Flywheels and AC Motor Inrush Current

Thread Starter

Schmiddr

Joined Feb 21, 2021
5
I have a customer who run a site that has many many AC motors of varying sized. When the larger ones start the inrush current is so much that it sets the utility rates for the month. Is there a way of using flywheel technology to assist in offsetting the facility’s peak current loads and therefore reducing the peak demand charges they currently experience?
 

MaxHeadRoom

Joined Jul 18, 2013
23,126
A flywheel will increase consumption due to the initial added to torque required to start the motor revolving.
If 3ph AC, look at star/delta starting. if possible.
Max.
 
Is this a NA or EU installation? In NA 3 phase motors are predominantly 9 lead; permanent wye or delta. Only 12 (or 6) lead motors with all winding terminations exposed are suitable for connection to star-delta starters. They're pretty rare these days.

What sort of controllers are we talking about here? Big centralized MCCs, individual machines with their own combo starter-disconnects, industrial control panels? If we're just concerned about a handful of 100+ horse motors, retrofitting individual soft-starters would probably be most economical.
 
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Thread Starter

Schmiddr

Joined Feb 21, 2021
5
A flywheel will increase consumption due to the initial added to torque required to start the motor revolving.
If 3ph AC, look at star/delta starting. if possible.
Max.
I should have been more specific. Im referring to flywheel energy storage systems upstream from the motors.
 

Thread Starter

Schmiddr

Joined Feb 21, 2021
5
Is this a NA or EU installation? In NA 3 phase motors are predominantly 9 lead; permanent wye or delta. Only 12 (or 6) lead motors with all winding terminations exposed are suitable for connection to star-delta starters. They're pretty rare these days.

What sort of controllers are we talking about here? Big centralized MCCs, individual machines with their own combo starter-disconnects, industrial control panels? If we're just concerned about a handful of 100+ horse motors, retrofitting individual soft-starters would probably be most economical.
the site(United States, California) has mainly AC motors to facilitate dry bulk goods conveyance to the motors turn on and stay on. There is no stop and go like a machine. We have targeted individual motors for VFDs and that helps but most of everything are tan though several MCCs.
 
Without knowing exactly how many motors you're looking at, it's probably going to come down to a matter of weighing the economics of installing soft starters at each motor or swapping out the MCC buckets themselves for ones with soft starters or VFDs. You could possibly look into softer starting motors like NEMA design 'D' if speed uniformity and efficiency are not concerns and they're only starting infrequently - but that's probably more trouble than it's worth.

What about the control scheme for the conveyor system? Is it properly configured to perform a staggered startup rather than putting all the motors across the line at once? Configure the first motors in the sequence to start D.O.L., then put the last six or so on soft starters to minimize peak demand?

Without knowing exactly what sort of site this is, a trick I've heard of farmers pulling is starting big motors (grain dryers, etc.) on a diesel generator set, then transferring them to utility power.

Lastly, on the conveyor projects I've been around recently they've been installing 'smart motors' exclusively - motors with integrated VFDs and remote communication protocols. Maybe something to think about if you can get some money back out of the existing motors secondhand? SEW Eurodrive makes them, I think. Occasional issues getting the longer braking times to play nice with the watchdog timers in the PLC program and a couple of bent power/data pins during installation now and then but otherwise not too many other issues I've heard about.

They look like bigger versions of this:
https://i.ebayimg.com/images/g/uLIAAOSwzxBevt3Q/s-l640.jpg

Got this little dongle that plugs into the pickerhead:
https://www.maxodeals.com/media/cat...9b1e35df139433887a97daa66f/i/m/img_3341_1.jpg
 
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Thread Starter

Schmiddr

Joined Feb 21, 2021
5
Without knowing exactly how many motors you're looking at, it's probably going to come down to a matter of weighing the economics of installing soft starters at each motor or swapping out the MCC buckets themselves for ones with soft starters or VFDs. You could possibly look into softer starting motors like NEMA design 'D' if speed uniformity and efficiency are not concerns and they're only starting infrequently - but that's probably more trouble than it's worth.

What about the control scheme for the conveyor system? Is it properly configured to perform a staggered startup rather than putting all the motors across the line at once? Configure the first motors in the sequence to start D.O.L., then put the last six or so on soft starters to minimize peak demand?

Without knowing exactly what sort of site this is, a trick I've heard of farmers pulling is starting big motors (grain dryers, etc.) on a diesel generator set, then transferring them to utility power.

Lastly, on the conveyor projects I've been around recently they've been installing 'smart motors' exclusively - motors with integrated VFDs and remote communication protocols. Maybe something to think about if you can get some money back out of the existing motors secondhand? SEW Eurodrive makes them, I think. Occasional issues getting the longer braking times to play nice with the watchdog timers in the PLC program and a couple of bent power/data pins during installation now and then but otherwise not too many other issues I've heard about.

They look like bigger versions of this:
https://i.ebayimg.com/images/g/uLIAAOSwzxBevt3Q/s-l640.jpg

Got this little dongle that plugs into the pickerhead:
https://www.maxodeals.com/media/cat...9b1e35df139433887a97daa66f/i/m/img_3341_1.jpg
When you mentioned farmers using generators duringvthe facility startup and then cutting over to the local utilities that is very simular to what Im envisioning. Except instead of a generator it would be a bank of flywheels. The facility does start up one motor after the other by the way. Its an issue of time. Nobody wants a multi-year transition to new VFD/Softstart for every motor in the facility if there is a way to achieve the same in one project.
 
On paper a sufficiently large motor-generator set would do what you describe. Big oldschool synchronous motor and a three phase generator would have enough mass to totally absorb the inrush from a couple of tiny 1-3HP conveyor motors. Of course then you have to soft start the synchronous motor. Chicken and egg. Then there's no-load and nameplate current to consider. Wouldn't pay to use a motor that draws more current at idle than the peak demand of the conveyor system. Cost of installing an MG set and re-feeding all the MCCs vs slowly replacing the buckets overnight or on weekends.

I believe the military does something similar for their critical power needs. Just enough stored energy for a UPS/generator set to take over or ride out the blip whenever an exploding squirrel trips the utility recloser.
 
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