I have two Cutler Hammer soft starters. Both with two different status lights. One red (showing fault) and one green (showing no fault) but both have NO output. Both are over 5-7 years old. A brand new soft start was purchased/installed and worked perfectly. I currently cannot power these on in my shop because I do not have access to 600V.

I have tested puck style SCRs in the past but it has been over 5 years ago. I do remember them usually shorting.

The SCR part number is T560N16TOF. I've attached the datasheet.

I have applied significant force to many of these SCRs using a hand clamp and I am getting "OL" between the cathode (-) and anode(+) when I believe I'm supposed to get a diode voltage drop (0.6Vish). I am trying to determine for sure if these are bad before I order new ones as they are $100+ each and there are a total of 12 SCRs.

If anyone has any experience with these puck SCRS, I would greatly appreciate your input.

Thank you,

Anna

 

An SCR should read open circuit between anode and cathode. Gate to cathode should look like a diode.

 

It is generally easy to test SCR's with low voltage AC and a lamp load.
Max.

 

An SCR should read open circuit between anode and cathode. Gate to cathode should look like a diode.

Thanks for the reply. Is that the case for this type of SCR? Please refer to this video. She is measuring 0.4V between the anode to cathode when compression is applied.

 

What she is testing is a diode not an SCR.

 

How come all the references and the data sheet pertain to 'Thyristor'??
Max.

 

An SCR should read open circuit between anode and cathode. Gate to cathode should look like a diode.

Some SCRs have an internal reverse diode, so reverse conduction may not necessarily be a fault.

Can't remember when I last saw one of those - but there's a few lurking out there.

 

How come all the references and the data sheet pertain to 'Thyristor'??
Max.

Hi Max,

Yes, you are correct it is referred to as a Thyristor. I may have messed up the wording a bit because whenever I search for this part online, distributors have it listed under "SCR modules".

So I guess I'm just not how to properly measure this thing to determine if it's good or bad. I don't think the typical lamp load test will work on this because it does not have a collector or emitter. Just anode, cathode and gate.

 

Hi Max,

Yes, you are correct it is referred to as a Thyristor. I may have messed up the wording a bit because whenever I search for this part online, distributors have it listed under "SCR modules".

So I guess I'm just not how to properly measure this thing to determine if it's good or bad. I don't think the typical lamp load test will work on this because it does not have a collector or emitter. Just anode, cathode and gate.

Can't see why a lamp load test wouldn't work, but the holding current might be more than some typical PCB SCRs can handle. A car headlamp bulb would eliminate doubt. Running from DC; you should be able to trigger it on and it stays on, AC commutates the SCR at every zero crossing, so you have to maintain gate current as long as you want it to stay on. Without an internal diode; the bulb only gets half cycles and isn't fully bright. With the diode; the bulb is half bright with no gate current and comes up full bright when you trigger it.

 

Can't see why a lamp load test wouldn't work, but the holding current might be more than some typical PCB SCRs can handle. A car headlamp bulb would eliminate doubt. Running from DC; you should be able to trigger it on and it stays on, AC commutates the SCR at every zero crossing, so you have to maintain gate current as long as you want it to stay on. Without an internal diode; the bulb only gets half cycles and isn't fully bright. With the diode; the bulb is half bright with no gate current and comes up full bright when you trigger it.

Hi Ian,

Thanks for your input. I've never done this type of test before for an SCR. I am able to simulate this using DC? Would 12V suffice? What type of lamp exactly? I unfortunately don't have a car headlamp accessible.

 

The holding current for this SCR is up to 300mA so you need some load that will take at least this much current so that when you trigger it it will stay switched on.

 

I always use the standard test on mine with AC, secondary from suitable transformer, 100Ω resistor from A to G and lamp on K to the other side of AC power.
Switch G on/off.
Max.

 

I always use the standard test on mine with AC, secondary from suitable transformer, 100Ω resistor from A to G and lamp on K to the other side of AC power.
Switch G on/off.
Max.

Perfect. Thanks max!