Resetting SCR in this circuit
Resetting SCR in this circuit
(OP)
I'm trying to reset an SCR.....I know you have to drop the holding current below a certain point, but i cant figure out how to do that. Right now im just cycling the power, but i need to figure a way out to reset it electrically.
I built a braking circuit that shorts the motor leads thru a resistor.
----------------------|----------|
| | R2 |
| Z | |
PS ---- | ------ |
-- -------\ / M/Generator
---- | \ / |
-- | | |
| R1 | |
| | | |
-----------|---------------------|
---
-
R = 10ohm, 100W Resistor
R = 10ohm, 1W
M = 48V PMDC Motor
Z = 24V Zener
PS = 24V Power Supply
What I'm trying to do is build a braking system so when the PMDC motor starts becoming a generator that the SCR shorts and brakes the motor thru the resistor(R2). The motor runs off the PS(24V), but under certain conditions the motor will get driven and become a generator. When this happens i want to short the scr and use the braking resistor. Ive got the circuit to work, BUT i need a way to reset the SCR. Im at a standstill with this project, any help would be much appreciated.
I built a braking circuit that shorts the motor leads thru a resistor.
----------------------|----------|
| | R2 |
| Z | |
PS ---- | ------ |
-- -------\ / M/Generator
---- | \ / |
-- | | |
| R1 | |
| | | |
-----------|---------------------|
---
-
R = 10ohm, 100W Resistor
R = 10ohm, 1W
M = 48V PMDC Motor
Z = 24V Zener
PS = 24V Power Supply
What I'm trying to do is build a braking system so when the PMDC motor starts becoming a generator that the SCR shorts and brakes the motor thru the resistor(R2). The motor runs off the PS(24V), but under certain conditions the motor will get driven and become a generator. When this happens i want to short the scr and use the braking resistor. Ive got the circuit to work, BUT i need a way to reset the SCR. Im at a standstill with this project, any help would be much appreciated.





RE: Resetting SCR in this circuit
RE: Resetting SCR in this circuit
RE: Resetting SCR in this circuit
That's why SCRs are most often used in AC circuits where the 60 Hz waveform provides the periodic reset 120 times per second.
Using them in DC circuits is typically limited to protection functions (over voltage for example) where you'd expect the user to cycle the power switch to reset.
In other words, for your application, an SCR is probably not the right part to build the circuit around.
RE: Resetting SCR in this circuit
> your circuit as drawn shows the SCR also pulling current from the power supply, making it ineffective as a braking circuit
> your circuit shows nothing that disconnects the PS from the motor
> you show nothing in the circuit that turns on the SCR
> your circuit runs the risk of autotriggering the SCR if the power supply ramps too quickly or if there are excessive transients in the circuit
TTFN
RE: Resetting SCR in this circuit
Place a relay in the "holding current" path... when you want to reset the circuit, trip the momentary relay.
Dan - Owner
http://www.Hi-TecDesigns.com
RE: Resetting SCR in this circuit
Google "force commutation" for details.
Gunnar Englund
www.gke.org
RE: Resetting SCR in this circuit
RE: Resetting SCR in this circuit
RE: Resetting SCR in this circuit