS current, but it still will be much higher than 9A.
In case the RMS current is higher by a factor of 1.5 ... then the generated heat in the wires is higher by a factor if 1.5^2 = 2.25.
The temperature rise of the wires will be higher almost by the same factor.
Don't overload your house wiring .... don't risk fire.
In my eyes the PFC stage is the only solution
* according mains quality regulations (all the simple rectifier solutions may be illegal, check the regulations of your country)
* to keep RMS current close to 9A
* with low power loss soft start feature
Klaus
According to IEC 61000-3-2 Limits for harmonic current emissions (equipment input current ≤16 A per phase), professional equipment (defined as: equipment for use in trades, professions, or industries and which is not intended for sale to the general public) with a total rated power greater than 1 kW doesn't need to comply with harmonic current standards. It may be however necessary to achieve a permission by the supply utility to connect it. Presently most utility companies are ignoring harmonic current load of professional customers.Whether PFC is absolutely necessary or not, I'm not sure.
According to IEC 61000-3-2 Limits for harmonic current emissions (equipment input current ≤16 A per phase), professional equipment (defined as: equipment for use in trades, professions, or industries and which is not intended for sale to the general public) with a total rated power greater than 1 kW doesn't need to comply with harmonic current standards. It may be however necessary to achieve a permission by the supply utility to connect it. Presently most utility companies are ignoring harmonic current load of professional customers.
Regarding your design, I don't understand the purpose of input triac switch and particularly not the intended 120/240V configuration. If you have 120 VAC single phase input, you need a voltage doubling rectifier, as usually implemented in 120/240V PC power supplies.
Hi,
I'd use a PFC stage not only becasue of power factor correction or mains quality.
I'd use it because it solves the problem with charging high value capacitors.
There are many ready to buy ICs with relatively simple circuits.
Timing, inrush current ... can be easily adjusted. Low power loss, low heating.
And many really good application notes. I assume there are development boards available, too.
Klaus
We use cookies and similar technologies for the following purposes:
Do you accept cookies and these technologies?
We use cookies and similar technologies for the following purposes:
Do you accept cookies and these technologies?