Factory circuit breakers in business park in Australia (Vic) - Page 1
Forum section: electronics / general

author: loki42
author_rank: Frequent Contributor
timestamp: July 02, 2024, 09:37:43 am
content: In my wisdom I have bought a lathe that requires me to upgrade my breakers. The lathe has a large external transformer, it transforms Australian 3 phase (400V) to Japanese 3 phase voltage (200V).Currently the set up that the electrician has installed is:Machine Main Breaker: 225A (Japanese voltage) -> Machine Breaker on the Panel: 50A (D50) (AU Voltage) -> Factory Main Isolator on the Panel: 40A (C40) -> Building Main Isolator outside cabinet near street: 40A (C40).The jump from D50 to C40 here doesn't make sense to me.The main factory breaker sometimes trips when the machine is powered on, even when only the transformer is attached. I am unsure what the inrush current of the transformer will be, but I assume relatively high. I assume this requires me to have the main isolator for my factory in the business park electrical cabinet changed. Do I have to chat to Jemena to do this? Or do I have to chat to the owner corporation, or by some wonderful magic, neither. The electrical cabinet is quite a long way from my factory, so I'm wondering what the max current is on the cables in between too.Machine states that voltage is 200V, main motor is 44A, full load is 179A. Transformer says it's secondary is 200AWhat would the correct breaker amounts be?I'm unsure of the meaning / relevance of full load in this context. If the main spindle is using 44A at 200V max, say that's 14kW that's not a ton, the coolant pump, motion servos, controller and fans can't consume that much extra power can they?

author: jonpaul
author_rank: Super Contributor
timestamp: July 03, 2024, 05:36:15 am
content: Hello a diagram of photo of the setup will aid, as the post s somewhat confusing.Suggestan elctricians forum in your country,USA the best is Mike Holthttps://forums.mikeholt.com/Found one in AUhttps://www.electriciansforums.net/forums/australian-electrician/usually you get some expert responses.Jon

author: loki42
author_rank: Frequent Contributor
timestamp: July 03, 2024, 08:59:30 am
content: My basic question, without the extras isMachine voltage after transformer of 200V, main motor is 44A, full load on label is 179A. Transformer says it's secondary is 200AWhat would the correct breaker amounts be for the 400V powering the transformer?

author: trobbins
author_rank: Frequent Contributor
timestamp: July 03, 2024, 10:20:33 am
content: Did the factory breaker trip at turn on, or during operation? Does the lathe operate at load with any breaker tripping?I'd anticipate changing the C40 to D40 would not require any change to wiring, and if that allows the step down Tx to be energised without tripping then that is the easiest path to take.

author: jonpaul
author_rank: Super Contributor
timestamp: July 03, 2024, 10:40:13 am
content: Breakers have specs including the magnetic and thermal trip curves vs ambient T and IT product etc.See excellent app notes of IET, ABB, Busman, Square D, Etaon, etc.Jon

author: loki42
author_rank: Frequent Contributor
timestamp: July 03, 2024, 10:51:58 am
content: Quote from: trobbins on July 03, 2024, 10:20:33 amThe street cabinet and factory breakers both trip at start up, when none of the machine is attached to the transformer (or with the machine attached to the transformer) this happens around 1/4 of the time, no difference in frequency if machine is attached or not.Machine Main Breaker: 225A (Japanese voltage) -> Machine Breaker on the Panel: 50A (D50) (AU Voltage) -> Factory Main Isolator on the Panel: 40A (C40) -> Building Main Isolator outside cabinet near street: 40A (C40).I haven't yet operated the lathe, as this happened while it was being commissioned.

author: loki42
author_rank: Frequent Contributor
timestamp: July 03, 2024, 11:30:58 am
content: Quote from: jonpaul on July 03, 2024, 10:40:13 amWhat I'm confused about isn't the curves / etc of the breakers but what the actual demands of the machine will be, specifically the in rush current for the transformer

author: trobbins
author_rank: Frequent Contributor
timestamp: July 03, 2024, 01:46:28 pm
content: Ta. Then yes imho the first issue is transformer inrush. For that you either need to change the C40's to D40's and cross your fingers, or insert some form of beefy softstart resistor/contact timer option, or insert a more complicated soft-start. Then cross your fingers that a 40A breaker is sufficient for any lathe loading.It's a good idea not to keep resetting the cb too many times to test or hope that the breaker stays in, as the cb contact will be stressed more than normal.I had a similar issue with a C40 and a large variac, where the feed cable couldn't easily be ugraded to a C50 or 63 (from a high current busbar board), and the cb was tripping every now and then on start.You could ask your sparky what they can and can't do wrt swapping out cbs.

author: themadhippy
author_rank: Super Contributor
timestamp: July 03, 2024, 02:30:21 pm
content: QuoteNot quite as simples as that,the maximum earth loop impedance for a type D mcb is half that of a type C,uk regs gives a max value of 0.46ohms for a 40A type C whilst a for D type its 0.23 so larger cables maybe required to get the loop impedance to an acceptable level.Quote179A would be my starting figure if i was ask to install a suitable supply for the machine unless the manufacturers said different.

author: loki42
author_rank: Frequent Contributor
timestamp: July 04, 2024, 01:20:10 am
content: My confusion is that the main spindle, by far the largest power consumer is 14kW. That's only 24 amps at 400 V. The big amp numbers are after the transformer, so we need to translate voltages. The coolant and hydraulic pumps are pretty small as is the live tooling spindle. So I'm unsure what needs the rest of the current unless that's to account for inrush.

author: Marco
author_rank: Super Contributor
timestamp: July 04, 2024, 07:22:29 am
content: Isn't a transformer switching relay an option?

author: Poroit
author_rank: Frequent Contributor
timestamp: July 04, 2024, 08:11:37 am
content: Have a chat to Simon at Practical Control Solutions.https://www.practicalcontrol.com.au/power_management.htmlI always found him very knowledgeable when it comes to power issues.

author: loki42
author_rank: Frequent Contributor
timestamp: July 04, 2024, 12:45:24 pm
content: I'm unsure what a transformer switching relay wild be in this context? Some way to slow down inrush?

author: Marco
author_rank: Super Contributor
timestamp: July 04, 2024, 12:54:13 pm
content: https://www.fsm.ag/fileadmin/pdf_Dateien/Trafosanfteinschalter/FSM_Datasheet_TSRD_190410.pdfThey pulse the transformer a few times with thyristors to get magnetization where they want it, then switch in the contactor at the appropriate phase delay.It's the equivalent for inductive loads what a zero cross relay is for capacitive loads, unfortunately it becomes a little more complicated.

author: Geoff-AU
author_rank: Frequent Contributor
timestamp: July 04, 2024, 11:58:08 pm
content: Without the extra pulsing you can still reduce inrush by switching inductive loads at the mains peak voltage. "Peak switching" SSRs exist but are rare, but if you can find one that handles the current you need it might be worth a shot. You could have a delay circuit that switches in a contactor to reduce power dissipation in the SSR once the system is running.

author: jonpaul
author_rank: Super Contributor
timestamp: July 05, 2024, 05:22:17 am
content: use a motor start contactor with current limit series resistorj

author: loki42
author_rank: Frequent Contributor
timestamp: July 07, 2024, 01:38:57 am
content: Is there a way to calculate the breaker required for that transformer if I just went for breakers? Like would a 63 amp D curve be enough? Given just the transformer, I assume there's a way to calculate in rush current?

author: themadhippy
author_rank: Super Contributor
timestamp: July 07, 2024, 01:53:46 am
content: QuoteIf the machine is wanting 179A at 200v, 63A at 400v is still a bit low,100A is more like it.Quoteinrush current = 1.414 x supply voltage /primary winding resistance

author: loki42
author_rank: Frequent Contributor
timestamp: July 07, 2024, 07:26:43 am
content: Some of my confusion is where all the extra power requirement comes from. If the main spindle is only 20 amps that's a whole lot of amps for a coolant pump, controller and servos. Unless they are accounting for inrush somehow.

author: Bafflegab
author_rank: Newbie
timestamp: July 07, 2024, 05:12:31 pm
content: Have you contacted the manufacturer/dealer/rep for the lathe? Most high end manufacturers and dealers are able to tell you what you need to have to power their products...

author: duak
author_rank: Super Contributor
timestamp: July 07, 2024, 05:43:40 pm
content: Madhippy's reply of a current draw on the order of 100 amps is correct. This means at least a 100 amp breaker and power cable to match.I occasionally work with both manual and CNC lathes and mills. Lathe spindles have a large rotating mass (ie. inertia) to start and stop because of the large chuck and workpiece. As a result, the current draw during acceleration stays high until the spindle is up to speed.I get the impression this is a CNC lathe with a Variable Speed spindle drive. If you're stuck with a branch circuit of 40 amps, you might be able to reduce the current by lengthening the acceleration time. On older drives this could be done by varying the configuration DIP switch settings. Newer drives allow acceleration parameters to be changed in the CNC control.BTW, stopping the spindle requires that the rotating energy be dissipated in either a brake, some dump resistors or regenerated back to the power line.More info on the lathe and its spindle drive would be helpful.Cheers,

author: loki42
author_rank: Frequent Contributor
timestamp: July 08, 2024, 01:59:07 pm
content: The lathe is a Nakamura Tome WT 250 mill turn. It's total weight is 8000 kg so there's a little bit of weight to spin in the spindle / chuck.

author: duak
author_rank: Super Contributor
timestamp: July 08, 2024, 08:56:06 pm
content: Loki, thanks for sharing the type of machine. I downloaded version II of the spec blurb from Nakatome and hope it's generally applicable to your unit. Does yours have a Fanuc control and Fanuc axis and spindle drives? I have a small amount of experience with a Fanuc system on a vertical mill. I have much more with Mitsubishi and Mazaks. My experience is that systems of similar vintage have similar designs, capabilities and characteristics. For the past 20+ years, the drive systems generally have one AC to DC link converter module that provides all the DC to the various axis and spindle drives. It also dumps or regenerates excess energy from deceleration.Oddly enough, I recently helped a friend connect and operationalize a Mazak Mill-turn about the same size as your Nakamura. It is a 400 V unit with a 208 to 400 V step up transformer. It replaced a simple vertical mill that had a 60 A branch line for power. We know that is undersized, but until we get the software sorted out it will do fine. The 100 A breaker on the transformer occasionally trips with neither spindle turning but the 60 A breaker in the panel doesn't. Go figure.In your situation I agree that because there are a number of smaller spindles rather than one big one and if you're not maxing them out at the same time, the current draw should be lower. In the end, I think you'll need more current, but let that pass for now.If I understand correctly, closing the branch line breaker to the transformer with the Mill-turn off can cause the breaker to trip? Transformers indeed have an initial surge current that can trip a breaker. A slower responding breaker should help, but I'm not up on Aus's code and what is permissible and what parts are available. In North America, branch lines have a calculated load amp limit rating of 80% of the cable ampacity. For hardwired motor branch circuits we are allowed to use a breaker with the next higher ampacity if needed. eg., a 14 gauge, 15 A branch line is protected by a 15 A breaker but is not to be loaded more than 12 A . In this case if the breaker trips, it is permissible to use 20 A. I don't know if breaker uprating is permissible in Aus and should be checked out.Some type of electronic motor soft starter might work with a transformer but they're not cheap and I don't know if they would work with CNC motor drives as a load.There are motor starters that introduce a series resistance in each phase line to limit current. Expensive new but you might luck into a used one. There's no rocket science to building one. One would need three heating elements of a few ohms at a few hundred watts each for series resistance plus a timer and a contactor to bypass them after a second or so. I don't know about any regulatory requirements such as permits or inspections.Edit: are any of the breakers magnetic? They often respond to surge currents that thermal breakers ignore.Edit: Is the transformer supplied by Nakamura and/or part of the Mill-turn or something supplied separately? I ask because at one site I looked at, a delta-wye step down transformer was used in reverse to step up the supply voltage. The electrician had wired the neutral of the wye (now the primary) to system neutral as one does. The problem is that any system voltage imbalance leads to large circulating currents in the transformer. This leads to heat and this transformer was running hot even when unloaded.. Eventually a fuse opened and I was asked to look at it. I found the neutral current, disconnected the undesired connection and it worked fine for years afterward. BTW, a floating secondary is considered unacceptable because the phases may have higher than expected voltages to ground. This is no longer a problem as it was decommissioned recently.Hope this is of some help,Cheers from Canada, eh?

author: loki42
author_rank: Frequent Contributor
timestamp: July 10, 2024, 10:30:48 am
content: Quote from: duak on July 08, 2024, 08:56:06 pmThe drives and controllers are from Fanuc. There is 2 ac to dc units, one for each spindle / axis set.The transformer is from Nakamura Tome.I have no idea if the breakers are magnetic... I didn't even know they came in different types!I've got a photo from the previous owner and they were running an 80 amp c curve breaker with it.I got the sparky in yesterday and the main input can be upgraded. The front Junction has 35mm2 cables, and 16mm2 to the machine so that should be enough for 100amp main breaker for the factory and then an 80amp breaker for the machine. I'm not sure if a smaller breaker with a different curve would work but they are the same price so I might as well you go for the bigger one.Bigger breakers is way cheaper than any of the complicated soft start stuff.

author: duak
author_rank: Super Contributor
timestamp: July 11, 2024, 02:28:55 am
content: Loki, the correct cable and breakers are definitely the right solution. It's a bonus that they are not more expensive than bodges. Hopefully, there are no gotchas.Oh, and if you don't know for sure, confirm that all backup batteries are in good shape. The one Fanuc CNC I worked on runs its axis encoder batteries down quickly - on the order of a year. The Mazak Mill-turn I mentioned above came with two dead batteries. That was fun.All the best,

author: .RC.
author_rank: Frequent Contributor
timestamp: July 11, 2024, 03:21:54 am
content: If it is industrial, shouldn't you have something like 80 to 120 amps per phase running into the building?

author: loki42
author_rank: Frequent Contributor
timestamp: July 11, 2024, 12:47:51 pm
content: All the factories in this industrial park have 40 amp breakers for some reasons, and the cables need to be upgrade in the electrical box at the front of the park. Luckily the ones under the ground are decent. Australian building, If they can make it cheaper they will.