Waterfall & Motor Overload!!

[OnTheTools]

As part of a large waterfall installation I'm installing a single phase 0.75kW motor with time clock and need advice on the overload setting please! I was told anything above 0.5hp/0.37kW required a contactor with thermal overload?!

I'm aware the 3 phase calculation would be...
kW/ Vl x sqrt 3 x p.f but I'm unsure of what to do on a single phase installation.

Does it even require a contactor would you guys just wire it straight up from the time clock? Help and thanks!

 

[rapparee]

If a 750w motor was 80% efficient it would be 750/0.8=937.5w

 

[Marvo]

Yes, a motor is not 100% efficient. If it was then in theory the 0.75kw of output power that's stated on the motor could be produced using 0.75kw of electricity as per Tel's example calculation stated earlier.

 

[Knobhead]

A few words of advice for the OP

A/ read what’s on the motor plate.
B/ don’t take on work you can’t do.
C/ don’t expect an equivocal answer from the internet.

 

[shanky887614]

A few words of advice for the OP

A/ read what’s on the motor plate.
B/ don’t take on work you can’t do.
C/ don’t expect an equivocal answer from the internet.

read the plate carefully, quite often they state the requirements for single phase or 3phase

 

[Marvo]

read the plate carefully, quite often they state the requirements for single phase or 3phase

Nearly all 750w squirrel cage motors that are single phase won't run on 3-phase. The winding arrangement is very different, single phase motors will usually only have 2 windings and at least one capacitor.

 

[Knobhead]

When you get to a motor that size sometimes you need a magnifying glass of be a contortionist to see it.

 

[shanky887614]

Nearly all 750w squirrel cage motors that are single phase won't run on 3-phase. The winding arrangement is very different, single phase motors will usually only have 2 windings and at least one capacitor.

thanks for that, the smallest ive ever worked on is a 1.2kw.

 

[ackbarthestar]

As part of a large waterfall installation I'm installing a single phase 0.75kW motor with time clock and need advice on the overload setting please! I was told anything above 0.5hp/0.37kW required a contactor with thermal overload?!

I'm aware the 3 phase calculation would be...
kW/ Vl x sqrt 3 x p.f but I'm unsure of what to do on a single phase installation.

Does it even require a contactor would you guys just wire it straight up from the time clock? Help and thanks!

How large is a large waterfall? - probably better to have a synchronized on-line auto-switched 3-phase generator, then you could get a FIT from the supplier. Starts to get a little more complicated and probably requires a little more experience to install.

 

[Knobhead]

When I first noticed this thread I thought I may be something interesting. Maybe a Clarkson style 75KW Mono pump.

0.75kW will be a trickle.

Do we know if the motor is 3Ph or not?

 

[rapparee]

When I first noticed this thread I thought I may be something interesting. Maybe a Clarkson style 75KW Mono pump.

0.75kW will be a trickle.

Do we know if the motor is 3Ph or not?

Considering he is asking for single phase equation, it would suggest the pump is single phase

 

[ackbarthestar]

"When I first noticed this thread I thought I may be something interesting. Maybe a Clarkson style 75KW Mono pump.

0.75kW will be a trickle.

Do we know if the motor is 3Ph or not? "
​

Well, the OP states that he's installing a single phase motor. I suspect he might want to drive the waterfall into a larger one or wants to pump some of the water off into another reservoir.
I think the OP needs to continue the conversation so that we may be able to get a picture. Another thing we should know is :
a/ Head of water
b/ flow rate