60Hz designed Geno operating at 50Hz
60Hz designed Geno operating at 50Hz
(OP)
Will receive offer for review data of a Generator constructed to operate at 60Hz, 3.600RPM, to be used at 3.000RPM in 50Hz Grid.
What do I have to consider may vary, besides cooling?
Waveform (Harmonics) may change, how much?
Shall it be rewound to counter this, changing auxiliary winding configuration?
May be more a problem than a faster delivery
What do I have to consider may vary, besides cooling?
Waveform (Harmonics) may change, how much?
Shall it be rewound to counter this, changing auxiliary winding configuration?
May be more a problem than a faster delivery






RE: 60Hz designed Geno operating at 50Hz
The output voltage will need to be less and since a generator 'sets' the voltage as compared to a motor taking what is sent to it. The voltage control board will need to address this.
Keith Cress
Flamin Systems, Inc.- http://www.flaminsystems.com
RE: 60Hz designed Geno operating at 50Hz
FAQ237-1224
Keith Cress
Flamin Systems, Inc.- http://www.flaminsystems.com
RE: 60Hz designed Geno operating at 50Hz
Generator output and voltage will be reduced by 20%. As Keith said, AVR to be set for new reduced voltage. No need to change the stator or rotor windings.
If it has brushless exciter (with rotating rectifier), its ac output will have a lower frequency resulting a higher ripple content in the dc output of the rectifier. Whether your AVR can handle it is to be checked.
RE: 60Hz designed Geno operating at 50Hz
The frequency jumper on the Automatic Voltage Regulator must be moved to the 50Hz. position for proper operation of the Under Frequency Roll Off circuit.
You may want to adjust the overspeed protection circuit on the engine.
The unit will produce the same current and the same voltage, hence the same power. You may have a problem with the prime mover as more torque will be required to develop the same power at at the reduced speed.
Cooling is not an issue at 3000 RPM.
These comments are valid for the majority of diesel gensets manufactured in the range of about 5KW up to about 2MW with conventional voltage regulators. There may be exceptions for very small sets.
respectfully
RE: 60Hz designed Geno operating at 50Hz
Keith Cress
Flamin Systems, Inc.- http://www.flaminsystems.com
RE: 60Hz designed Geno operating at 50Hz
Yes power has to be derated in ratio 50/60. Also Voltage has to be derated in same relation or otherwise excitation has to be raised in ratio 60/50 to keep original voltage.
But this would most probably go over limit of the winding rating. Flux will also increase and most probably waveform will suffer, as losses will increase.
RE: 60Hz designed Geno operating at 50Hz
RE: 60Hz designed Geno operating at 50Hz
Keith Cress
Flamin Systems, Inc.- http://www.flaminsystems.com
RE: 60Hz designed Geno operating at 50Hz
I agree, you won't find the ratings on the nameplate.
You have to look at the manufacturers technical info sheet for the set model.
When you order the set, it will be given nameplate with the single set of ratings that you have selected.
The ultimate KVA that a set will produce is determined by two basic factors;
The maximum current that the set may handle safely, and the maximum voltage, limited by insulation and saturation.
The maximum KW is limited by the capability of the prime mover.
The power factor is the ratio of KW/KVA. The prime mover is normally selected so that the power factor will be 80%.
There is normally a lower rating when a set is designated for use at 50HZ.
This is not because of the speed drop as with a motor, but because the normal 60HZ. rating will be at 480 volts, and the 50HZ. rating will be at 400 volts.
Coincidentally the voltage ratio, (480/400=1.2) is the same as the frequency ratio (60/50=1.2), and is the reason for the derating.
Voltage issues. An electric motor is excited by line voltage. An alternator of the size that I am discussing is excited by the exciter, controlled by the voltage regulator. These components have a wide range of adjustability.
These questions may be considered three ways.
1> The ultimate rating of an alternator.
Maximum allowable voltage times maximum allowable current equals KVA.
2> The rating of the alternator when applied to a standard system.
System voltage times maximum allowable current equals KVA.
The allowable rating will change in the ratio of the original or ultimate voltage to the application voltage.
3> The rating of a complete set with a prime mover.
The power of the prime mover determines the maximum KW. that the set may produce. If the torque curve is fairly straight over the range that the speed is changed (3600RPM/3000RPM, 1800RPM/1500RPM) the reduction in speed will result in a reduction in power (KW). This fits nicely with the normal drop in system voltages from the NEMA world to the IEC world.
I didn't mean to write this much, but as I am this far, please let me share with you an experience with generator ratings.
A customer (a movie theatre) had a fixed load and ordered a diesel generator for standby service.
His system was 120/208 volts. As I remember the load was 32 KVA. The supplier sold him a set rated at 32 KVA at 120/240 volts 4 wire delta. The rated current was 77amps. At the utilization voltage of 120/208, this resulted in a KVA rating of 27.7 KVA.
The set supplier was uncooperative and we had to reduce the load.
To make things more confusing, a diesel set manufacturer will rate the same alternator differently for standby service as compared to prime power service.
To compare ratings, look at the following sites;
Note, F G Wilson used to manufacture the Olympian Brand for Caterpilar. Several years ago, Caterpilar bought F G Wilson.
Caterpilar markets both Olympian (F G Wilson) and Marathon branded gensets.
http://www.fgwilson.com/
htt
On the Cat site, go to Latin America for dual 50/60 hz. ratings.
Cummins Power
http:
and click on:
On-Site Power Generation Systems - Full Line PDF icon (1.8MB)
When the set is ordered, the governor, dead-rack adjustment, voltage, Under Frequency Roll Off, motor overspeed protection etc. will be set for the frequency and class of service, (Prime, Standby, or Continous) and the Nameplate will be supplied showing only one frequency.
I haven't mentioned widely variable temp. rise ratings and "Fudge" factors. Both common in set ratings.
Respectfully