Dead speed controller on Sieg SX2, can I just use an off the shelf VFD ?

[VicHobbyGuy]

So.. With the supplied information I've found this at about 1/4 the cost of a replacement unit, it looks like it meets the spec

That looks interesting. Hopefully it comes with a good user manual. I can't see the output voltage listed anywhere; is that an issue?

 

[BruceCook]

The thought cross my mind that the motor you have might not be designed for 230 volts input, the input to the original controller was 230 but there might be some or a lot of step down. One simple thing you could do to get an idea of what voltage the motor was designed for would be to set the belt drive to high and chuck up a corded drill to spin the mill over fast. Take a volt meter set it to AC and see what the output across two of the motor wires is. It should put out something like 80% voltage of what the motor was designed to run on.

Hope this helps

yeah, good point.

The label on the motor says 230v & looking at the circuit I see 230v coming in, through the filter board, the main switch & then directly into the IGBT collectors. When it tries to start I see a brief pulse of 230v on the emitter before it stops, so I'm confident that it is being run at 230v.

Added to that I don't see any regulator circuitry on the board between in input voltage & the IGBTs, the only regulator is for the control circuit.

 

[BruceCook]

yep, the user manual is less than stellar, I found a youtube video of a guy scroll down it . There are a number of configurations & questions about compatibility that I'm going to have to work through.
Other information I can find on the various controllers is spotty too.

Given what I've learnt, I think this is going to take some fiddling about and possibly a few failures to get working, all an interesting exercise, but not getting my milling projects done, I might throw this on the back-burner & just fork out for the OEM board & hope the new one doesn't fail too quickly.

Unfortunately I'm milling a new tailstock base for my lathe which is offline due to a brittle casting & I don't want to end up with a bunch of busted gear in my workshop.

Thanks for everyone's help, I've learnt a lot

 

[markba633csi]

It would be helpful if the electrical schematics of these controls were provided- my guess is there are liability concerns
"No user-serviceable parts inside" as the saying goes- but the right to repair shouldn't be determined only by the manufacturer

 

[DeltaCharlie]

yeah, good point.

The label on the motor says 230v & looking at the circuit I see 230v coming in, through the filter board, the main switch & then directly into the IGBT collectors. When it tries to start I see a brief pulse of 230v on the emitter before it stops, so I'm confident that it is being run at 230v.

Added to that I don't see any regulator circuitry on the board between in input voltage & the IGBTs, the only regulator is for the control circuit.

Looks like you have it under control. I was concerned the controller might have had a SMPS (Switching Mode Power Supply) built into it that stepped the voltage down. SMPS can be quite small and because the frequency they run at the step down transformer can be small too.

Please keep up posted if you figure something out.

 

[BruceCook]

For anyone who might be interested in where this got to, I have been managing to find some time to fiddle over the last month.

On a whim I purchased this controller for Ali Express, which turned out to be quite good. Documentation is sparse, but I was able to piece together the wiring based on a few listings of the part and an instructional video. https://www.aliexpress.com/i/1005005971819614.html

The next thing was to work out how many poles my motor had & by creating a position indicator circuit and wiring that and a pair of the coil legs to an oscilloscope, I found it was 4 - makes sense given the motor geometry.

I wired the controller up & got the motor running without too much bother.

The original issue remained however. I could get the motor running, but it would sometimes fail to start, and it sounded quite rough, got hot and this controller was throwing a code 4 error continuously.

Since I had the scope out I decided to look at the hall sensor inputs to see what they were doing & found that one of the sensors was stuck high instead of sending a pulse corresponding to the magnet passing. Pulling the back off the motor allowed me to access the transistors directly & confirmed the issue there.

Looking around for a replacement for that pickup assembly I was unable to find a direct match, but the transistors are easily accessible and I should be able swap a new one into place without issues.

So I've ordered replacements and am waiting for then to arrive & hopefully can put my mill back together.

Lessons learnt:
- Don't just jump to conclusions "It's got to be the controller" - this was noted as a failure point for a few others in forums, but I really should have investigated more deeply first.
- Pay attention when wiring up the power: don't plug the 240V AC into the brake resistor terminals. yes I did. Fortunately the nice manufacturer installed spare smoke into this unit and all I did was blow the brake tracks off the board (relay based braking) and didn't otherwise damage the board.

When I get this working I'll keep the new controller as it has a few nice features, such as soft start (the old stop/start worked by removing power from the board itself), reverse and MODBUS which I might fiddle with in future.

 

[markba633csi]

Cool- having a scope gives you tremendous troubleshooting advantages