An energy contractor sold management four PF525s for the four 10hp belt conveyors on the sort line last winter. The quote said 25 percent saving. Six months in and the kWh on the sub-meter for that MCC is flat, same as the six months before it, give or take weather.
The conveyors run at 60Hz all shift, line speed set by the machine downstream. I've been through the drive parameters, V/Hz, no boost, nothing odd in there and I had the sub-meter checked against a clamp so that's not it either and the contractor came in and told us to give it time.
Is there some energy mode on the PF525 I'm missing? Or was a belt conveyor at 60Hz all shift never going to save anything, because I have to say something in Monday's meeting?
What are the conveyors, belt, chain, roller? And what's the motor current on the drive display against the nameplate, with the line running as normal?
Belt conveyors, cases on them. Drive shows 9.8 A, nameplate is 14. About 70 percent loaded I think, steady all day, 60Hz all day.
Constant torque load at full speed. The drive hands the motor the same 60 Hz the line did, minus a couple of percent lost in the drive, so if anything the kWh went up a touch. The saving story belongs to fans and pumps, where power drops with the cube of the speed and you actually run them slower. A belt at fixed speed carrying the same cases has the same work to do, drive or no drive.
No parameter changes that. What you bought is soft starts and speed matching. Log kW per drive at 1 min and you'll see four flat lines.
The where the savings actually come from part is in this one: https://plctr.com/achieving-sustainable-manufacturing-with-plc-control-systems/
So the contractor's 25 percent was a fan number pasted onto a conveyor quote. Still nothing on the meter then.
Yes. Ask him which fans he had in mind.
Pulled a week out of the historian for the four drives. About 6 kW each, flat, all shift.
No saving to chase then. Constant torque at full speed, same cases on the same belts, and a drive can't do anything about that. They stay, mind, the soft start is worth it on its own: two of those motors stripped belts twice a year on the old starters and haven't since.
The contractor also quoted the two 40hp dust collector fans. Those could be worth it if we can turn them down when half the line is idle. Starting there next. Thanks scott, dan.
The fans are where the 25 percent lives. Trend them first, then decide.