[oxford]

Thanks Pat.

I am looking to run one VFD and multiple servo drives.

I see a lot of enclosures using terminal blocks. Are terminal blocks just used to keep the wiring neat?

[wildwestpat]

Hi Oxford

Yes use terminal strips to keep the wiring neat and avoid the possibility of short circuits in the wiring. However keep all wires as hort as possible and of course stick to an earthing policy that keeps induced noise to a minimum.

If you use the DIN rail mounting contactors, signal relays. RCB, fuses etc there are also DIN rail mounted terminal strips (barrier type).

My preefrence is to use barrier strip terminals with crimp on eye tag terminals as this helps avoid accidental shorts.

Just a point about the difference between the emergency stop - got my hand in the cutter - from the E-stop used in CNC. Arrange for the servos to have their drive status set to off prior to cutting the power to the servo drives. This is important to protect the electronics and would also with a suitable CNC program enable the machine to be restarted and the job saved. I like to think of the E-stop as - the cutting tool need changing as it is not cutting well or the swarf is out of control - and the action is to halt the machine quickly in a way that will permit recovery of the machining operation. The Emergency Stop is then reserved for the situations where you are being hurt or see some one else being hurt and it is necessary to stop the machine as soon as possible regardless of the damage to the work piece.

The choice of RCD or fuse needs to take into account any inrush current of the filter associated with the VFD. Some of the filters can due to their high inrush current rrip the RCD during switch on and you may need to use a fuse or use an RCD designed to permit the high inrush but still trip on sustained overload. The RCDs are normally used for large flourescent lighting loads and cost is about the same as the normal domestic RCD and are often fitted where computers or microwave ovens cause nuisance tripping when turned on from rest.

Good luck and stay safe - regards - Pat

[oxford]

When wiring power to multiple drives, can I run some parallel bus lines for ground, live, and neutral and then just twist the wires coming off of them? (As shown in drawing)

Or do I need to twist the bus lines as well?

Thanks

[oxford]

The drawing I meant to attach earlier :P

[Al_The_Man]

Normally there would be separate protection for each drive.
If a disconnect contactor is not supplied for each VFD then there could be one main contactor with the output side of the contactor going to individual fuse blocks or NFB (Non Fused Breaker) for each VFD.
The neutral would normally be from a distribution block with a conductor to each drive.
Likewise the Ground for each.
The three phase motor conductors are the ones that are recommended to be tightly twisted.
The contactor would normally be picked up by the E-Stop circuit.
Al.

[wildwestpat]

Hi Oxford

The neatest way of configuring the power input wiring to your multiple VFDs is to create a common bus bar (Terminal strip) for each phase + neutral + earth. You may or may not need the neutral. The type of wire needs to be suitable for the intended purpose both in terms of current carrying capacity and insulation and mechanical protection. The leads from the VFD to the motor should be both short and screened as these carry high frequency currents and can create a lot of radio interference. Suggest you use flexible screened wire or metal conduit to carry these wires. The appropriate wire would be SY multicore cable. This cable is flexible and is available in current ratings as well as multicore and termination is made using special glands available in both 20 and 25 mm conduit sizes. (Three, four, five and seven core are commonly available.) The SY cable could be used to wire the power input side of each VFD back to the power distribution box that contains the contactor/s and the supply fuse or RCD and isolator following the local regulations governing both the electricity supply and the health and safety regulations.

The easiest way of achieving the power distribution is to use a three phase distribution box (often known as a TP+N with isolator - this will provide a three phase isolator switch and the necessary bus bars and if the DIN rail type is procured there will be one or more rails to which the appropriate current breakers (MCBs) or fuse carriers can be fitted along with the DIN mount four pole contactor.

Suggest you procure a catalogue from your local electricians supply house. The three phase distribution boards are arround £100 in the UK for the box and isolator with DIN rail. A four pole contactor is arround £30 to £50 depending on current capacity - don't forget the VFD looks like a capacitive load and it is the in-rush current that is important not the running current. If you are using over current breakers (MCBs) then these need to also be rated for the in-rush current and I would suggest type 'C' not the more usual usual type 'B' which has a lower in rush capability.

The use of twisted wires can cause problems as the insulation can easily flow particularly if the wires are not de rated for such use. Normally the wire has to be of higher gauge if run in close proximity to other current carrying conductors - hence my recomendation to use type 'SY' cable.

Hope this helps you achieve a neat and safe installation - regards Pat.

[Al_The_Man]

My only concern with bussing to each VFD without protection for each VFD, is it contravenes the code in N.A. anyway, especially as we do not know the individual sizes of each VFD.
I personally protect each with a appropriate fusing.
Also if a 3 phase contactor is used and enabled by the E-stop circuit, a pole of the contactor can be assigned to each VFD, usually up to 4 for some contactors.
Al.

[wildwestpat]

Hi Oxford

To give you some ideas here are some links to commercial TP +N distribution boxes

http://www.hager.co.uk/files/downloa...t_brochure.pdf

http://www.electrium.co.uk/WylexThreePhase.pdf

http://www.sycable.co.uk/

You will find that there are local suppliers of similar products and I am only suggesting that you view these links to give you an idea of what is available.

Since the public mains supply company will have provided an incomming feed meter and company fuse the maximum sustainable current is determined by the blow characteristics of the electricity supply companies fuse. The recommendation is that the idividual VFDs should have their own thee pole MCB or fuses - unfortunately the contactor will if swithed on to a faulty VFD or wiring short will suffer some contact damage as the MCB or fuse will take some finite time to trip / blow. As far as I am aware the MCBs provide adequate protection even when type 'C' or 'D' are used and can safely disconnect arround 6,000 amps fault current.

regards

Pat

[oxford]

Thanks for the input.

I have been looking at enclosures to avoid reinventing the wheel. Some of the parts I can't identify yet and wanted to make sure I would not miss out on something important.

I want to say the parts I can't identify are terminal strips and fuses.

[Al_The_Man]

My guess, the top and bottom ? is a terminal strip, with possible entry allowed from the opposite side for external entry wiring.
The second down "Fuse?" a Disconnect?
The next "fuse?" down is possibly a Safety Relay, i.e. special form of E-Stop Relay (could also be a timer).
The one above the disconnect appears to be a Contactor.
A closer pic could confirm these guesses.
Al.

[Al_The_Man]

Update, re your query post on Panduct, here is an alternative where Panduct is not practical to use.
They are tie wrap mounts.
There is also something called Spiralwrap, this is used around cables that go from door to enclosure, to aloow the wiring to flex when the door is opened.
http://www.cabletiesandmore.ca/SpiralWrap.php
Also the components in your picture appear to be mounted on DIN rail, almost any electrical component now comes with DIN rail mount ability, even transformers.
The clip on to DIN terminals are made by Allen-Bradley, Weidmuller, Phoenix-Contact, Entrelec, for a few.
Al.