# Calculate contactor capacity for AC22

#### meowsoft

Joined Feb 27, 2021
549
Is there any way to convert AC1 nor AC3 capacity in a contactor for AC22 load ?
Example :
LC1D09M7, AC1 : 25a, AC3 : 9A, how can I calculate for AC22 ?

AC-1, Non-inductive or slightly inductive loads, example: resistive furnaces, heaters.
AC-3, Squirrel-cage motors: starting, switches off motors during running time.

Joined Jul 18, 2013
25,211
What are the particular application details?

#### meowsoft

Joined Feb 27, 2021
549
What are the particular application details?
Its for distribution change over switch, about 80% is resistive (mostly server equipments, running for 24/7), another is moderately and highly inductive (water pump, bench drill, air conditioner, ...)

#### meowsoft

Joined Feb 27, 2021
549
Do you think I can use load percentage ?
Example : LC1D80AM7, AC1 80a, AC3 66a
AC1, 80% x 80 = 64a
AC3, 20% x 66 = 13.2a (Rounded down to 13a)

Joined Jul 18, 2013
25,211
You may be OK using a suitable current/HP rated NEMA contactor, these are truly General Purpose contactors and cover a wide spectrum.

#### MisterBill2

Joined Jan 23, 2018
11,880
Using a contactor for a distribution changeover switch is not efficient because the coil in a contactot draws a fair amount of current. And how often would the source of power for a distribution panel be changed?? A motor driven switch wouold be a much better choice.

Joined Jul 18, 2013
25,211
I disagree, DC contactor coils are very efficient.

#### MisterBill2

Joined Jan 23, 2018
11,880
I disagree, DC contactor coils are very efficient.
I did not say that the contactor coil is not efficient, but that it draws a fair amount of current, and drawing a constant current is a lot less efficient than only drawing current to operate a switch mechanism.
The TS is talking aboutcontactors feeding distribution panels to select alternate power sources. So that will be at least a 40 amp comtactor, more likely a 60 or 100 amp rated one. Not small. And this would be continuous operation.
And unless the establishment has DC mains power, the control would also be AC, unless a separate power supply is added.

One more thing, referencing the loads as AC1, AC3, and AC22tends to be unclear, as the description was not provided. Later there is a bit of a description, sort of.
This is another case of not providing nearly enough information as to the background for the question. That will lead to a bunch of guesses not really related to the answer needed.

Last edited:

Joined Jan 15, 2015
6,585
Using a contactor for a distribution changeover switch is not efficient because the coil in a contactot draws a fair amount of current. And how often would the source of power for a distribution panel be changed?? A motor driven switch wouold be a much better choice.
The image below is a 100 Amp 240 Volt split phase AC transfer switch.

Operation simply involves two independent contactor switches activated by two 12 VDC solenoids. The contactors are mechanically and electrically ganged to prevent both from supplying the load simultaneously. Electrically each contactor has a microswitch. Each solenoid is simply pulsed with 12 VDC and pulse duration is about 2 seconds. 200 Amp and greater work the same way. The coils require less than a 1.0 Amp pulse. This is how most ATS (Automatic Transfer Switch) systems work. In this example the contactors feed a 100 Amp distribution panel. There is no need for a motor driven switch.

Ron

#### MisterBill2

Joined Jan 23, 2018
11,880
OK, a solenoid is close enough to a motor for this application. Thanks for showing the TS that there are other ways than contactors.

#### meowsoft

Joined Feb 27, 2021
549
The image below is a 100 Amp 240 Volt split phase AC transfer switch.

View attachment 265934

Operation simply involves two independent contactor switches activated by two 12 VDC solenoids. The contactors are mechanically and electrically ganged to prevent both from supplying the load simultaneously. Electrically each contactor has a microswitch. Each solenoid is simply pulsed with 12 VDC and pulse duration is about 2 seconds. 200 Amp and greater work the same way. The coils require less than a 1.0 Amp pulse. This is how most ATS (Automatic Transfer Switch) systems work. In this example the contactors feed a 100 Amp distribution panel. There is no need for a motor driven switch.

Ron
It is same with contactor pushed with solenoid ?, do you have some 3D printed schemes for this ?, maybe I can mount solenoid that pushed contactor mechanically like LADN11 mounted into LC1D contactor series...

#### meowsoft

Joined Feb 27, 2021
549
The image below is a 100 Amp 240 Volt split phase AC transfer switch.

View attachment 265934

Operation simply involves two independent contactor switches activated by two 12 VDC solenoids. The contactors are mechanically and electrically ganged to prevent both from supplying the load simultaneously. Electrically each contactor has a microswitch. Each solenoid is simply pulsed with 12 VDC and pulse duration is about 2 seconds. 200 Amp and greater work the same way. The coils require less than a 1.0 Amp pulse. This is how most ATS (Automatic Transfer Switch) systems work. In this example the contactors feed a 100 Amp distribution panel. There is no need for a motor driven switch.

Ron
Good idea...

#### meowsoft

Joined Feb 27, 2021
549
Is anyone have 3D printer schematic for MCB recloser ?, I think thats good idea too... I have local produced third party MCB recloser that can works for general MCB like Schneider, ABB, Hager, Siemens, etc, but thats not very reliable... thats can be used for changeover switches too...

#### meowsoft

Joined Feb 27, 2021
549
Is anyone have 3D printer schematic for MCB recloser ?, I think thats good idea too... I have local produced third party MCB recloser that can works for general MCB like Schneider, ABB, Hager, Siemens, etc, but thats not very reliable... thats can be used for changeover switches too...
Like this...

But more reliable, use 3D printed actuator to change MCB actuator position...

Joined Jan 15, 2015
6,585
Sorry, I do not have any3D image. The picture I posted is an old ATS (Automatic Transfer Switch) from an old 13 KW backup generator from my house. I have used much larger units in commercial applications. Where I am there are code requirements we have to meet both residential and commercial applications. The transfer switch chooses between to AC power sources and feeds a circuit breaker panel. There is likely a dozen manufacturers making transfer switches so they are easier bought than made.

Ron

#### meowsoft

Joined Feb 27, 2021
549
Sorry, I do not have any3D image. The picture I posted is an old ATS (Automatic Transfer Switch) from an old 13 KW backup generator from my house. I have used much larger units in commercial applications. Where I am there are code requirements we have to meet both residential and commercial applications. The transfer switch chooses between to AC power sources and feeds a circuit breaker panel. There is likely a dozen manufacturers making transfer switches so they are easier bought than made.

Ron
Yes, but not in CN...
Anyway... Its very good idea...
Whats amps they normally draw when pushing contactor ?

#### meowsoft

Joined Feb 27, 2021
549
Yes, but not in CN...
Anyway... Its very good idea...
Whats amps they normally draw when pushing contactor ?
Do you think its good to use stepper motor like this video ?, but to push contactor mechanically not MCB, and using PLC, I think arduino is not adequate

Joined Jul 18, 2013
25,211
Not a good idea for a contactor IMO, it should be sealed in as quickly as possible.
With the breaker it has flip over mechanism internally.

Joined Jan 15, 2015
6,585
Yes, but not in CN...
Anyway... Its very good idea...
Whats amps they normally draw when pushing contactor ?
Less than am amp for less than i second. The one I used a picture of the coils draw about 750 mA at 12 VDC using a two second pulse. The actual contactors are rated for switching a 240 VAC 100 Amp load.

Ron

#### MisterBill2

Joined Jan 23, 2018
11,880
There is a HUGE difference between a contactor and a powered transfer switch, which is that the coil in a contactor is constantly powered to hold the contacts closed, while with a transfer switch the coil is only powered long enough to make the change and latch the contacts in position. So the coil is powered for just a few seconds, instead of for months. THAT is the reason that I stated that using a contactor is not efficient.
AND, printing all of the parts for a transfer switch is not a wise choice because of the many different materials used and the close tolerances, and the high forces involved.
In addition, controlling the source of mains power is not where I want a beginner in making things involved.