ABB ACS580 Flying Start issue

[Brew Chip]

I'm in the midst of commissioning a number of these units and I'm having a trouble with a flying (re)start. The short background is that my PLC is using Modbus to control a blower motor that is integral to a third-party heater system. The heater sends me a blower request; I send 1151 in the control word to start the drive and send the heater an ACK when the blower is up to speed.

The issue is that when the heater short-cycles, the drive won't spin back up until it comes to a complete stop. It's a big blower and the spin-down usually takes so long that the heater throws an alarm. (I can't/don't want to go down the rabbit hole of the short-cycle itself. That's in said third-party's court.) We have enabled parameters for a flying start and it works as desired when we put the drive in local control, but not from Modbus commands. My AOI for drive control is pretty simple, I send 1151 to run, 1150 otherwise, and no logic on my end is checking for a full stop before sending a start. I see that 1150 is explicitly a ramp to stop command, does flying start only work when coasting (which would be command 1149)?

 

[TWS]

manual: Note: If parameter99.04 Motor control mode no flying start or automatic restart is possible unlessparameter21.19 Scalar start mode is set to Vector.21.19 Scalar start mode. Automatic start mode(page 115).21.02is set to Scalar is set to Automatic

 

[Brew Chip]

manual: Note: If parameter99.04 Motor control mode no flying start or automatic restart is possible unlessparameter21.19 Scalar start mode is set to Vector.21.19 Scalar start mode. Automatic start mode(page 115).21.02is set to Scalar is set to Automatic

Yep, first thing we verified.

 

[Brew Chip]

After putting out some of the more pressing fires, I was finally able to get a hold of ABB tech support and got a bit of a head scratcher response (emphasis mine):

This is normal and is part of the ABB state machine. You would have to wait till the drive stops before they can restart. (Control word Off1 (bit 0) states "Stop along currently active deceleration ramp. Proceed to OFF1 ACTIVE; proceed to READY TO SWITCH ON unless other interlocks (OFF2, OFF3) are active.")

However there is a workaround:

Initial state before a start command = 1150 Jog or standard Run Command = 1151 Stop command from either run or jog = 1087 (remove only bit 6 of Control Word, (RAMP_IN_ZERO) this forces the input to the ramp generator to zero, and thus causes the drive to ramp to zero speed. Once the drive reaches zero speed, it will remain in a modulating state, thus the PLC must monitor actual motor speed and once at zero speed (or below a low speed value) for a period of time, then remove bit 0 and reset bit 6 (1150 dec) and the drive will shut off. If a restart is desired after Bit 6 has been removed from the control word and the drive is ramping to zero speed, then simply reapply bit 6 (1151 dec) and the drive will regain its normal running state.

First head scratch was figuring out where the punctuation was supposed to be, but my read was that 1150 is the initial state, 1151 is standard run or jog, and 1087 (i.e. 1151 - 2^6) is "run, but set the ramp input to 0." So this person is suggesting to use 1151 to run, 1087 to stop, and either wait for speed feedback 0 before setting the command to 1150 idle OR restart at any point with 1151 again. The problem with this is that this is a blower motor and we explicitly want it to coast to stop, not ramp.
Second head scratcher is why would I need a workaround to use a properly enabled feature? If you have a flying start option and it is enabled, why would your state machine still require a complete stop before restarting? Pardon the emphasis, but this has me irked. I find it irksome.

I've written back and am still waiting on a reply, but will follow up (hopefully) one last time when I (hopefully) have a resolution. Unless someone else has some experience (or a working AOI!) they'd like to share.

B.C.