Connecting a 60Hz Air conditioning on a 50Hz generator 2

[sparkview]

Hi folks,

A friend of mine got a portable 2.2kVA generator as a gift. However, the household electrical grid is 60Hz 127/220V, and hence most appliances are 60Hz. My friend wants to use the generator as a backup to supply an air condition (inverter type). What can be the consequences of connecting the 60Hz on a 50Hz supply? I know for a fact that the compressor might "run" slower, however, the A/C contains mostly electronic components.

Is there another solution to use the generator either way? Probably with a frequency converter or some form of increasing the engine RPM?
Find attached the generator specs.

Thanks in advance for any help.

Kind regards,

Jairo

 

[waross]

We need some information about the A/C

generator as a backup to supply an air condition (inverter type)

Is the A/C inverter type or is the generator inverter type?
Apart from that, it doesn't look good.
Running a single phase 60 Hz motor on 50 Hz may be problematic.
The starting arrangement may not work properly at 50 Hz. It may work. It depends.
Compressors are generally designed to take advantage of the flywheel effect to carry over the torque peaks of the compression cycle.
It may work on 50 Hz. It depends.
But the big if is capacity.
Rated Amps x rated Volts = Volt Amps, VA. (VA/1000 = KVA)
Using the rated Watts on the A/C may be misleading.
That set will reliably start a 50 Hz motor of 833 VA (0.83 KVA)
There is a grey area where it may start the motor if there is no other load up to about 1000 VA (1 KVA).
These numbers may be off a little with a 60 Hz motor on 50 Hz.
That is pretty small for an A/C unit.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[sparkview]

Yes, only the A/C is inverter type.

 

[waross]

Specs on the A/C?

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[FacEngrPE]

50 Hz supply on a 60Hz motor with a constant torque load - like a compressor will adversely impact motor life, possibly by a significant amount.
If the compressor is variable speed then the question has more to do with the electronics it might work, it might fault, or components might fail, no way to tell with out more info in the A/C.

 

[sparkview]

Bill,

Attached the condensing unit nameplate.

 

[waross]

This doesn't look good.
The gen-set is rated at 2000 KVA at 220 Volts.
That is 9.1 Amp continuous, 10 Amps peak (Starting).
The A/C is rated at 10 Amps continuous, 12.5 Amps starting. additionally there are two fans, the condenser fan and the evaporator fan for an additional 1.69 Amps.
That is a total of 11.69 Amps on a generator rated at 10 Amps continuous.
The gen-set will be unable to start or run the A/C.

Some other considerations.
Inverter drive; The inverter may not care too much about the input frequency.
It is just going to a rectifier bank.
But voltage is a concern.
A motor has both a minimum and a maximum voltage.
If the voltage is too low, the motor will not be able to generate enough torque to drive the load.
If the voltage is too high the magnetic circuit will saturate and the current will increase dramatically with a small further increase in voltage.
This will also happen with a transformer if the supply voltage is too high.
Saturation is frequency dependent as well as voltage dependent.
That brings us to the V/Hz ratio.
As the frequency is dropped, the saturation voltage also drops.
This will not be a factor with the inverter driven compressor but it may be a factor with the control transformer and possibly the fan.
The spec sheet list the maximum allowable voltage as 253 Volts.
With respect to the V/Hz ratio the maximum voltage at 50 Hz will be 253V/60Hz x 50Hz = 211Volts
Do not apply more than 211 Volts at 50 Hz.
You should carefully check both the voltage and the frequency. Going over the V/Hz ratio will lead to a possible quick burn-out of either fan or the control transformer, or both.
Additionally, the fans will run slower at 50 Hz. The unit may function at reduced capacity.
But, all is not lost.
that generator is rated for 380 Volts and 2.2 KVA.
If you run the voltage up somewhere past 300 Volts and step it down to 210 Volts or 208 Volts with an auto-transformer, there is a fair chance that it may work, but at reduced capacity.
Another issue is that the motor may not have enough power to drive the output.
If you believe the manufacturers HP rating on a small gas motor then I may have a bridge for sale.
No guaranties.
You heard it on the internet and this information may be worth exactly as much as you paid for it.


Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[sparkview]

Hi Bill,

Thanks for the great information provided.
Can you provide additional information on the auto-transformer/ bridge you suggested?

If you run the voltage up somewhere past 300 Volts and step it down to 210 Volts or 208 Volts with an auto-transformer, there is a fair chance that it may work, but at reduced capacity.]If you run the voltage up somewhere past 300 Volts and step it down to 210 Volts or 208 Volts with an auto-transformer, there is a fair chance that it may work, but at reduced capacity.

Kind regards,

Jairo

 

[waross]

The auto-transformer is real.
The bridge is a joke.
Small engines such as the one driving your generator are often over rated or rated at unreasonable parameters.
For instance your generator motor is HP rated at 3600 RPM but at 50 Hz will be running at 3000 RPM.
The joke suggests that someone naive enough to believe the HP rating on a small gas engine may be naive enough to fall for a scam and think that he has bought a public bridge.
No disrespect intended.
It is a North American saying that I should not have used on an international forum.

An auto-transformer has the primary winding in series with the secondary winding.
As an example, a 240/120 Volt rated transformer suitable for buck/boost operation will become a360 Volt transformer when the windings are in series.
You may apply 240 Volts across the 240 Volt winding and draw 360 Volts from the combined windings.
You may apply 360 Volts to the combined windings and draw 240 Volts across the 240 Volt winding.
If you dial the generator voltage to 315 Volts you may draw 210 Volts from the 240 Volt winding.
Some transformer manufacturers sites give information on auto-transformer connections.

Dropping the voltage by 1/3 will give a 1.50% increase in the allowable current.

Verify that the AVR can go up over 300 Volts before spending any money.
Another hack is using a small transformer or a resistor voltage divider to fool the AVR.


Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[TugboatEng]

Just to add to what waross has said, when generator sets, the generator set needs to have double the nameplate power of the electric motor it's driving for direct on line motor starts. During the motor start, the drop in generator output voltage can be so much that magnetic contactors can chatter or even drop out completely. If the system is truly inverter based with the ability to ramp the compressor up to speed you don't need as much margin.

I wouldn't call using a transformer to feed an AVR a hack. All of the regulators in my fleet require the use of control transformers if you can't provide the correct voltage.

 

[waross]

According to the A/C nameplate, the starting surge is only 125% rather than the normal 600% of a DOL start.
I called the transformer on the AVR a hack because it will probably be working at non-standard voltages, as will the generator.
Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[LittleInch]

Your unit appears to be one of these??

http://www.sinbestpower.com/product/3467

Seems to be an "Excalibur dragon CX generator.

They are listed as 5-0/60 htz machines s there may be a switch or adjustment in the control panel to make it a 60 htz machine?

I can't find a manual online or even a decent picture of the control panel. Can you get your mate to send you a good picture of the control panel?

Or the manual?

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[TugboatEng]

I guess I'm used to NEMA nameplate ratings and not Harbor Freight ratings.

 

[sparkview]

I can't find a manual online or even a decent picture of the control panel. Can you get your mate to send you a good picture of the control panel?

Or the manual?]

Find below additional information on the generator in question.

Jairo

 

[LittleInch]

Jairo,

What's going on here?

That picture and generator is not the same thing as your original sheet which clearly lists a much smaller generator.

the 5500 appears to mean 5.5 kW but there seems to be even less information about this other than some sites in ecuador!

Rather surprisingly the machine or any other information doesn't say if this is 50 or 60 htz.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[sparkview]

Jairo,

What's going on here?

That picture and generator is not the same thing as your original sheet which clearly lists a much smaller generator.

the 5500 appears to mean 5.5 kW but there seems to be even less information about this other than some sites in ecuador!

Rather surprisingly the machine or any other information doesn't say if this is 50 or 60 htz.]

Not completely sure about the spec sheet either. This is what they provided. I'll take a better look and see if the specs match. Nevertheless, it's a 50HZ producing Genset that they want to use to supplying 60hz equipment.

 

[itsmoked]

The schematic isn't matching the front panel. 220V AND 380V? No sign of that in the schematic. Odd.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[LittleInch]

And 220v at 5.5 KW is nearly 25 Amps.

All the info on these seems to be South American.

I would just start it if it can be started, plug it in, stand back and see what happens....

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.