Understanding Contactor, VFD, Control Box Relationships

[curriergroh]

I need some help understanding where a contactor goes and how it interacts with various other components.

Here are the parts of my setup:

The spindle (kelling 2.2kw 3hp) is connected to a VFD (hitachi x200, 3hp), the VFD is powered by 3 phase 120/208.
The control box is powered by 120V single phase and has PMDX-122 breakout board and a PMDX-106 spindle control board.
There is also 5V powering the PMDX-122 and PMDX-106.
There is also a 12V supply in the box but it is currently just being used for cooling fans.

I have been told not to rely on the software estop of Mach3 to power down the spindle, and I agree, but to do it right I need a contactor that will take an estop signal and kill power to the spindle.

I don't understand where the contactor goes.
I don't understand if it is cutting power to the VFD or cutting power to a relay which cuts power to the spindle control board etc.
I think that it would go in the control box, but what is it connected to? What type of power/circuit is it wired in to?

I try to read as much as possible before asking questions, but these contactors and relays still leave me foggy after many hours.

[Al_The_Man]

The contactor is used to provide the 3 phase input supply power to the VFD and the coil is normally controlled by the E-Stop circuit.
Do not place the contactor in the VFD 3 ph output.
The E-Stop should be a hard wired circuit with all the functions you need to initiate an E-Stop should be in the series string.
I prefer to use a low voltage circuit with the output being a small control relay.
A contact on this relay would cut off 120v or other supplies providing power to contactor coils etc that are controlling power to VFD, drives etc.
This avoids running 120v power in the E-Stop string.
Al.

[hub]

Al is correct. I'm trying to put it in simple terms:
- The VFD input is not necessary 3 phase, it might be 1 phase. But you said your Hitachi is 3 phase, is than input and/or output? Anyway it doesn't matter, except for the type of contactor.
- Software should never be relied on for e-stop.
- The contactor should be between mains and vfd (vfd input).

[curriergroh]

I hope you guys are feeling patient.
The VFD is powered by 3phase 120/208. I am in an industrial building.
The control box is powered by 120v single phase.
I don't have estops yet so I don't know how they are powered.

Do I need more than one contactor becasue I have different power sources?
For example a contactor that goes in front of the VFD to stop power to the spindle and another conactor that stops power to the drivers/motors?

The X200 says it has an estop circuit. Does that change anything?

[Al_The_Man]

By rights you need a means of disconnecting the VFD and AC power to the drives P.S.
For the VFD this will be a 3 phase contactor in the 3ph 208.
If you are building the machine you can power the E-Stop which ever way you wish.
For the 120v single phase power to the drives or any other piece of equipment you wish to E-stop, then they would also need either a large relay or contactor.
You may find it cheaper to go with contactors as they can be had on ebay fairly cheaply.
If you do not have much more than VFD and drives you can combine the control on one contactor, they can be obtained in 4 pole, so 3 would be the 208 3ph and the the fourth would be the 120vac to the drives, the neutral does not need to be switched.
For simultaneous E-stop of items such as Coolant or Vacuum etc that are often controlled by M code, an auxilliary contact on the main contactor could control power to the relay coils for these devices.
I will see if I can pull up an example from a past project.
It is recommended that suitable fusing be used before any contactor or relay for each device.
Al.

[Al_The_Man]

This is a couple of DXF's you may be able to get some idea or modify to what you need.
It wasn't a Mach system, but some E-stop practices are the same.
I had to zip them due to size, they are actually RAR files so they may have to be renamed, the forum only allows ZIP at the moment.
Al.

[curriergroh]

Thanks for uploading those. I was able to extract without changing the extension.

I'm starting to understand how this is going to work, albeit slowly and not fully yet.

I would like to find a source for a contactor that will fit my situation.

• If I want to switch the vfd/spindle which has input of 3 phase (4 wire) then I would need 3 poles for the 3 hot lines.

• If I also want to switch the 120v which is the source power for driver/motor's DC power supply then I need 1 additional pole for the positive line.

• Then if I also want to switch the water pump I could use an Aux contactor.

How do aux connections work on contactors?
The Coil voltage has to match the control circuit voltage, right? So if the control circuit is 24v DC then I would need a 24v dc contactor coil.

What is the difference between a 3pole contactor with 1 aux and a 4 pole contactor?

[Al_The_Man]

4 pole contactors have 4 switching contacts rated at the current capacity of the contactor, auxiliary contacts come in N.O. or N.C. type and just clip into the Contactor and are actuated by the contactor armature in the same fashion as the main contacts, just that they are usually for low current devices or control circuits.
I usually go for Telemecanique brand, they are often plentiful on ebay, as well as screw mount, they are also DIN rail mount and come with various clip on options.
Al.

[curriergroh]

I spent some time with a circuit diagram from a friend and this is all starting to make sense.
Based on your feedback and what I have learned. I decided to dismantle the control box to start fresh instead of forcing new parts to work with the old parts. I mentioned in the original post that I needed to disconnect and switch 3 phase and 120 single. That no longer seems appropriate.

My strategy now is to just bring 3 phase into the control box, through a disconnect door switch and then through a contactor. The e-stop circuit will have 120v from L1 and N coming off the mains before the contactor. After the contactor I will be able to distribute 3 phase to the VFD and 120v to the power supply for the drivers.

I also drew up a circuit based on a friends MechMate where the momentary ON button goes through the contactor coil and one of the poles so that after pressing it the coil stays energized. But I am unsure if that circuit should use one of the poles or an aux contact. I am also not sure if the N of the 3 phase needs to be switched or just L1, L2, and L3.

So can you help me figure out what contactor I need for this situation? I don't know which is more appropriate a 3 pole with an aux, or a 4 pole.

Can you also educate me on the sizing of the disconnect and the contactor?
What should the amp rating be? Should the disconnect and contactor be rated the same?
I have a Keling 6520, 65V DC and 20A power supply and a Hitachi x200 3hp that outputs 10A.
I am doubting that it is as simple as adding 20A and 10A because of increased startup loads.

[Al_The_Man]

The E-Stop method you mention is the one shown in the prints I posted, you can use one of the 4 poles if it is not being used, but the normal way is to use a 3 pole with an aux N.O. contact.
The neutral is never switched, just the live conductor.
IIRC the current code for sizing a disconnect and any main fusing is 2.5x the current rating of the total load.
The contactor in your case can be at the rated load it is supplying.
Al.

[curriergroh]

Al, THANK YOU for the help.

Can you explain these comments made by HuFlungDung in a post from 2007 that you participated in?
I have a feeling he is saying that the 24V DC supply provided by the Hitachi X200 should be used for the estop circuit. But if that is the case why am I putting a contactor where I'm not supposed to. I'm sure I'm just not understanding.

And in case anyone else is reading. In another thread Al posted a link to this website: All About Circuits : Free Electric Circuits Textbooks It has been very helpful for me.

So here are the comments that I am asking about.

You'll want to use the VFD to create the spindle motor control system.

Estop and on, off, reverse must be handled within the VFD as you must not break the main power between the motor and the VFD output.

[Al_The_Man]

The normal on/off fwd/rev should be done by the VFD low level inputs.
For E-stop, you should use a contactor on the input side of the VFD, a contactor should not be used between VFD and motor unless there are extenuating circumstances and if so, special steps have to be taken to avoid dropping or picking up the contactor when the VFD is outputting power to the motor, not applicable in your case.
It is also recommended that if the contactor is dropped in an E-Stop, the input run should also be dropped out, normally this is done by the controller anyway where the controller is advised that an E-Stop has taken place.
Another link.
http://www.hs-compliance.com/uploade...NCY%20STOP.pdf
Al.