Hi,
I not sure all the project parameters are pertinent to the supply design,
but here what I can give you:
Injector Coil DC Resistance: around 1 ohm
Injector Coil Inductance: Unknown
Injector Coil Pulse width: Variable between 50 microseconds and 5
milliseconds
Injector Coil Pulse frequency: Variable between 0 to 60 Hz
The motor use 6 injectors. They are pulsed in sequence, one by one.
The 6 injectors have a common path to the +120Vdc supply. They are return to
ground using a power mosfet drive by a computer. (This is very similar to
industrial unit).
Our prototype used a very typical 120Vac input power supply, using a simple
transformer/bridge/capacitor design powered from the outlet. We add a 10
ohms power resistor in series with the +120Vdc to prevent the bridge from
exploding in case of short, but this limit the current and heat up a lot.
We tried to use a commercial power inverter (400watts 13.8Vdc to 120Vac) to
drive the 120Vac transformer to run the device from the 13.8Vdc power
source. This is not working very well; the inverter is not powerful enough.
We did not try with larger inverter. In any case, this concept is far than
be efficient, and end up to being too voluminous to be used later.
I did try to use the power inverter as supply, but as mention we end up with
170Vdc. I modified the unit removing the DC to AC section and use only the
13.8Vdc to 170Vdc section. I also modified the loop back to lower the output
at 120Vdc, but this is too limit for the unit transformer, it end up
unstable and I still have no current limit protection. The prototype
explodes a couple of time during test. The transformer should be modified,
removing a few secondary turns, but it's impossible to rewire it without
destroying it.
Looking at industrial units, I know they use something similar to a boost
regulator. They use a PWM chip (unmark), a coil and a 220uf 160Vdc
capacitor. The circuit is a bit complex, build on a multilayer PCB and
difficult to reverse engineer. In any way, I do not wish to copy any
proprietary design.
I need the short protection, in case one of the mosfet short, this can
append. Also the end users are not very prudent to protect the circuit. They
often short the coils or let wires touch the frame and so on. So it must be
build to endure rough treatment.
Bye
Jacques
Yea... you forgot to mention what resistance. And inductance too. Any
peculiar turn-on-surge current? Exactly how long are they on for?
Tim
You might be able to adapt a scheme such as shown in...
http://www.analog-innovations.com/SED/HammerDriver_RevD.pdf
You need to measure the inductance of your injectors, then I could run
the numbers.
...Jim Thompson
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