Re: Newbie PSU calculations
Quote:
Originally Posted by
Soyb
Hi I am building a small gantry hobby router using 2 Y, 1 X and 1 Z closed loopback steppers,
Closed Loop Stepper Driver 0-7.0A 24-50VDC for Nema 23 Stepper Motor
Motor Specification
Part Number: 23HE30-5004D-E1000
Number of phase: 2
Holding Torque: 2.0 Nm(283.28oz.in)
Rated Current/phase: 5.0 A
Phase Resistance: 0.42 ohmsħ 10%
my calculations for the required power supply(s) is
4 motors x 5 amps each x 50 volts x 120% = 1200 watts
since not all the steppers will be running at full power at the same time I can reduce the requirement by 25% = 900 watts required
Are my calculations valid?
What is better, two switching power supplies, 450 watts or one 1000 watt?
https://www.ebay.co.uk/itm/402646721...r=672923118722
Any suggestions gratefully accepted
Thanks
I would go no less than 48v.
48V 800w will do it easily.
Generic 4 axis kits normally come with 2x 36V 350w supplies so the supply I suggest above is plenty :)
(36v is usually dissapointing).
Re: Newbie PSU calculations
Quote:
Originally Posted by
dazp1976
I would go no less than 48v.
48V 800w will do it easily.
Generic 4 axis kits normally come with 2x 36V 350w supplies so the supply I suggest above is plenty :)
(36v is usually dissapointing).
That would be a mistake for several reasons. First, 48V is too close to the drive's maximum voltage so any back EMF from the steppers when slowing down could damage the drives as it returns to drives and spikes above 50vdc.
Secondly, the regulated DC supply will cause problems for similar reasons, because steppers basically become dynamos when de-accelerating the voltage being feedback to the PSU will cause the supply to clamp and possibly shut down. This will be erratic and unpredictable and leads to all kinds of issues that not always obviously related to the PSU.
This is why Unregulated PSU is often used or better still toroidal transformer with smoothing capacitors for DC drives which will absorb any back EMF. Also, an unregulated toroidal setup allows lower power requirements, approx 60% of total stepper current, because of the way it works with the pulse modulation of the drives only needing power 50% of the time.
Using drives that accept AC input is becoming more popular because it removes the need for smoothing capacitors and rectifiers needed for converting to DC voltage, but still the use of an Unregulated PSU or toroidal transformer is required for the reasons stated above.
Re: Newbie PSU calculations
As a power electronics engineer developing switched mode power supplies and VFDs for some years, I have loads of PSUs in the garage to choose from but I've still used mains transformers and large electrolytics for my machines for the reasons JazzCNC gives.
Having said that, I've also got voltage clamps on my power supplies to limit any voltage surges during rapid deceleration of the machine. I notice that the LiChuan A4 servo drives I got recently for my current lathe conversion (thanks for the recommendation, JazzCNC) have built-in braking resistors that should take care of this to some extent in a similar way.
For my large machine, I bought a 3000VA site transformer from Screwfix (the steel housing version, not the yellow encapsulated type) and removed some secondary turns to reduce the output to 100Vac. This gives about 140Vdc on the cap and cost me less than £100.
I once made the mistake of combining a Leadshine switched mode PSU with a large electroloytic capacitor on one of my machines and found that it often wouldn't start up at the first attempt. This was because it saw the cap as a short circuit during startup and had a latching current limit. They don't all behave like that but a mains transformer is a bullet proof solution in comparison. And as JazzCNC says, during an overvoltage surge, a regulated PSU can latch off when you least want it to.
Re: Newbie PSU calculations
Quote:
Originally Posted by
JAZZCNC
That would be a mistake for several reasons. First, 48V is too close to the drive's maximum voltage so any back EMF from the steppers when slowing down could damage the drives as it returns to drives and spikes above 50vdc.
Secondly, the regulated DC supply will cause problems for similar reasons, because steppers basically become dynamos when de-accelerating the voltage being feedback to the PSU will cause the supply to clamp and possibly shut down. This will be erratic and unpredictable and leads to all kinds of issues that not always obviously related to the PSU.
This is why Unregulated PSU is often used or better still toroidal transformer with smoothing capacitors for DC drives which will absorb any back EMF. Also, an unregulated toroidal setup allows lower power requirements, approx 60% of total stepper current, because of the way it works with the pulse modulation of the drives only needing power 50% of the time.
Using drives that accept AC input is becoming more popular because it removes the need for smoothing capacitors and rectifiers needed for converting to DC voltage, but still the use of an Unregulated PSU or toroidal transformer is required for the reasons stated above.
You'll have to build him a toroidal DC then if tha's the case.
1: Even if you could get one in the uk it will be at stupid cost!!!!!. Importing coats even more!
2: Op likely (like me) wouldn't have a clue or the confidence to have a go at building one.
3: Not going to buy different drivers (again).
I'd have gone either DM860 type drivers and 60Vdc switched. Or ones that can take up to 70Vac straight off a base toroidal, all day long.
He has what he has!!!!!
Just turn the regulated down to 45V if you're that concerned.
I use DM860 and 60V right now and it's never failed me.
I've also recently got my first Lichuan A4 servo set (for spindle use), and I'll be going that route later down the line.
Overspent for the next 6 months!. :concern::whistle:
Re: Newbie PSU calculations
Toroidal and E core transformers don't behave much differently in this application, so I wouldn't get hung up on what transformer you go for. If you are into audio amps, the toroidals generate less of a stray magnetic field which can mean less risk of hum.
BTW, if you are bothered by the Bees Nest (TM) fans in the LiChuan servos, you can replace them with pukka Papst / NMB / Sanyo etc fans from CPC. I did this on mine and it has made the noise almost bearable.
https://www.youtube.com/watch?v=KbD27bVYns4
Re: Newbie PSU calculations
Quote:
Originally Posted by
Muzzer
BTW, if you are bothered by the Bees Nest (TM) fans in the LiChuan servos, you can replace them with pukka Papst / NMB / Sanyo etc fans from CPC. I did this on mine and it has made the noise almost bearable.
Cheers for that. The fan in the servo drive is pretty damn loud.
I was originally just going to mount it open on the wall next to the machine until I heard the noise.
I've bought a bigger control box so I can get everything else + the servo drive inside it together and see if that helps.
If it still bugs me, then I'll give the fan swap a go :thumsup:
I'm still early days bench testing atm with my old parallel bob & Mach3 to get a feel for it (and confidence with servo's).
I'm playing will all setups, PWM, step/dir, axis, relay & opto modules etc.
I have loads of time on my hands to fiddle, and learning a fair bit :)
I'll start on benching the UC300eth next week with Mach and UCCNC.
I want to get a good feel for UC and get the controller working perfectly with both softwares first.
Then I'll fit up the new box and put them to machine.
Got myself a stepperonline driver for my Z last week too. DM860T (takes up to 80Vac or 110Vdc).
Putting 80Vdc to it which should give my Z (nema34 1080oz) a kick up the a**e :smile:
Re: Newbie PSU calculations
Quote:
Originally Posted by
dazp1976
You'll have to build him a toroidal DC then if tha's the case.
1: Even if you could get one in the uk it will be at stupid cost!!!!!. Importing coats even more!
2: Op likely (like me) wouldn't have a clue or the confidence to have a go at building one.
3: Not going to buy different drivers (again).
Well, I'm not sure why you think got to import toroidal transformers.? There are plenty of places to buy them in the UK.
Building a DC toroidal PSU isn't difficult or rocket science and there are many examples on this forum, I would also gladly help you or anyone else if asked.
Quote:
Originally Posted by
dazp1976
I'd have gone either DM860 type drivers and 60Vdc switched. Or ones that can take up to 70Vac straight off a base toroidal, all day long.
He has what he has!!!!!
Why do you assume that.? he could just be asking because he's thinking to buy those drives.! (Which would be a mistake IMO, but that for the OP to decide)
Quote:
Originally Posted by
dazp1976
Just turn the regulated down to 45V if you're that concerned.
That doesn't get away from the fact it's still a Regulated PSU.
Quote:
Originally Posted by
dazp1976
I use DM860 and 60V right now and it's never failed me.
Just because it's working for you doesn't mean it's correct or advisable, fitting a regulated linear PSU is like playing Russian roulette and it will at some point give issues that may not always be obvious that they are coming from the PSU.
It doesn't cost much more to do it right the first time and it nearly always works out cheaper in the long run because as you stated above you don't need to "buy drives again" and the machine always works much more reliable, so why when going to so much trouble to build a machine would anyone spoil it for the little extra it takes to do it right is beyond my reasoning.!
Re: Newbie PSU calculations
I'm pretty sure if somebody can manage to wire up a functional CNC machine, then they can manage to wire up the required bits to create an unregulated power supply.
Re: Newbie PSU calculations
Quote:
Originally Posted by
m_c
I'm pretty sure if somebody can manage to wire up a functional CNC machine, then they can manage to wire up the required bits to create an unregulated power supply.
That's true, but the mistakes can be more energetic than in other parts of the machine. The first component to install should be the mains fuse, suitably rated for the job with an allowance for inrush. In the UK this can be in the plug-top but in other parts of the world a separate device is needed. This helps prevent backlash... from the rest of the family when the house goes black, taking Netflix with it.
Kit
Re: Newbie PSU calculations
Once you go over 13A in the UK, there is no fuse inside the plug. And even a nominal 13A fuse will sustain a lot more than 13A for extended periods before finally clearing. For instance, the std UK fuse cartridge would likely supply 26A indefinitely and the ring main behind the socket (typically a 30A type B) would also be happy to supply 50% over nominal almost indefinitely.
http://wiki.diyfaq.org.uk/index.php/...FusingTime.png
https://electricalapprentice.co.uk/h...t-mcb-or-rcbo/
Ideally you'd have a large incoming MCB and smaller, individual MCB circuit breakers for the different circuits inside the cabinet anyway. Like a big one for the VFD and smaller ones for the servos, control circuits, external coolant pump etc. This also allows you to isolate them during testing etc.
The function of the MCBs is to protect the wiring (and you) from fire risk etc during a fault, while allowing unimpeded operation otherwise. If you simply relied on one large MCB for all of the mains circuits, you could have a nasty fire / shock unless you use the same big fat wiring everywhere, including all the protective earths. Even then, the safety insulation used in transformers, power supplies, VFDs etc should be protected against large fault currents to maintain their integrity during a fault condition.
Re: Newbie PSU calculations
Quote:
Originally Posted by
Muzzer
Once you go over 13A in the UK, there is no fuse inside the plug. And even a nominal 13A fuse will sustain a lot more than 13A for extended periods before finally clearing. For instance, the std UK fuse cartridge would likely supply 26A indefinitely and the ring main behind the socket (typically a 30A type B) would also be happy to supply 50% over nominal almost indefinitely.
http://wiki.diyfaq.org.uk/index.php/...FusingTime.png
https://electricalapprentice.co.uk/h...t-mcb-or-rcbo/
Ideally you'd have a large incoming MCB and smaller, individual MCB circuit breakers for the different circuits inside the cabinet anyway. Like a big one for the VFD and smaller ones for the servos, control circuits, external coolant pump etc. This also allows you to isolate them during testing etc.
The function of the MCBs is to protect the wiring (and you) from fire risk etc during a fault, while allowing unimpeded operation otherwise. If you simply relied on one large MCB for all of the mains circuits, you could have a nasty fire / shock unless you use the same big fat wiring everywhere, including all the protective earths. Even then, the safety insulation used in transformers, power supplies, VFDs etc should be protected against large fault currents to maintain their integrity during a fault condition.
When it comes to a DC power supply for steppers etc, say example a switched. We'll go a little overboard here.
Lets say you have a 60Vdc, 16.6A, 1000W big unit. This is it's max OUTPUT.
It doesn't mean that it uses 16.6A from the mains and needs a breaker.
You're INPUTTING 240Vac to it, so 1000W on 240Vac is actually 4.16Amps.
If you're building a control box with these types in you'd prob only want a 6A or 10A for the above size supply.
You don't see a 1000W heater or toaster or kettle needing a MCB.
Something like that anyway.
Re: Newbie PSU calculations
If you have a 16A CEE Commando plug, you've probably got a 30A MCB behind it. As you say, a 1000W PSU probably only needs a few amps, so you'd want to use fairly spindly wires and a 6A MCB. However, if you have a 3kW spindle motor, you'd be wanting a 16A MCB and fatter wire.
The main difference between an MCB and a fuse is that the MCB can be reset easily - and can also be used as a switch. If you don't like MCBs, fuses are good but you should fit something. You don't see a 60W laptop PSU supplied with a 13A plug....
I've got a fair idea what I'm talking about when it comes to PSUs and VFDs, as designing them has been my job for the last 36+ years ;-)
Re: Newbie PSU calculations
Quote:
Originally Posted by
dazp1976
When it comes to a DC power supply for steppers etc, say example a switched. We'll go a little overboard here.
Lets say you have a 60Vdc, 16.6A, 1000W big unit. This is it's max OUTPUT.
It doesn't mean that it uses 16.6A from the mains and needs a breaker.
You're INPUTTING 240Vac to it, so 1000W on 240Vac is actually 4.16Amps.
If you're building a control box with these types in you'd prob only want a 6A or 10A for the above size supply.
You don't see a 1000W heater or toaster or kettle needing a MCB.
Something like that anyway.
And you totally missed the point Muzzer was raising.
Plus it's not like it's not unknown for heaters, toasters, and kettles to go up in flames.
Just because the accepted default fuse size is 13A, doesn't mean it's the ideal size to use.
Re: Newbie PSU calculations
My workshop / man cave has a 30A supply split in to a lighting circuit and 2 16A MCB ring mains. The machine I am building is a 'light weight' CNC gantry router for cutting wood and possibly some aluminium (very slowly).
See http://www.mycncuk.com/threads/14590...-Gantry-Router
I am planning to use a 1 KW kress spindle and 4 x 5A closed loop stepper motors, so the electrical demand is quite low. I was going to rely on the consumer unit for my main protection and just have a No Volt Relay, On/Off switch and Emergency Stop on the mains side of the machine.
Electrics is not my thing, but I haven't killed myself yet.........:smug:
Is it worth putting a 6A MCB in the enclosure?
Re: Newbie PSU calculations
MCB's cost like £5 each and glass fuses like 50p so it's crazy not to use them IMO.
In my control boxes, I fit 3 x MCB's one for the Main toroidal PSU, VFD, and low voltage PSU's, the drives each have their own slow-blow glass fuse. So For less than £20 we are protecting over £400 to £500 worth of electronics and in worst-case scenario's, which happen more often than people realize property and life which are quite honestly priceless.!! . . . .Don't be stupid people, fit fuses and be safe.
Re: Newbie PSU calculations
Quote:
Originally Posted by
JAZZCNC
MCB's cost like £5 each and glass fuses like 50p so it's crazy not to use them IMO.
In my control boxes, I fit 3 x MCB's one for the Main toroidal PSU, VFD, and low voltage PSU's, the drives each have their own slow-blow glass fuse. So For less than £20 we are protecting over £400 to £500 worth of electronics and in worst-case scenario's, which happen more often than people realize property and life which are quite honestly priceless.!! . . . .Don't be stupid people, fit fuses and be safe.
Actually Jazz.
That brings me to a question for you.
My A4 servo requires a 30A breaker but unless I import something (again), all I see around are 32A.
I want to double the 32A mcb in-line with 30A glass fuse.
Where do you get your glass fuse holders from?. Want a Din mounting type.
It's either that or drop down to a 25A mcb and hope it don't keep tripping off.
Already got some of the other mcb's and some AC relays for each to activate an estop if any trip off.
Cheers.
Daz.
Re: Newbie PSU calculations
Don't worry about the difference between 30A and 32A. Neither of them will trip for at least a few seconds even at 50-60A load, so the difference is academic. However, they still trip faster than a cartridge fuse - due to a teensy-weensy little assembly error when I made some recent changes to my control box, I put an earthed bolt through the incoming mains cable. 32A ring main MCB tripped pretty much instantly, but the 13A fuses in mains cable and extension lead stayed intact. I suppose the MCB saved the fuses!
Re: Newbie PSU calculations
Quote:
Originally Posted by
dazp1976
Where do you get your glass fuse holders from?. Want a Din mounting type.
Like Neale says don't worry about the difference between 30A and 32A and even 25A won't complain until you would want it to anyway.
The Cartridge type fuses you can buy from any decent electrical supplier like RS and there are plenty on eBay also.
