Show us your VFD conversions/installations

[W-Cummins]

Interesting, never seen those form factor of SSR used in a cabinet. Do they have heat sinks behind them?

Well I guess you could say "kind of" they are attached to metal din rail mounts that probably provide some heat sinking but not much... Also there is no thermal compound under them....

No. Guessing not much load on them.

Bingo! So the relays are 240 vac @ 10 amps so I'm sure at full load and max switching they will get hot, however neither is the case here. These drive small 120v pneumatic valves, and they have a super low duty rating like 5 seconds out of 60! It looks like the oem dust controller has a range of up to like 3 seconds max. So if you look closely at the HMI display you will notice a cool down timer. The timer is used to prevent the cleaning "cycle" from repeating more than once per 60 seconds, I currently have it set to 1 second, with 1 second between the banks ( to allow the air to refill the "air tank" mounted on the collector) so it's over in 8 seconds then waits 60 more. Also under "Normal" operation this will probably be a rare event as I assume that the thing will not need to clean the filter banks more than a few times per day??

 

[Beerhippie]

Well I guess you could say "kind of" they are attached to metal din rail mounts that probably provide some heat sinking but not much... Also there is no thermal compound under them....

Bingo! So the relays are 240 vac @ 10 amps so I'm sure at full load and max switching they will get hot, however neither is the case here. These drive small 120v pneumatic valves, and they have a super low duty rating like 5 seconds out of 60! It looks like the oem dust controller has a range of up to like 3 seconds max. So if you look closely at the HMI display you will notice a cool down timer. The timer is used to prevent the cleaning "cycle" from repeating more than once per 60 seconds, I currently have it set to 1 second, with 1 second between the banks ( to allow the air to refill the "air tank" mounted on the collector) so it's over in 8 seconds then waits 60 more. Also under "Normal" operation this will probably be a rare event as I assume that the thing will not need to clean the filter banks more than a few times per day??

I mount those Croydon SSRLs directly to the aluminum backplate with a little compound on them and call it good enough. They seem to do fine, even with a pretty good load on them.

I have a few that are mounted in regular watertight single-gang outlet boxes. I use a piece of copper plate (flattened out type L pipe) that fits just inside a blank aluminum cover. Those also work fine.

One thing to be aware of, if you're not already--is that SSRLs tend to fail to the closed state. In some applications, this can be a real problem. I've rarely had any problems--and there are dozens in use around the brewery--but it has happened twice that I recall.

 

[whateg01]

...One thing to be aware of, if you're not already--is that SSRLs tend to fail to the closed state. In some applications, this can be a real problem. I've rarely had any problems--and there are dozens in use around the brewery--but it has happened twice that I recall.

When the makerspace built a powder coat oven, they used a ssr. It's failed a few times now. It's better after I convinced them to get the control box away from the side of the oven where it was cooking everything in the control box but it's still failed once since then. In this case, I am trying to convince them to add some sort of thermal runaway monitoring. I'm not sure what i would do in op case, but I think I would want something to back it up in case it fails. As stated here, it will fail closed.

 

[Beerhippie]

When the makerspace built a powder coat oven, they used a ssr. It's failed a few times now. It's better after I convinced them to get the control box away from the side of the oven where it was cooking everything in the control box but it's still failed once since then. In this case, I am trying to convince them to add some sort of thermal runaway monitoring. I'm not sure what i would do in op case, but I think I would want something to back it up in case it fails. As stated here, it will fail closed.

For those who aren't fluent in electricalese, "closed" means ON.

 

[old_smokey]

Not sure if this thread is still active... but here it goes.

I got a deal on a cheap 4kw VFD. It's a Mollom G75-2T-4G-B, rated to 5hp.
I want to use it on a table saw that has a 3hp 3-phase motor.

This will be my first VFD conversion, so I'm learning a lot. I want to run through how I intend to wire this up and see if the collective Garage Journal brain-trust has any advice.

My VFD is over-sized for my motor. My understanding is that the VFD input wiring should be sized to the VFD, not to the motor being driven. My VFD says it has a maximum output of 17 amps. There isn't a listed maximum input current, but using math, I can estimate it would be around 29-30 amps (17 x 1.732).

I've read that it's common to upsize the breaker and the supply wire by 125% of the VFD max current, which puts me just under 37A. So, a 40A circuit would be required. I plan to run a 40A #8 240V circuit into a surface-mounted wall receptacle next to my panel, then use a power cable to send supply into a NEMA enclosure.

From there, I'll pass through a two-pole 40A breaker again (redundant, but I thought it would be nice to have a shut-off right in the box), then to a 40A-rated contactor (so I can remotely switch power to the VFD on/off).

Then each hot leg will pass through a 40A 10x38mm fast-acting fuse, like a KTK-40. Probably will use a DIN-rail mounted fuse holder for this.

Then I'll use a 40A-rated noise filter, and finally into the VFD itself.

The contactor I'm planning to use will likely have a 24VAC coil, so I'll need to add a transformer to get control power. The transformer will pull power to its primary winding off the noise filter lugs, and I'll add an in-line 1A fuse. I'll control the contactor windings with a simple switch somewhere under the table saw. This will let me shut off the entire enclosure when I'm not using it... which will be often.

Oh, and I want to add a fan. I've got a nice 12V DC fan handy, and I will add a 12v DC power supply easily enough.

Am I missing anything? Making any big mistakes? Wasting money?

 

[paulsomlo]

Do you have 3 phase power at your panel? I looked up the model # on that and found a user's manual: