C
CFoley1064
- Jan 1, 1970
- 0
Subject: inductor switch protection diode
A good rule of thumb is to make sure the current rating of the diode exceeds
the current going through the inductor when it's on. If you can, choose a
diode with a Peak Reverse Voltage (PRV) rating twice the voltage across the
inductive load when it's on. I would guess you're using 12 or 10AWG wire (30
amp) to the load. A similar size gauge going to the diode would definitely be
helpful, if you can.
I'd be a little more concerned about the turn-off for the FET. It looks like
you've got a driver that will turn on the FET quickly, but turn it off slowly
with the 10K pulldown. You might want to modify that.
Good luck
Chris
From: andy [email protected]-online.co.uk
Date: 8/4/2004 11:04 AM Central Daylight Time
Message-id: <[email protected]>
I'm using this circuit to control a short (1s) pulse of 14A through an
electromagnet coil. The coil is 3 separate windings of 3 ohms each, which
should give about 13.5-14A when switched on. I'm putting in a protection
diode to stop the inductor destroying the mosfet when it's switched off.
The question is, how do i work out the current rating for the diode and
the wiring to it? I'm using heavy 30A wire for the wires between the
battery, magnet, and mosfet, wired through an electrician's terminal
block, but i'm not sure if i need to do the same with the diode.
12V ---------o------------o-------
| |
|< |
On --| ----|
|\ - C|
| ^ C| Electromagnet
----o | C|
| | -----
.-. | |
10k | | | ||-+
| | | ||<- BUZ10
'-' o-----||-+
| |
---------o------------o--------
A good rule of thumb is to make sure the current rating of the diode exceeds
the current going through the inductor when it's on. If you can, choose a
diode with a Peak Reverse Voltage (PRV) rating twice the voltage across the
inductive load when it's on. I would guess you're using 12 or 10AWG wire (30
amp) to the load. A similar size gauge going to the diode would definitely be
helpful, if you can.
I'd be a little more concerned about the turn-off for the FET. It looks like
you've got a driver that will turn on the FET quickly, but turn it off slowly
with the 10K pulldown. You might want to modify that.
Good luck
Chris