Using One Contactor For Starting Two Motors

[AB2005]

Hello

 

I want to start two geared motors each 1HP by using only one contactor and two overloads for each motor. It means the out put of contactor will be distributed into two lines. These motors start two belt conveyors.

Is this method is ok? Any technical issue?

 

[Tua]

Hello!

May be it is better to use two contactors and one control signal? But the powers of motors are very little and I think you won't have problem if you connect as you want.

[jraef]

It is a very common thing to do. Just realize that both motors will start and run together, and both overload relays must have their control contact wired in series with the contactor coil so that if either one overloads, the contactor will open. That also means of course, they will both shut down. If that is OK with you, then there is nothing wrong with doing that.

 

Probably not a big deal with a 1HP motor, but also keep in mind that whatever Short Circuit Protective Device you use (i.e. fuses or circuit breaker), must protect not only the total circuit, but each individual circuit as well. As I said, shouldn't be a problem at 1HP, but if you ever do this at larger HPs, sometimes the breaker necessary to protect the entire circuit ends up being too big for each individual motor. In that case, you need an SCPD for each motor as well as an OL device. That is why most people use the Motor Protection Switches on that kind of application, they provide both function for each motor.

[AB2005]

Dear Mr. Jraef

 

Thanks for replaying

Both motors are in a conveyor which would start and stop together. That’s why I am thinking to control these motors using a single contactor and two overloads. There is also an issue of spare spacing in panel.

 

[marke]

Make sure that the AC3 rating of the contactor is greater than the sum of the two current ratings from the two motors.

With small motors, it is dangerous to base the rating on the total KW rating of the two motors as the amps per KW is very high an variable with small motors.

 

Best regards,

[medo_ibiza]

so i think it all leads to take care of the AC3 rating for the contactor. and for the spare space of the panel i think u should take in mind the diffrence between low noise and high noise earth connections. that's because u'll be using small rating items to control these two motors and it could be affected by high noise part items. so u must use different busbar for these items on the panel too. and dont forget to connect the two O.Ls in series with the contactor coil to stop both motors when one of them overloads.

and go ahead

[AB2005]

u should take in mind the diffrence between low noise and high noise earth connections. that's because u'll be using small rating items to control these two motors and it could be affected by high noise part items. so u must use different busbar for these items on the panel too.

 

Hello My Friend

 

I couldn't understand your words. Please explain