003a breaker trips when loaded

[Guyfang]

OK. Lets get back on track here. Have you disconnected all cables from the load terminals and just left the garage cable on. And tested just THAT part of your circuit?

 

[G744]

Doing commercial electrical work in a lot of high-power broadcast facilities, I've always tried to make things foolproof.

The problem is fools are so damned ingenious!

Many times I've changed my modus operandi to try and keep things safe.

 

[2Pbfeet]

Doing commercial electrical work in a lot of high-power broadcast facilities, I've always tried to make things foolproof.

The problem is fools are so damned ingenious!

Many times I've changed my modus operandi to try and keep things safe.

Ain't that the truth! Me, included. I've done some really foolish things, and consider myself lucky to be here.

All the best,

2Pbfeet

 

[DieselDr]

OK. Lets get back on track here. Have you disconnected all cables from the load terminals and just left the garage cable on. And tested just THAT part of your circuit?

Finally. I'm going to do just that this weekend.
And to be clear with everyone, I DO HAVE A BYPASS SWITCH FOR THIS APPLICATION, I just don't have it installed yet.

 

[DieselDr]

OK after much rehabilitation of my replacement shoulder and little vacation over seas, I am back to working on this problem.
Now with nothing but an 220v extension cord from the generator to the air compressor (no load starting, no air in the compressor) it still instantly trips the A/C output breaker/switch.
I have a video of the gauges when I turn it on, but even editing it down to 10-15sec. long, the server says it's too big.
What do I need to check now?
I think it is the breaker/switch.
It does grunt for a split second and the voltage gauge spikes up some, when the load is applied and instantly trips the output breaker.

 

[DieselDr]

OK after much rehabilitation of my replacement shoulder and little vacation over seas, I am back to working on this problem.
Now with nothing but an 220v extension cord from the generator to the air compressor (no load starting, no air in the compressor) it still instantly trips the A/C output breaker/switch.
I have a video of the gauges when I turn it on, but even editing it down to 10-15sec. long, the server says it's too big.
What do I need to check now?
I think it is the breaker/switch.
It does grunt for a split second and the voltage gauge spikes up some, when the load is applied and instantly trips the output breaker.

Also the FLA on the motor is 23-22 which should be well within the capacity of the generator.

 

[Scoobyshep]

It's not the FLA you need to look at right now. It's the inrush. They can take as high as 10 times the FLA on startup

 

[DieselDr]

It's not the FLA you need to look at right now. It's the inrush. They can take as high as 10 times the FLA on startup

As posted in this thread earlier,
L1 was 38A and L3 was 36A.
Any help?

 

[2Pbfeet]

As posted in this thread earlier,
L1 was 38A and L3 was 36A.
Any help?

In rush can last a fraction of a cycle to several cycles, and most DVMs do not capture all of it. So, I would regard the 38A as a lower bound. Basically, I suspect that you probably need a soft start or a VFD on that motor. As @Scoobyshep wrote, in rush currents can easily be 5-10X FLA, which would be more than enough to trip your breaker. There is the faint possibility that the breaker isn't 100%, but even if it were, I would expect and hope that it would kick out on a 5HP motor start. While some folks manage to start motors that large, in my book, it is not reasonable to expect that it should work.

My $0.02, get a soft start or VFD.

All the best,

2Pbfeet

 

[G744]

Ratings are one thing, reality another. A lot like "The map is not the territory"

Just a simple question: What brake HP is the engine in the genset rated at?

An inrush amperage, even X5, will easily run over a hundred Amperes for a very short time. 100A X 230V = 23kW. At 760W per HP, that equals some 30 HP.

 

[rickf]

I am no expert on this but I doubt there is a 100 amp inrush on a 5 hp motor. I have been running a 5 hp compressor for 20 years on a 15 amp breaker. The wiring is 6 gauge but the breaker got swapped with my 50 amp for my welder. I had planned to put in a 30 amp breaker for the compressor but it just never got done. I recently switched to a 75 year old compressor that is quieter and gives more air but the motor on that one is a 75 year old 3HP and it pulls a lot of amperage. It will pop the breaker if it is extremely cold out but otherwise it does not. Now, if I remember my Ohm's law that 15 amp breaker will hold 3,300 watts on 220. If they draw 100 amps at start up that breaker would not stand a chance. And not only that the compressor cannot be drawing 25 amps running on a 15 amp breaker. I think that 25 amp rating is at full rated load.

 

[Scoobyshep]

I

I am no expert on this but I doubt there is a 100 amp inrush on a 5 hp motor. I have been running a 5 hp compressor for 20 years on a 15 amp breaker. The wiring is 6 gauge but the breaker got swapped with my 50 amp for my welder. I had planned to put in a 30 amp breaker for the compressor but it just never got done. I recently switched to a 75 year old compressor that is quieter and gives more air but the motor on that one is a 75 year old 3HP and it pulls a lot of amperage. It will pop the breaker if it is extremely cold out but otherwise it does not. Now, if I remember my Ohm's law that 15 amp breaker will hold 3,300 watts on 220. If they draw 100 amps at start up that breaker would not stand a chance. And not only that the compressor cannot be drawing 25 amps running on a 15 amp breaker. I think that 25 amp rating is at full rated load.

It's absolutely possible.

Not to mention these are apples to oranges. Your standard household breaker is a thermo mag breaker (thermo being the slow overload trip, mag(netic) being the inrush. Their trip curve (time vs current) is rather forgiving (especially GE breakers).

Now for the breaker used on the 002 and 003, by design of the breaker (there's another really good thread on them) tend to be a bit more sensitive to the mag inrush, especially with the voltage droop from a heavy start load.

Out of curiosity @DieselDr have you loaded the set to 100% with other devices?

 

[DieselDr]

I

It's absolutely possible.

Not to mention these are apples to oranges. Your standard household breaker is a thermo mag breaker (thermo being the slow overload trip, mag(netic) being the inrush. Their trip curve (time vs current) is rather forgiving (especially GE breakers).

Now for the breaker used on the 002 and 003, by design of the breaker (there's another really good thread on them) tend to be a bit more sensitive to the mag inrush, especially with the voltage droop from a heavy start load.

Out of curiosity @DieselDr have you loaded the set to 100% with other devices?

All I have that is 220v are my air compressor, Mayer 50lb. Power hammer and 2 welders. The compressor and hammer have identical 5hp motors on them.
Everything is single phase.
In my research on VFD's ,the output is 3 phase for most of them, correct? And you would of course need a 3ph inverter-rated motor.
When I get time I will try welding with the generator supplying the power and see what happens.

 

[Scoobyshep]

All I have that is 220v are my air compressor, Mayer 50lb. Power hammer and 2 welders. The compressor and hammer have identical 5hp motors on them.
Everything is single phase.
In my research on VFD's ,the output is 3 phase for most of them, correct? And you would of course need a 3ph inverter-rated motor.
When I get time I will try welding with the generator supplying the power and see what happens.

You can get smaller vfds that are single phase output. Not sure how well that will play with a start run wound motor.

 

[DieselDr]

All I have that is 220v are my air compressor, Mayer 50lb. Power hammer and 2 welders. The compressor and hammer have identical 5hp motors on them.
Everything is single phase.
In my research on VFD's ,the output is 3 phase for most of them, correct? And you would of course need a 3ph inverter-rated motor.
When I get time I will try welding with the generator supplying the power and see what happens.

Would this work?
I don't want to spend $200-1000 on something, just to find out there is something wrong with the generator itself. I'm not a rich man.

 

[2Pbfeet]

Would this work?
I don't want to spend $200-1000 on something, just to find out there is something wrong with the generator itself. I'm not a rich man.

Soft starts are definitely usable, given the size of your capacitor start motors, probably a cost effective way to go.

VFDs do much better starting induction motors, but yes, you can certainly get them for single phase in/out.

All the best,

2Pbfeet

 

[glcaines]

Is there a reason not to install the soft start directly on the generator and run all single phase output through it?

 

[2Pbfeet]

Is there a reason not to install the soft start directly on the generator and run all single phase output through it?

Yes, there is a reason why you should not connect a soft start unit directly in to the generator. The soft start units need to be wired directly to the start windings on the motor, and most soft start units include a bit of optimization for the particular motor that they are connected to. (Take a close look at the photo above.)

All the best,

2Pbfeet

 

[G744]

Something a bit hard to wrap your head around is the difference between the source impedance of the grid and a genset.

Impedance is a term describing the resistance portion of an AC circuit. Remember, any type of resistance in a circuit will lower the amount of energy. The lower the resistance, the more power can be delivered.

In other words for instance, a 25A breaker will support more inrush time on the grid than the same breaker on a genset (unless it a BIG SOB).

I know, it doesn't seem to make sense, but that is the way it works.

The resulting sag induced by starting a single-phase motor will 'ask' for more energy. This can result in voltage droop, which in turn causes an 'ask' for more amps to make up the motors' demand in kW.

The grid has reserve most gensets can't even get close to.

 

[DieselDr]

Something a bit hard to wrap your head around is the difference between the source impedance of the grid and a genset.

Impedance is a term describing the resistance portion of an AC circuit. Remember, any type of resistance in a circuit will lower the amount of energy. The lower the resistance, the more power can be delivered.

In other words for instance, a 25A breaker will support more inrush time on the grid than the same breaker on a genset (unless it a BIG SOB).

I know, it doesn't seem to make sense, but that is the way it works.

The resulting sag induced by starting a single-phase motor will 'ask' for more energy. This can result in voltage droop, which in turn causes an 'ask' for more amps to make up the motors' demand in kW.

The grid has reserve most gensets can't even get close to.

OK guys ,I tested it with my welder and it does power it fine.
Now while welding, the %of load Guage goes to 50-60. But the frequency gauge does not move. The only time it moves is just slightly up from zero when starting or when you shut down the generator. Why is it not indicating the hz output?