Stacked FX-2524T's and PSX-240 strange noise +

[TomW]

Folks;

I have 2X Outback FX2524T's stacked like this:



Been running smooth for a few weeks, powering pretty much anything we throw at it.

Suddenly this afternoon while Amy was running the Vitamix blender (a 1300 watt load according to the Mate) making slushies to combat the heat we suddenly have the PSX-240 started making a loud 60 Hz hum and the leg the blender was on went dead. No tripped breakers in the system. No fault indicated on the FX's. I power cycled the FX's and it all came back up immediately and no power loss issues seen since. We have run the blender before on the system with no troubles or noise from the transformer. We ran it again and it makes the transformer hum  some times but not always but no power loss again. Normally, even with near max loading the transformer is not heard above the ambient noise in the area it is in such as Classic Fans and computer equipment fans. I tried it on the other leg and same noise. The 1800 watt water heater does not make it hum.

Any theories on what might be going on?

Thanks for any feedback

Tom

[Vic]

Hi Tom,

First,  I have none of the equipment that you have mentioned.
A 1300 Watt Blender is large.  And am sure that it uses a Triac motor speed control circuit,  which can increase the stalled rotor torque and peak currents,  especially when crushing ice.

Here, with our SW+ inverters,  VSR drills that are stalled when the trigger is gently pulled (reaming holes in steel,  or starting Hole Saws etc) causes a buzzing moan from the inverter supplying the current,  but,  so far,  no faults.

As you know,  it is very uncommon for an AC circuit breaker on the output of an medium to larger inverter to pop,  even with a dead short.  The inverters detect high load current,  kill the output,  perhaps try restarting a few times,  and then quit until reset.  Although,  normally one would expect that a Fault code would be recorded and a light would indicate the Fault -- I have no direct experience with OB inverters,  though.

This is just my drive-by opinion.   Guessing done for now.   Good Luck,  and keep cool.   Vic

[Robin]

The SW inverter acts quite different than the OB when it comes to current limit. The SW will hit the limit of about 110 amps and then turn off. It then tries again and turns off again. This all happens very quickly. After about 10 or 20 seconds of not being able to start the load, it just shuts off and then requires a manual restart.
The OutBack can do better since it is switching at 20KHz. The current limit is much lower on the OB, but the inverter never shuts off. It will hold the current at 70 amps until the load starts or the inverter shuts off. The OB doesn't wait very long to shut off though.
The blender is a motor, so will have out of phase current. The actual current spikes may be more than you can see. If you are using the Mate to make your current measurement, it will not capture the peaks.
Hope this helps.

[TomW]

Vic, Robin;

Thanks for the replies!

The Vitamix is a blender on steroids 120 VAC 11.5 amps. Variable speed and manual recommends starting on "low" and ramping up from there to the speed you desire for effect.  Supposedly it can blend a 2 inch hardwood dowel from the advertisements.

Between slow starting speed and frozen fruit it probably is pulling huge current that is lagging the voltage so the reported 1300 watts on the Mate is not at all accurate and may be a high multiple of the reading on the Mate. Perhaps the out of phase current is making the PSX-240 noise? I am not that concerned with the sound but I am concerned with the loss of power on one leg with no indication beyond "not energized" that there is a problem. And the concern over damage or some other fault indicated by the noise and loss of power on one leg.

I am kind of curious of how this configuration can even lose power on one leg and not the other with no open breakers as long as one inverter is energized? At least with no open circuit someplace.

I am just concerned there is a fault in the autotransformer I am aggravating with the blender. It is no big deal to just use the grid for the Vitamix as it is not run often or long and we still have it available.

So, boiled down the question becomes: Is there a fault that only appears with this load and will it eventually fail completely and how can it even lose one leg in this way as long as one inverter is energized?  It seems clear that as long as either inverter is energized it should provide both legs with 120 and 240 between the hots on the output of the autotransformer at a lower power?


Thanks for any responses.

Tom

[ChrisOlson]

It seems clear that as long as either inverter is energized it should provide both legs with 120 and 240 between the hots on the output of the autotransformer at a lower power?

Tom, that is correct.  You can't have either L1 or L2 dead if one inverter is running and the transformer is functioning.  What are you using for breakers on that transformer?  The reason I ask is because the breakers in our PSX-240 were bogus.  I had one that would trip with the handle still in the "on" position just by slamming the door on the utility room.  The vibration on the wall when I slammed the door would cause that breaker to open.

I replaced those breakers with a good old SquareD 30 amp two-pole (because they didn't have a 25 amp in stock).
--
Chris

[TomW]

Tom, that is correct.  You can't have either L1 or L2 dead if one inverter is running and the transformer is functioning.  What are you using for breakers on that transformer?  The reason I ask is because the breakers in our PSX-240 were bogus.  I had one that would trip with the handle still in the "on" position just by slamming the door on the utility room.  The vibration on the wall when I slammed the door would cause that breaker to open.

I replaced those breakers with a good old SquareD 30 amp two-pole (because they didn't have a 25 amp in stock).
--
Chris

Chris;

Not sure of the breaker make but it is the PSX-240 autotransformer in a case with breakers from Outback and unmodified. I had cycled those 2 ganged breakers right away as the first suspect and it didn't get the leg up so then I cycled the DC breakers on the FX's and it came back up.

I was pretty sure I should have both legs active with either FX running or both but have misinterpreted schematics before.

Thanks for the feedback.

Tom

[ChrisOlson]

Not sure of the breaker make but it is the PSX-240 autotransformer in a case with breakers from Outback and unmodified. I had cycled those 2 ganged breakers right away as the first suspect and it didn't get the leg up so then I cycled the DC breakers on the FX's and it came back up.

Well, if you're sure it was only one leg that was dead, that's weird.  A transformer is a pretty basic unit.  If it has power on the primary, short of a black hole or time warp or something sucking all the flux out of the core, it has to have power on the secondary too   
--
Chris

[TomW]

Well, if you're sure it was only one leg that was dead, that's weird.  A transformer is a pretty basic unit.  If it has power on the primary, short of a black hole or time warp or something sucking all the flux out of the core, it has to have power on the secondary too   
--
Chris

Chris;

Pretty sure. Amy paged me on the intercom to say the fridge, blender and a lighting circuit in the house were out. Equipment in my "office" / boars nest was still running so it was only one leg.

Perhaps I created a warp bubble and time displaced the energy to another region of space / time?

Kind of why I asked here as it made no sense to me. I am getting kind of old but hopefully not senile yet.

Thanks.

Tom

[ChrisOlson]

Perhaps I created a warp bubble and time displaced the energy to another region of space / time?

Yep.  Sun spots, strange magnetic fields from asteroids, narrow band power beam from an alien mother ship - something kept the Boar's Nest alive but it wasn't the inverters and transformer if one leg was dead.  We got the same setup you got, except replace the stacked inverters with a XW.  You can't lose just one leg, even if you physically unhook L1 or L2 from the inverter.  The transformer was making noise because of one inverter going offline and instead of just handling a leg imbalance, now it was supplying all the power to an out-of-phase load.  That makes the windings vibrate in it and our PSX-240 used to do that when we had it on the SW Plus 5548 for split phase power.

From that point, in order to keep one leg alive and the other goes dead, the breaker to the transformer has to trip or go open.
--
Chris

[TomW]

From that point, in order to keep one leg alive and the other goes dead, the breaker to the transformer has to trip or go open.
--
Chris

Chris;

Well, whatever happened, I am like a nervous hen watching her chicks when the cat is around now. Maybe it was the breakers tripping without "looking" tripped but cycling them should of brought it back but did not.

I will be watching it closely and the blender goes on the grid when needed.

Up to this issue, we have been super happy with this upgrade. Sadly, the weak link is batteries now. This addiction never ends! Even with them being a bit aged and weak we can nurse it along quite well as long as we don't go off grid.  Survival level off grid would be easy now but needs are different, then. We like stuff like AC, TV time and long hot showers all provided by electricity and not high priorities if they are not delivering electricity for whatever reason.

Our "access and delivery" fees nearly exceed our KWH costs now. When that gets reversed I may convince the CFO we should invest in a couple tons of lead and hack off the meter pole and return it to Hawkeye REC.

Thanks.

Tom

[firerescue712]

Did you check for power on both sides of the breakers?  Sometimes, a breaker's switches will not visibly indicate tripped, but the breaker will be tripped internally.  I have seen fires from this occurrence.  I would try a different breaker to see if it resolves the situation.  Like stated in the above posts, there should be power, or no power.  If the breaker proves to be working properly, start troubleshooting the circuits down the line to make sure all receptacles are energized and the wires are tightly connected.  I have seen loose wires feeding to and from a receptacle.  They are making contact with the connections, but are not secure.  When a load is placed on the circuit down the line, the wiring starts heating and arcing in the wall box.  This is from first hand experience.  Be safe, my friend.

[TomW]

Did you check for power on both sides of the breakers?  Sometimes, a breaker's switches will not visibly indicate tripped, but the breaker will be tripped internally.  I have seen fires from this occurrence.  I would try a different breaker to see if it resolves the situation.  Like stated in the above posts, there should be power, or no power.  If the breaker proves to be working properly, start troubleshooting the circuits down the line to make sure all receptacles are energized and the wires are tightly connected.  I have seen loose wires feeding to and from a receptacle.  They are making contact with the connections, but are not secure.  When a load is placed on the circuit down the line, the wiring starts heating and arcing in the wall box.  This is from first hand experience.  Be safe, my friend.

712;

I will troubleshoot further if it happens again but at the time I had tunnel vision on getting it back up. I may have a couple spares for the breakers and may just swap them to "be sure" if I have them. I didn't realize until later that it was such an unusual failure mode.

Thanks.

Tom

[ChrisOlson]

Did you check for power on both sides of the breakers?  Sometimes, a breaker's switches will not visibly indicate tripped, but the breaker will be tripped internally.

Yep - that's exactly what happened to the breaker on one leg in our PSX-240.  I just eliminated the breakers in the transformer itself by bypassing them internally in the PSX-240 and wiring each leg to a 30 amp SquareD QO two-pole in our power distribution panel.  Haven't had a problem since with the transformer going offline.

In addition, that weak breaker caused more leg imbalance than we should've had, even when it was "ON".  After applying my "fix" it keeps the legs on the inverter and generator within a couple amps, even with 20 amp imbalance to the loads when the inverter is operating in Gen Support mode.
--
Chris