Hello Everyone,

I'm currently working on a project where I aim to remotely control a 3-phase 22kW water pump motor using an Arduino microcontroller. To achieve this, I'm considering using relays as ON/OFF switches between the Arduino and a contactor that will ultimately control the motor.

However, I'm seeking some expert advice on whether this setup is feasible and, if so, what type of relay would be suitable for this application. Specifically, I'm interested in knowing:

1. Can I use relays to act as ON/OFF switches between an Arduino and a contactor that controls a 3-phase 22kW water pump motor?

2. If yes, what type of relay should I use for this purpose? Are there any specific specifications or features I should look for in the relay to ensure compatibility and safety?

3. If using relays is not advisable for this application, what alternative solutions or components would you recommend for achieving remote control of the water pump motor with an Arduino?

I would greatly appreciate any insights, recommendations, or experiences you can share on this topic. Your expertise would be invaluable in helping me move forward with my project.

Thank you very much for your time and assistance.

Best regards,
Aravindan

 

I aim to remotely control a 3-phase 22kW water pump motor

How remote is "remote".

Yes you can use a high current mechanical contactor (high-current relay).
(What is the pump supply voltage as the determines the current rating?).

You likely need another relay to power the coil of the contactor since it likely requires a fair amount of current.
An SSR (solid-state relay), could be directly controlled by the Arduino for this purpose

Is this homework?

 

OK, the project certainly makes sense, and certainly a relay will be required to switch power to the three phase contactor. That is the only sensible scheme that is not terribly complex.
I recommend an adequately rated solid state relay to control the contactor, which could be a CRYDOM brand device or an equivalent. The SSR that uses a 5 volt signal will be a close match to the arduino. The challenging portion will be the mechanical arrangement of the power switching contactor for motor starting.

 

If it is as simple as has been presented, just a pump and a contactor, then I agree with the suggestion of a SSR. But if there is a preexisting control circuit with pushbuttons, other relays, etc.; if a NC contact is required for any reason then an electromechanical relay may be a better fit. To interface an electromechanical relay to arduino there are many options, but I won't waste time discussing them unless the application demands an electromechanical relay.

 

I think we need to know why the TS referred to Relays (plural).
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I think we need to know why the TS referred to Relays (plural).
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I assumed that was a typographic error!
If the TS is intending to use one contactor per phase to switch on a three-phase motor then it is very unlikely to be a satisfactory effort. It is not likely that the three would function "in perfect unity." So there would be a very large starting current surge.

 

I assumed that was a typographic error!
If the TS is intending to use one contactor per phase to switch on a three-phase motor then it is very unlikely to be a satisfactory effort. It is not likely that the three would function "in perfect unity." So there would be a very large starting current surge.

I interpreted differently, that this might be an existing pump control panel with existing controls. It would be typical of such a panel to have at least a latching start/stop pushbutton circuit and depending on function maybe also incorporate level switches for automatically turning on/off the pump. If that's case, a NO relay contact in parallel with the start button, and a NC relay contact in series with the stop button, is how I have interfaced such panels for remote control in the past, and may be what TS intends. Multiple contactors were never mentioned, only multiple relays.

 

Once again we are provided with less than the complete information about the system we are asked to help with. Certainly an interlocking relay system will need a second relay for the stop function, in addition to a whole different software scheme.
Another case of not providing all the information "because we do not need to know that part."

 

Going by the TS's name, it is presumed that he is located in India.

The 22 kW motor would be rated 3 x 415 V ~ 50 Hz, with a full load current of 39 A.

The starting current would be 234 A (6 times the full load current).

Star-delta starting would be required to limit the starting current to less than 3 times the full load current.

Here's the power circuit schematic courtesy theengineeringmindset.com.



Three relays, driven by three Arduino GPIO ports, would be required to drive the common main contactor K1, the star contactor K3 and the delta contactor K2.

The relay contact rating would be decided by the contactor coil current at switch-on.

The contactors K2 and K3 would need to be interlocked to prevent mains short-circuit in the event of both of them being simultaneously switched on inadvertently.

Nandu.

 

I'm currently working on a project where I aim to remotely control a 3-phase 22kW water pump motor using an Arduino microcontroller. To achieve this, I'm considering using relays as ON/OFF switches between the Arduino and a contactor that will ultimately control the motor.

Contactors are rated in HP, and there are many suitable makes to select from, also remember it is usual to use O/L's on the output of the contactor, They have status contacts that can be used to advise the Arduino of this. as well as the normal N/C contact in the contactor coil circuit in order to hold it off until reset.

 

I would recommend a contactor with an 230V AC coil. Switch the coil using a triac and an opto triac.

(Another member who is contributing to this thread will recommend a contactor with a DC coil, because it has a longer operating life. However, it is not so simple to drive, needing a reasonable amount of current at 24V DC)

 

REALLY, EITHER A SOFT-STARTER or a variable speed drive will be a much better choice, and much more reliable that a Y-Delta switching starter. First, those starters are subject to destruction from input chattering if the supply voltage sages excessively during a start. Also, they are a bit obsolete, at least that was the case 30 years ago.
Besides that, a suitable VS drive or soft starter will cost less and be quite a bit smaller. Plus it will be much more reliable.

 

(Another member who is contributing to this thread will recommend a contactor with a DC coil, because it has a longer operating life. However, it is not so simple to drive, needing a reasonable amount of current at 24V DC)

But has a lower operating current, lower (no) inrush. much longer life.
Over the years, I have worked on, and installed remote operating stations for the Municipal water supply suppliers etc.
All have a trouble free record.

 

Hello Everyone,

I'm currently working on a project where I aim to remotely control a 3-phase 22kW water pump motor using an Arduino microcontroller. To achieve this, I'm considering using relays as ON/OFF switches between the Arduino and a contactor that will ultimately control the motor.

However, I'm seeking some expert advice on whether this setup is feasible and, if so, what type of relay would be suitable for this application. Specifically, I'm interested in knowing:

1. Can I use relays to act as ON/OFF switches between an Arduino and a contactor that controls a 3-phase 22kW water pump motor?

2. If yes, what type of relay should I use for this purpose? Are there any specific specifications or features I should look for in the relay to ensure compatibility and safety?

3. If using relays is not advisable for this application, what alternative solutions or components would you recommend for achieving remote control of the water pump motor with an Arduino?

I would greatly appreciate any insights, recommendations, or experiences you can share on this topic. Your expertise would be invaluable in helping me move forward with my project.

Thank you very much for your time and assistance.

Best regards,
Aravindan

My suggestion would be a soft starter of some description and used the arduino to drive that through a small control relay. The soft start will give the pump a better life and control the motor in terms of overloads etc most are 24 volt control circuits and have a 24 volt supply sufficient for their control. L:ess stress driving from an arduino through a small control relay and less stress ont the pump as it is started in a controlled manner and the current is limited at start up.

 

While it certainly is possible for a motor starter contactor to wear out, I have never come across that in a piece of adequately designed industrial equipment during my career. So the quest for a more expensive DCpowered contactor that needs a DC supply is not warranted, Instaead, use a solid state relay with an adequate current and voltage rating, such as "CRYDOM" brand SSR devices.

 

While it certainly is possible for a motor starter contactor to wear out, I have never come across that in a piece of adequately designed industrial equipment during my career. So the quest for a more expensive DCpowered contactor that needs a DC supply is not warranted, Instaead, use a solid state relay with an adequate current and voltage rating, such as "CRYDOM" brand SSR devices.

Hello there,

It is interesting that you have experience in this very area.
What I was wondering is if with these huge pumps do they normally incorporate any mechanism to handle any inductive kick back from the pump motor? I could only imagine that when a relay is opened up connected to an inductance that has 40 amps flowing through it just prior to opening, that the 40 amps will be desperately looking for somewhere to go and that would make a good welder if just for a few seconds. Almost sounds like a Frankenstein arc.
Or is it that they rely on some natural operation of an SSR to handle that (using an SSR instead of a contactor).

 

The contacts and operation mechanism leave the connection conducting thru the momentary arc so that the power from the collapsing magnetic field is returned to the power system. THAT is why there are "power glitches" in the wires connected to supply larger motors. That is also why it is not wise to power one's arduino right off of the feed to the motor starter.

 

My reference was to contactor coils, not the contactor itself.
I prefer to use DC coils where ever possible, this ensures many more years of trouble free operation, over the AC operated device.
This practice is much more prevalent in Europe, over N.A.
See post #32 https://forum.allaboutcircuits.com/...urrent-calculation.198203/page-2#post-1876897

 

While it certainly is possible for a motor starter contactor to wear out, I have never come across that in a piece of adequately designed industrial equipment during my career.

I am not sure what you are saying. You've never come across a worn out contactor? Or every time you have, you deemed it an inadequately designed system? Either way I take it your point is that contactor failure is rare. In my experience it is quite regular and in my view contactor failure is guaranteed, on a long enough time scale. If a system is designed and operated such that the lifespan of the contactor exceeds the lifespan of the equipment itself then maybe that is what you mean by "adequately designed" but achieving such a feat in most circumstances would require grossly over-specifying components to the point that the initial cost is more than anyone would pay. I think it is better to use the appropriately rated contactor and consider its internals to be the wear items that they are actually intended to be. This is why you can buy rebuild kits for most contactors. New contacts, new springs, new coils, new snubbers, (for starters/overloads, new heaters) most of these are available for most contactors, and if they are not then you should probably choose a different contactor unless it is cheap enough to justify replacement of the whole contactor.

The lifespan of contactors depends on how often they are switched, the type of load, the magnitude of the load relative to the rating, et. al. They have moving parts, internal arcing, they generate heat, etc. I regularly encounter contactors which have open or welded contacts due to pitting from arcing. Contact springs can weaken or break over time, leading to this, and also it can happen just from the natural arcing which happens every time the load is switched. The moving armature inside a contactor typically slides back and forth inside a plastic or composite housing, each time rubbing off tiny amounts of material. This internally created "dust" and/or dust from surrounding atmosphere eventually (over a span of years usually) causes the armature to get "sticky" or sluggish or not come together fully. This air gap, with an AC coil, will result in the coil melting. With DC the coil doesn't melt (and for this reason I also prefer DC devices like @MaxHeadRoom ) but still the contacts don't close fully and are quickly destroyed.

I do prefer to use SSRs when possible to avoid the disadvantages of contactors but when contactors are needed, they should be well understood and their inevitable failure should not be automatically assumed to be a failure of whoever designed the system.

 

. You've never come across a worn out contactor?

Right! One example I came across, but a little rare, was an AC version that had one of the shading rings worn through, result: Buzzing like H..L.