Varying Speed AC Generator to Steady DC

Tony Stewart · Oct 11, 2023

This is not a field-regulated alternator and the AB20L datasheet specifies the source must be 5 HP or the warranty is void due to damage from delays in thermal protection. Air pressure power, I believe is the product of pressure (P)* air flow volume (V).

The no-load V/f should be constant and the max load power should be at 50% max RPM.
But I recall they rate max at power 60 Hz.
What is the [psi / watt] at 33 Hz.

Soul21 said:
The prime mover is pressurized air (150 psi - 190 psi). The generator is a 240 v 60hz 10 amp motor (wanco AB20L) The load below is a test load 120v 500 watt heater.

The real load will be a bank of 12 volt batteries wired to be 24 volt. I am struggling to understand why the frequency/rpm remains the exact same even though the prime mover is increasing.

With load:
150 psi / 55 volts / 0.9 amps / 33 Hz
170 psi / 78 volts / 2.1 amps / 33 Hz
190 psi / 112 volts / 4.1 amps / 33 Hz

Without load:
150 psi / 85 volts / 37 Hz
170 psi / 168 volts / 47 Hz
190 psi / 235 volts / 59 Hz

						Pwr Max=	2400
PSI	V [volts]	I [Amps]	f [Hz]	psi/VA	f / fo	Pwr [W]	P / Pmax
150	55	0.9	33	3.03	89%	49.5	2.1%
170	78	2.1	33	1.04	70%	163.8	6.8%
190	112	4.1	33	0.41	56%	459.2	19.1%

PSI	V [volts]	no load	fo (Hz)	V / f
150	85	“0”	37	2.30
170	168	“0”	47	3.57
190	235	“0”	59	3.98

Conclusion not enough Prime Mover source power to generate 2400 VA out at 190 psi. perhaps suboptimal torque conversion 1:1 and needs pulleys. Or better use a field regulated Alternator.

Soul21 · Oct 11, 2023

Tony Stewart said:
Conclusion not enough Prime Mover source power to generate 2400 VA out at 190 psi. perhaps suboptimal torque conversion 1:1 and needs pulleys. Or better use a field regulated Alternator.

So if I had enough prime mover source power the hertz would get to 50?
Why should max load power be at 50% max RPM?

rjenkinsgb · Oct 11, 2023

Soul21 said:
Happy to share pictures. If there is something specific I can call Wanco and get that information. They are very helpful. Currently the second unit purchased will have the AB30T on it. The customer like the idea of AC due to the long line run from gernator.

OK, so it's not a "Motor" as you originally said.

It is a purpose built, internally regulated, synchronous alternator.
And totally unsuitable for your purposes.

Those are designed to run from such as a governed engine, so the shaft speed is near constant at the required RPM. Under those conditions, the output voltage would be regulated and not vary significantly with changes in load.

Nigel Goodwin · Oct 12, 2023

rjenkinsgb said:
OK, so it's not a "Motor" as you originally said.

It is a purpose built, internally regulated, synchronous alternator.
And totally unsuitable for your purposes.

Those are designed to run from such as a governed engine, so the shaft speed is near constant at the required RPM. Under those conditions, the output voltage would be regulated and not vary significantly with changes in load.

So, 40 posts before he actually gives us any information - seems typical for these kinds of posts!. If he'd done that in post #1 it would have saved wasting everyone's time!.

Soul21 · Oct 12, 2023

2 pictures worth 40 posts. Nigel - lets not get crazy here. I have been providing information since posts #1. Any information that was asked for was provided.

I did say it was a generator on my very first post. Admittedly I assumed motor vs generator didn't matter.

Rjenkinsgb - I thought these are all things we already knew. I am looking to solve the issue by either (a) replacing the generator with something more applicable or (b) putting a device in line to convert the power to something usable.

In regards to option B. Is there a reason something like this wouldn't work? The BALMAR Digital Duo Charge 12V/24V Regulator

shortbus= · Oct 12, 2023

This type of thing is being done, but not by someone that has no clue.

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rjenkinsgb · Oct 12, 2023

Soul21 said:
In regards to option B. Is there a reason something like this wouldn't work?

That's a slave charge unit, from one battery that is being charged, to another. You don't have one charging system yet..

The vehicle alternator is the only type of device that I know will work over a varying speed range such as your turbine unit has.

It's certainly the cheapest and simplest, as it has the battery charge control system built in.

(And I think it's a safe bet that they are far cheaper than the big synchronous generators you have been trying!)

Other devices could work, but you then end up with the same rectification - voltage conversion - charge regulation etc, stages that add to cost and complexity.

Tony Stewart · Oct 12, 2023

Tony Stewart said:
This is not a field-regulated alternator and the AB20L datasheet specifies the source must be 5 HP or the warranty is void due to damage from delays in thermal protection. Air pressure power, I believe is the product of pressure (P)* air flow volume (V).

The no-load V/f should be constant and the max load power should be at 50% max RPM.
But I recall they rate max at power 60 Hz.
What is the [psi / watt] at 33 Hz.

Pwr Max=
2400
PSI
V [volts]
I [Amps]
f [Hz]
psi/VA
f / fo
Pwr [W]
P / Pmax
150
55
0.9
33
3.03
89%
49.5
2.1%
170
78
2.1
33
1.04
70%
163.8
6.8%
190
112
4.1
33
0.41
56%
459.2
19.1%

PSI
V [volts]
no load
fo (Hz)
V / f

150
85
“0”
37
2.30

170
168
“0”
47
3.57

190
235
“0”
59
3.98

Conclusion not enough Prime Mover source power to generate 2400 VA out at 190 psi. perhaps suboptimal torque conversion 1:1 and needs pulleys. Or better use a field regulated Alternator.

To achieve maximum power transfer MPT, the "impedance" of the air source must match the load. I think this is related to the pressure to flow ratio. If flow is not proportional to pressure then the source impedance is rising with pressure and power transfer drops. I could be wrong about 50% max RPM.

Soul21 · Oct 13, 2023

Thanks. Very helpful. It looks like I have my answer and learned a few more things.

Varying Speed AC Generator to Steady DC

Tony Stewart

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Soul21

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Soul21

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shortbus=

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In-Pipe Turbine Generator (IPTG)

Revolutionary in-pipe generator uses gas flow to power SCADA systems and more at remote locations

Harvesting Pipeline Energy to Produce Electricity

rjenkinsgb

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Tony Stewart

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Soul21

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