High current mosfet repellant for rodents

[cupoftea]

Hi,
We will be switching on around 1000A's or so in to air cored coils of a few milliohms resistance, and very little inductance, just of a few turns.
So we will use paralleled MOSFETs and make the source a regulated voltage on a supercapacitor bank.
Do you agree we should best use MOSFETs? (cf IGBTs).

I realise MOSFET has a sensitive die, but IGBTs have too much Vce ON drop. In paralell i believe we can get the MOSFETs to survive?

Duty cycle is ON for 1 second every 10 seconds.

We need to measure the current aswell in testing it.....so we will use some kind of Hall sensor. Or possibly Fluxgate. Which
do you believe is best.?

 

[FvM]

Controlled voltage source or switched current are different topologies. In the former case you have to consider linear gate drivers, measures for equal current sharing, limited SOA in linear operation.

Apart form this unclear point, everything is possible, just a matter specification (operation voltage, acceptable voltage drop, accuracy).

 

[cupoftea]

Thanks, as you know, Sorry i didnt make clear....if we have a ~2 milliOhm load, and we regulate 2V across it, then we have 1000 Amps regulated.
Reg not have to be too tight, a few 10's of amps out is ok.

 

[D.A.(Tony)Stewart]

How do you plan to regulate limiting power dissipation in each device or regulate sharing during risetime other than crossing your fingers?
Who is designing the busbar for xx uohms and xx nH? Are you expecting a 2kW RF induction BBQ?

Ultrasonic beepers are far more efficient at repelling rodents.

 

[cupoftea]

Thanks, sorry i just discuss the "common" bits of it here...(not give away any industry secrets) as switching and distribution of thousands of amps is general knowledge (which i am also goggling like mad at the mo), but asking for short cuts here too if i may. Also, the IGBTs capable of thousands of amps seem to be rated for eg 1700V....but all we need is a few 10's of volts.

Does anyone know which industries are involved in switching and distributing thousands of amps?.....sorry its for 100ms max pulses, (not one second) separated by a few seconds.
The well and commonly known ones are.....

Electroplating
Radar jammers
Plasma power supplies eg medical surgical tissue cutters
Welding

Any more may i please ask? If i can find the users of "thousands of amps", then maybe can then find the equipment needed to do it.

Ive connected up a few electro plating power supplies before...but only 200A.....just used big heavy cable and dirty great ring terminals and a huge spanner to tighten it...oh, and the very important wire brush to clean the terminals.

Any heads up on the type of power supplies used to get "thousands of amps" much appreciated?....if i want high current i parallel lower current ones.....but havent done that to 1000A's......or eg the Full bridge with current doubler....but even that may shy away from 1000A's

 

[D.A.(Tony)Stewart]

You will need a bunch of 1mohm SiC FETs on a very low ESL Vgs to busbar heatsink with snubbers on your inductive loop across Vds. I have a friend who built such a busbar designed by U of T /ECE to switch > 10kW.

Switch speed cannot be slow even though gate Ciss is high I believe it must be <1ms for SiC BJT's in the 2 to 4 mohm range at 500A and probably faster for SIC FETs

So if you have a 1 mohm load you can estimate the switch bank RdsOn for 1% of load power to be 10 uOhm ! Otherwise you need a bigger SMPS

The best big low ESR caps for WPT chargers are from Germany and Japan I recall a few years ago and 800A BJT's exist.

"... voltage of 1200V and current rating of 20 – 50A perchip. First engineering samples based on 4H-SiC BJT powermodules with current rating of 800A (several dies in parallel)and voltage rating of 1200V from APEI Inc. have been testedin house.
(10) (PDF) Static and Dynamic Characterization of High Power Silicon Carbide BJT Modules. Available from: https://www.researchgate.net/public...ion_of_High_Power_Silicon_Carbide_BJT_Modules [accessed Feb 22 2024].

--- Updated Feb 23, 2024 ---

This looks to be a more efficient and reliable switch
low yen too

Then add your COTS PSU and " Bob's yer uncle."

 

[KlausST]

Hi,

I´ve worked with 0..2000V AC up to 3000A continus (1000kW max) systems. not paralleled water cooled SCRs. For the silicon industry, can work 24/7.
Not what you need, I guess.


Klaus

 

[cupoftea]

Thanks, please can you tell how many in parallel were used?
For a single non-isolated SMPS, what is the highest current they tend to go up to?
How do they manage the ripple current and switching node for those converters?
Also, what are the likely switching frequencies for eg a 1000-15000 Amp , single stage SMPS?

Also, what type of inductor cores do they use?
And also, what kind of noise mitigation measures do they take?

For example, a 4000 Amp SMPS, done with a single stage (no paralleling)......what kind of resistance do they get in the inductor?
I can't imagine say 1 milliOhm of resistance in such a thing being achievable?.
(eg say if it was a PWM Bridge controlled resistive load, with filter inductor.)

There are no pictures of these kind of things on the web. Someone gave me a doc, but no real specifics. No detailed circuit diagram or BOM. No pictures.
No scope shots.
I guess this stuff is deep industrial secret?

The following is just called a "rectifier"...so it just rectifys 3 phase?...not an SMPS.

I am doubtful there are many high frequency SMPS's which do 1000Amp in a single stage?

 

[cupoftea]

Thanks, on a related note does any one know where to source a 700uH inductor rated 1500A, and will suffer 120Apkpk ripple?
And must withstand voltage across it of some +150V then -150V at 1kHz.
Will only be conducting for 100ms every half hour.
DC Resistance preferably no more than 5millioms.
I assume we are talking an iron cored part here.

 

[BradtheRad]

all we need is a few 10's of volts.
...
Does anyone know which industries are involved in switching and distributing thousands of amps?.....sorry its for 100ms max pulses

Automobile engines start up on a few hundred Amperes, typically in less than a second. The 12V battery briefly sags a few volts. Cold temperature makes a larger demand on power draw.

Trucks often have 24V systems to do the same thing. I guess earth-mover vehicles vary in their voltage and Ampere requirements to start the engine.