View Full Version : Back- E.M.F. questions

11-01-2017, 11:12 AM
Hi all

I am trying to figure out if the following configuration would work.

I have acquired 3 x 1606-XLS480EC (24V, 20A) PSU’s, which I plan to wire in series to give me 72V, 20A PSU, this would be connected to the Leadshine AM882 drive which will drive my 85BYGH450D-008 Nema 34 1090 oz-in motor.

On reading thru the PSU manual they have the following:

Loads such as decelerating motors and inductors can feed voltage back to the power supply. This feature is also called return voltage immunity or resistance against Back- E.M.F. (Electro Magnetic Force).
This power supply is resistant and does not show malfunctioning when a load feeds back voltage to the power supply. It does not matter, whether the power supply is on or off.
The maximum allowed feedback voltage is 34Vdc. The absorbing energy can be calculated according to the built-in large sized output capacitor which is specified in chapter 8. If the feedback voltage gets higher than 34Vdc, the power supply responds with a shut-down and a subsequent start-up attempt.

Great, this will resolve my worries on the Back- E.M.F. , however on the connection information for the serial connection there is this caveat

Note: Avoid return voltage (e.g. from a decelerating motor or battery) which is applied to the output terminals.

This has got me worrying that my proposed configuration will be an issue.

My question is, what is the role of the step driver (AM882) with regards to the Back- E.M.F. Will it pass this through to PSU and cause issues?


11-01-2017, 07:32 PM
With switched PSU's they don't handle back emf vety well as they don't have large capacitors to absorb it. That's why most of us build our own and put nice big capacitors to smooth the output voltage and also handle any back emf from deceleration.

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