Power Consumption

Ref your query, I think that you don't need a formula, you will need an instruments like Fluke-1735 Power Logger (or similar) to take all the informatiom from the motors.

Cordially yours, Arturo

It looks like there is an opportunity for improving the bottom line of this organisation. If corporate nagging techniques don't work, consider investing in time-switches and room occupancy sensors, assuming the organisation pays for electricity by the kWh?

Well, let's see. You're people are definitely wasting power, that's for sure.

If you're warehouse happened to be located in my factory, our boss would blow his top and put a grenade in each of the people's pants and threaten to pull the pin if everyone doesn't shape up.

All that and he won't even stop to ask how much power is being wasted. All he cares about is that power IS being wasted and he doesn't care how much.

So...don't ask how much, just stop the waste.

Before El Gato Del puts his two cents in, when I had a few minutes I searched the site and found where this had been discussed before and found the formula that I needed. And I passed that on to those concerned, and hopefully they put a few hand grenades down some shorts and pull the pins.

Thanks guys!

Jon

Consider adding some proximity switches & or photo beams so the conveyors don't run when empty, a few timers to complete run out would limit the complexity of such a set up

First off, technically the answer to your question would be "100%"!

If you are running motors that are not being used and don't need to run, the wasted power is 100% of the consumed power. I know that's probably not what you meant to ask, I was just being persnickety.

But if you don't have a way of actually measuring the unloaded power, you can guesstimate it fairly well by using 30% of the FLA. Most small AC motors will pull about 20% FLA when completely unloaded, but in your case you need to add some friction load just to move conveyor belts, so another 10% should cover it (unless you have some kind of unusual belting). In addition, your power factor will be really low, probably in the .3 range, when unloaded. So your kW would be 1.732 x (FLA x .30) x V x pf / 1000 = kW. So in your case, you have 1.732 x 2.33A x .3 x 480V x .3 / 1000 = approx. .174kW per motor, x 50 motors = 8.72kW of wasted power. If you want to know the ENERGY wasted, take the kW x the unnecessary running hours. So if they are left running overnight for 8 hours a day, that's 70kWh per day, x 20 days per month, that's 1400kWh / month. If you pay 15 cents per kWh like we do here in California, that's $210 per month.

An easier solution than occupancy sensors or load sensors on each conveyor may be to put a power (kW) monitor on the power feeder to all the equipment in that room (assuming it's that simple) and look at the normal running kW. When the kW drops below that for a set time, say 30 minutes, shut it all down. Siemens makes a unit that would do that called a Simocode. You would need some sort of a device to kill power though such as a contactor or a circuit breaker with a shunt trip. Either that or use a master control relay wired to each of the motor starters so that it shuts each one off.

Thanks for providing a helpful, direct answer to the original poster. IMHO, too many of the replies I see here are unprofessioanl rants that reflect poorly on engineering in general.

Thanks for the input.

Talked to my supervisor and since the starters and contactors for the motors are in the cabinet with the PLC equipment, it will be easy to hook them in. Since it is the older, un-renovated part of the plant, we would have to run photo eyes to the conveyors and program in sleep timers to shut them off. We already have the power monitoring equipment, and that is where I got the power factor for my calculations after I found the proper formula.

So it looks like I will gain a new project to spend some money to save some money.

As a heads up,you may want to look at what it takes to start back up. Some systems are left in operation because the power is cheaper than re-commissioning the equipment on a daily basis. Unless you have commissioned the system I would do some research before you shut down, the restart sequence could be more complicated than you realize. I assume your goal is to save the company money, also ask how much money it costs if the conveyor system doesn't operate for one day. There will be a day that a motor fails on starting. It would suprise me if the conveyors in your plant are running continuosly simply because nobody has thought of turning them off.

there are 2 ways you can cut down Waste and hence profit yourCo and/or yourself.

1. When running ,add automatically a 3Phase Capacitor of appropriate µF across 3 phases. Will now show P.F ~1.0 for each running motor.And line current is a known Low! Say I_idle1
2. Sensor can be set to MONITOR If that running motor stays at I_idle1 FOR>15 seconds . And hence to automatically Switch Off