Single phased Powerflex 525

Thanks Geospark for correcting me you are correct, I blew through reading post and left with single phasing, And I thought it odd all the post not mentioning overload. Then Later he mentioned brake on while running, that would increase current and overload would come in to play. After re-reading yes you are correct. And a very good explanation of the input section or diode section of the drive and DC Bus. Sorry, juggling to many things and not paying close enough attention.

Geospark said:

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For a single phase supply, the PowerFlex 4 and 520 series drives must be derated 35% on the output load but the larger 400 series drives do not support derating (Frame G & H).

For derating the 7 series drives it's the temperature of the diode/SCR (Silicon Controlled Rectifier) front end that must be kept low (25°C/77°F) to protect the bus caps from the excess bus ripple. That's why they must be further derated to 50% on the output load.
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Just wanted to make a small but important correction.
The PF4 and 5 series (up to and including 15HP@240V) are designed without DC bus chokes, so they must be de-rated TO 35%, not BY 35%. It is these small drives that have to worry about the temperature of the bus caps, because the single phase ripple makes them work harder. So if you have a VFD designed for 3 phase and 10A, it is good for 3.5A if the input is single phase. This is true for all VFDs that do not have DC chokes, as most Asian drives are designed (because all capacitors come from the same companies that make drives, so caps are cheaper for them). If you select a drive that STATES it is rated for single phase input, the drive has more capacitance built in already. Alternatively if you want to use them at a 50% de-rate, you must keep them at 25C instead of 50C. The Air Conditioner to do that would be more money than the larger drive, but if you already have an A/C, then that's an option.

The PF7 series all have DC bus chokes that do some of the DC ripple smoothing work, so they only need a 50% de-rate if given single phase, no temperature de-rating is necessary.

No VFD is good with only a 35% de-rate, because the diodes themselves have to handle 173% more current on a single phase feed. So that alone is a 58% de-rate, then we add the other 8% to help out the diodes (on drives with DC chokes).

AkaHammer said:

Thanks Geospark for correcting me you are correct...

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It's all good. Hey, even I need correcting too!

jraef said:

Just wanted to make a small but important correction. The PF4 and 5 series (up to and including 15HP@240V) are designed without DC bus chokes, so they must be de-rated TO 35%, not BY 35%.

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Thanks for that and good on you. I did know it was "to" when reading source material but I wrote it as meaning "by" while hastily throwing that together.

Yes the DC bus choke acts like a temporary buffer to control the precharge of the bus, helping to protect the capacitors and avoid ripple. The older PF70's don't have chokes until Frame C, but after that all PF7 have them alright. "Other" drive manufacturers definitely tend not to add chokes to their cheaper models as it drives the prices up and also it's another selling point when deciding whether to go big or go home.

Regards,
George

jraef said:

There is nothing in A-B (6 pulse) drives that looks at the actual incoming line voltages, which makes them all suitable for using on single phase (with the proper de-rating). What the drives look at is the DC bus ripple and when excessive, they trip, then the trip tells you it was a phase loss. But if the load is light, it is the same effect as de-rating, so the drive doesn't know that it lost a phase. On a PF52x drive, the load will have to be less than about 30% of the rating of the drive, on the PF7xx drives, about 50%. So if your load was very light compared to the size of the drive, it didn't care that a fuse had blown, at least not yet. No harm, no foul.

A lot of drive mfrs are doing this now, because having a phase monitor on the front-end is basically pointless and limits your ability to sell it to people who want to use it as a phase converter.

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Snippet from the datasheet