Thread: Help please! VFD SCM Braked Motor

Photo of the motor plate.

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Oh, and this was also inline from (I assume) the transformer or rectifier or whatever to the motor -

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And here's one of the machine so it's not all electronics photos.

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Cheers, Dom

Hi Dom,

I have a Spindle Moulder that is braked and hard to start, my shed only has 32 amp's and I built a RPC using a 10HP slave motor, so I should be good for 5HP machines (50% of the 10HP) but the Spindle Moulder is 5kw (6.7HP) and with the brake the electric magnetic contactor will not hold long enough to get the machine started, so what I have to do is start my panel saw (old 1988 Altendorf F45) which is wired from the factory with a turn switch that the first turn puts it in Star (once up to speed) second turn puts it in Delta. Once the panel saw is running I can start the Spindle Moulder, this works because when a 3 phase motor is running within a circuit it acts like a generator adding more capacity to the circuit, so my 10HP slave motor now as the 5HP from the panel saw giving 15HP and therefore allowing 50% 7.5HP to start my Spindle Moulder. When the Spindle Moulder is running I turn off the panel saw.

I went down the route of a RPC because I have a number of 3 phase machines and I can run more than one machine at a time with my RPC, whereas I would have had to have a VFD for each machine because VFD are only good for one 3 phase motor.

With your issue I would wire your machine to the VFD as though you were wiring it directly to a 3 phase supply, your VFD should be able to cope with the initial start up AMP's thus letting your machine work like normal, if it does not then consider a RPC, I build mine myself using a Welder as a step up transformer.

Cheers Nigel

Originally Posted by Camelot

With your issue I would wire your machine to the VFD as though you were wiring it directly to a 3 phase supply, your VFD should be able to cope with the initial start up AMP's thus letting your machine work like normal, . . .

I wouldn't recommend this. Unless it's completely disconnected the integrated Brake is highly likely to damage the VFD and even the motor. VFDs require a direct connection between them and the motor, no control switches and definitely no braking. The headaches come if the machine is every turn of under load there will be a loud BANG and some smoke will escape.

The brake works by imposing a load on the motor, Rectified AC to DC is used at slower speeds to further slow and then lock motors. This is also how some VFD brakes work but they must be in total charge of the process and it cannot be done by external circuitry.

If you want to use VFD you'll have to bypass all the wiring and use a simple 3P motor.
I suspect this will mean completely void your warranty.

BTW an e-brake can be added to a VFD (provided it has incorporated braking circuitry) for just a few $$, the last braking resistor I bought cost about $15.
If you go this route make sure the VFD has the built in circuitry as this is not always standard, but it only costs a few $$$ more.

An RPC is sounding like a better option as you will be able to keep your warranty but seeing as you are not going to be able to do this yourself be prepared to spend big $$. Might even be cheaper to get 3P power installed.

It's a real pity you did not investigate all this before you purchased.

There probably is away to disconnect the brake, rewire/modify existing switches, and add some interlocks, so they control a VFD directly. My guess is it would be a significant rewire, again voiding the warranty. Due to the very high risk nature of this approach it's not the sort of advice one should deliver, or accept, via the internet. It would ned to be looked at in detail by a competent electrical fitter. again more $$$$

Originally Posted by BobL

I wouldn't recommend this. Unless it's completely disconnected the integrated Brake is highly likely to damage the VFD and even the motor. VFDs require a direct connection between them and the motor, no control switches and definitely no braking. The headaches come if the machine is every turn of under load there will be a loud BANG and some smoke will escape.

The brake works by imposing a load on the motor, Rectified AC to DC is used at slower speeds to further slow and then lock motors. This is also how some VFD brakes work but they must be in total charge of the process and it cannot be done by external circuitry.

If you want to use VFD you'll have to bypass all the wiring and use a simple 3P motor.
I suspect this will mean completely void your warranty.

BTW an e-brake can be added to a VFD (provided it has incorporated braking circuitry) for just a few $$, the last braking resistor I bought cost about $15.
If you go this route make sure the VFD has the built in circuitry as this is not always standard, but it only costs a few $$$ more.

An RPC is sounding like a better option as you will be able to keep your warranty but seeing as you are not going to be able to do this yourself be prepared to spend big $$. Might even be cheaper to get 3P power installed.

It's a real pity you did not investigate all this before you purchased.

There probably is away to disconnect the brake, rewire/modify existing switches, and add some interlocks, so they control a VFD directly. My guess is it would be a significant rewire, again voiding the warranty. Due to the very high risk nature of this approach it's not the sort of advice one should deliver, or accept, via the internet. It would ned to be looked at in detail by a competent electrical fitter. again more $$$$

Thanks Bob,

Yeah, I called the VFD supplier and an Electrician and they said it should be all good so I figured it would be simple enough.

Is the brake on the motor a mechanical brake that is released when a current is applied or is it some kind of electrical brake? I assume the former. If so, is it likely to be able to be removed and re-installed later if desired?

I asked the VFD supplier (Connon Motor) if I should buy their 7.5kW VFD or 5.5kW to run the 5kW motor and he said the 5.5kW would be fine. Should I have bought the larger VFD? I had a 40Amp 240V single phase circuit to the VFD.

Thanks a lot for the help.

Cheers, Dom

Originally Posted by DomAU

Thanks Bob,

Yeah, I called the VFD supplier and an Electrician and they said it should be all good so I figured it would be simple enough.

It sounds like they made too many assumptions. There are not many sparkies out there that understand VFDs and their complications. You would have been better off going to an industrial electrical fitter.

Is the brake on the motor a mechanical brake that is released when a current is applied or is it some kind of electrical brake? I assume the former. If so, is it likely to be able to be removed and re-installed later if desired?

I doubt it - its most likely to be a self-inducing electromagnetic brake of some kind. One of my Italian cousins make these sorts of motors mainly for large forklifts and loaders. Being electrical it may be possible to just disconnect it but you really need to know what you are doing as it may have interlocks built into it that disable the motor and you don't what to be leaving leads dangling around..

One thing that really concerns me about applying any 240V VFD 3P output to the plug of that machine is that is uses an internal secondary transformer with all manner of different output voltages used for machine control. If a 240V VFD output is supplied to that transformer there's no guarantee the transformer will even work, and even if it does all the output volts will be wrong for the machine.

You could try an Ecogoo VFD which are 240V SP input and 415V 3P output but I won't guarantee it will work because of all switches and other gear between the plug and the motor. That motor will almost certainly have its thermal/overcurrent protection built into all that switchgear. When using a VFD, all those switches and protection MUST be bypassed because if the protection kicks in from say a machine jam or a motor overheat, the resulting current surge will cook the VFD and can also damage the motor.

When using a VFD, it's the VFD that provides all those protections both to the motor and also to itself but there must be a hard connection to the motor so all this can work.

Be very careful, 415V is not to be treated lightly, there are very high risks of lethal voltages and fires - maybe not immediately, but later when you are tucked up in bed.

Hi Bob,

If a VFD needs to talk directly to the motor then they are useless on these types of modern machines, best to use a RPC, you should be able to get a professionally built one second-hand for under $3K, 3 phase can cost up to $10K.

The other option is to change the machine for the less powerful single phase version, which looking on the net seems to do the job.

Originally Posted by BobL

It sounds like they made too many assumptions. There are not many sparkies out there that understand VFDs and their complications. You would have been better off going to an industrial electrical fitter.


I doubt it - its most likely to be a self-inducing electromagnetic brake of some kind. One of my Italian cousins make these sorts of motors mainly for large forklifts and loaders. Being electrical it may be possible to just disconnect it but you really need to know what you are doing as it may have interlocks built into it that disable the motor and you don't what to be leaving leads dangling around..

One thing that really concerns me about applying any 240V VFD 3P output to the plug of that machine is that is uses an internal secondary transformer with all manner of different output voltages used for machine control. If a 240V VFD output is supplied to that transformer there's no guarantee the transformer will even work, and even if it does all the output volts will be wrong for the machine.

You could try an Ecogoo VFD which are 240V SP input and 415V 3P output but I won't guarantee it will work because of all switches and other gear between the plug and the motor. That motor will almost certainly have its thermal/overcurrent protection built into all that switchgear. When using a VFD, all those switches and protection MUST be bypassed because if the protection kicks in from say a machine jam or a motor overheat, the resulting current surge will cook the VFD and can also damage the motor.

When using a VFD, it's the VFD that provides all those protections both to the motor and also to itself but there must be a hard connection to the motor so all this can work.

Be very careful, 415V is not to be treated lightly, there are very high risks of lethal voltages and fires - maybe not immediately, but later when you are tucked up in bed.

Oh man. It seems i've really stepped in it this time. I feel kinda sick tbh.

So it seems that the only reasonable cost option at this point is to buy another three phase motor that can run 240V Delta but without a brake and swap it out. I hope mounting points and shaft sizes etc are relatively common for induction motors.

Would the VFD or the circuit breaker not prevent a motor overload situation? Or do there need to be fuses to achieve that protection?

This really sucks.

Thanks for all the help.

Man, I got this machine so I could more confidently take on a larger job and so couldn't wait until November for a single phase version of the machine to come in. It was a lot of cash for me so i'm really hoping I can find a reasonable resolution.

Assuming you can find the techincal details of the brake, it might be able to be permanently bypassed? Just a thought and i'm not a sparky.

As an alternative, could you get a phase changer and run it off that? Will cost you a bit more but they regularly come up for sale on gumtree or similar and at least you will not possibly void any warranty on your beautiful new SCM machine. Phase changers are typically cheaper than getting 3 phase supply installed plus you can use it on future 3 phase purchases.

Home Page | Phase Change Converters

I've used 4kw single phase on a 410mm wide SCM combo with the Xlyent cutterhead it is plenty of power if you can find a simple single phase solution.

Phase changer are in Victoria you could try your luck at 'hiring' one to get your job done at least? They might have a floor model that is suitable.

Originally Posted by DomAU

Oh man. It seems i've really stepped in it this time. I feel kinda sick tbh.

So it seems that the only reasonable cost option at this point is to buy another three phase motor that can run 240V Delta but without a brake and swap it out. I hope mounting points and shaft sizes etc are relatively common for induction motors..

Yep - that can become a major exercise, at times much more awkward than the electrical side of things because of the range of MW gear needed. I've swapped out many motors and found shafts and mounting points can become major PITA and is one reason I've ended up with so much metal working gear (like full sets of metric and Imperial keyway cutters, and metal reamers for making precision bore holes etc.

A few years back I replaced a 3HP SP DC donk with a 4HP 3P motor sos I could run it under a VFD - the mechanical side of things involved removing the motor rotor and turning it down from 28 to 24 mm to suit the impeller bore and then cutting a new keyway into the end. Luckily I was able to get master machinist Anorak Bob to do this for me as there would have been a high likelihood of me botching this.

With your machine being so new it should be a standard fitting
BUT
I would not put a cheap motor into such a nice machine, I would look for something of commensurate quality.

Would the VFD or the circuit breaker not prevent a motor overload situation? Or do there need to be fuses to achieve that protection?

Circuit breakers are there to protect the physical circuit, machines are supposed to look after themselves. Most 3P motors at a minimum uses a current overload limiter that can be adjusted with a screwdriver or similar to suit the motor/use. Usually these are found inside the large contractor switch boxes that are used on 3P motors. Most (but not all especially cheap) VFDS have this built into their operation - but you should not use both the programmable VFD current limit and the original contactor switch with current limiter that comes with a machine.

Some motors, usually SP also have a crude thermal cut out switch on them, the ones you "push to reset". These also need to be removed. Anything that manually or auto cuts the power (especially under load, which is often the reason these protections kick in) between the motor and VFD s a no-no. A large transient results which blows caps and IBGTs in the VFD. There are ways to interlock and get around the switches but the original auto protections must be removed.

Man, I got this machine so I could more confidently take on a larger job and so couldn't wait until November for a single phase version of the machine to come in. It was a lot of cash for me so i'm really hoping I can find a reasonable resolution.

It's sounds like renting an RPC is the way to go short term. You can stuff around for ever on the VFD thing. How far away os your 3P power?

Be very wary about any advice you receive on the internet (including from me) about this stuff as it is generally very poorly understood. If you get a good sparky to do it presumably if it breaks he/she is responsible and should set it right?

Originally Posted by Camelot

Hi Bob,

If a VFD needs to talk directly to the motor then they are useless on these types of modern machines, best to use a RPC, you should be able to get a professionally built one second-hand for under $3K, 3 phase can cost up to $10K.

The other option is to change the machine for the less powerful single phase version, which looking on the net seems to do the job.

I doubt he can even just swap out the 3P for an SP without significant rewiring.

VFDs are great if you know what you are doing and can do your own sparky and mechanical work.
I've got 9 VFDs running in my shed. Most of them are $100 cheapies running on small machines.
All up still cheaper than an RPC or 3P power.
Plus there's much more to VFDs than just being able to use them as s source of 3P power.
Even if I had 3P power in my shed I would still put about half those machines on a VFD.

I have been thinking of the cheapest way to run your machine based on what you have already bought and you could just simply disconnect the wires from your motor and put terminal blocks and insulation tape around them (you will not need them anymore), next mount your VFD somewhere on your machine, then run your 40 AMP supply to the VFD and in turn run from your VFD outputs L1,L2 & L3 directly to your motor. You will be able to Start/Stop your machines motor directly with the VFD and also a 5.5 Kw VFD should come with lots of programable options including the ability to brake your machines 3 phase motor.

Also thinking about it further, you could still use your machines on/off switch, you just need to disconnect the wires from this switch that are going to the all the things that are causing you problems and forget they are on the machine (just make the wires safe) then from this switch run wires to your VDF, your VDF will have inputs allowing it to be operated from a normal on/off switch, which is what you have on your machine. Once your VFD is programmed correctly, e.g. correct RPM for your cutter block, then it does not need to be messed with again and can simply be controlled via your machines on/off switch.

Hi Dom, not really helpful now but I own the table saw from this (elite) line of SCM in single phase.
When I was buying I asked about the 3 phase version and VFDs and was told point blank don't do it, plan on a phase converter if no hard wired 3 phase available, apparently they'd had a number of dramas with people trying this over the years.
I've not found the single phase version under powered for what I do.

Originally Posted by Camelot

I have been thinking of the cheapest way to run your machine based on what you have already bought and you could just simply disconnect the wires from your motor and put terminal blocks and insulation tape around them (you will not need them anymore), next mount your VFD somewhere on your machine, then run your 40 AMP supply to the VFD and in turn run from your VFD outputs L1,L2 & L3 directly to your motor. You will be able to Start/Stop your machines motor directly with the VFD and also a 5.5 Kw VFD should come with lots of programable options including the ability to brake your machines 3 phase motor.

That was the plan and is what i'd still like to do. The only issue is the motor brake on the motor which I believe to be electromagnetically released. The machine looks to have a transformer and rectifier to convert the incoming line voltage into DC voltage (but looking at the rectifier I can't figure out what voltage is needed in and what is coming out - looks like 110V DC) which I assume is to disengage the brake by providing power to it (it is otherwise on with no power supplied) and believe this is also why there is something that looks like a delay circuit/box in the machine - to ensure the motor brake is off before the motor can be turned on. In any event, the sticking point is figuring out how to either provide the right power to the motor brake to disengage it, or physically remove it from the motor if possible. For the former I guess i'd need to run a second 240v supply line through a rectifier and a switch or relay so that I could energise that before switching on the motor with the VFD.

Cheers, Dom