Hi,

I want to switch ON and OFF a 0.5 HP 230VAC motor (used for pumping water) with a relay module as shown in the image attached.

I plan to use a 9V battery to do so. The relay reads 'JQC-3FF-S-Z' and '10A 250VAC'. The motor's current rating is 3A. The module has other components apart from the relay. I'm assuming they prevent issues like back emf and arcing during switching.

Is it safe to use the module? If not, what do you suggest?

Thanks in advance.

 

That is a 5v dc relay and it appears to be a small bridge rectifier and indicator LED etc.
It has two levels for operating power by the look of it, you would have to refer to the sheet that came with it!
Max.

 

I plan to use a 9V battery to do so.

A standard mechanical relay, such as that module appears to have, will likely take too much current for reasonable battery life.
Better to use a solid-state relay (SSR).
They require only a few mA of control current at a low voltage (usually 3V minimum) to operate.
Three alkaline D cells should operate such a relay for several hundred hours.

 

Also a 9v battery to control a 240vac pump is rather an odd combination, if 240vac is present why not use a small step down unit to control the relay?
Max.

 

Why not just use a regular switch or use line level voltage rated relay and remote switch to control things?

 

Hey Max, crutschow and tcmtech!

Thanks for your responses.

The relay module shown above did not come with a sheet unfortunately. I am unable to find info about it online as well.

I am looking for the lowest cost (and safe!) way of switching 230VAC motor circuit. SSRs, alkaline D cells, step down transformer etc. would drive up the product cost i guess. However, safety and long life are also important considerations.

 

Why not just use a regular switch

There are two type of switches that I found in the market. One, the conventional piano switch rated 15A and other, smaller switch rated 15A but 10 times less expensive.



Do you think that the cheaper one would be capable of handling arcing well?

(Application: Switching a 0.5 HP motor)

 

Also, when an AC motor is rated at 3A. Does it mean that the current drawn at all times remains within 3A? Doesn't it vary while switching ON/OFF?

 

Do you think that the cheaper one would be capable of handling arcing well?

Any switch rated for more amps than you motor draws would work.

Your over complicating a simple concept.

 

Your over complicating a simple concept.

Haha..Just being careful since this is not my domain..

 

Also, when an AC motor is rated at 3A. Does it mean that the current drawn at all times remains within 3A? Doesn't it vary while switching ON/OFF?

3 amps is a nominal rating when the motor is supplied with the nominal voltage and a full mechanical load.

At any constant mechanical load, if you give the motor less voltage then the current will be less. If you give the motor more voltage then the current will be more.

If you let the motor spin freely then the current will be less. If you clamp the motor shaft tight then the current will be more.

A motor will typically need some extra energy to get started, so you may see a short interval of higher current just as it turns on.

When turning off some of the energy inside the motor will need to come out so they may give a kick in the voltage. Using a simple switch as you do that should not be a problem.

 

Generally the rating shown on the relay is for a resistive load, motor relays are also rated in HP.
The ratings on your relay are for three different body standards as shown.
Max.