Can a generator safely handle full load amps at different power factors?

  • Thread starter Thread starter Josh111
  • Start date Start date
Join the discussion
Registration is free. Start your own thread to ask a follow-up.
Sign up Log in
4 replies · 3K views
Josh111
Messages
37
Reaction score
0
We have a synchronous, brushless (not permenant magnet) generator with the following ratings:

3 phase brushless alternator
Model TFW-24
Volt 120/208
Frequency 60 Hz.
Phase 3
KW (P) 24
KVA 30
Power Factor (Cos) 0.8
Insulation class B
Protection Type IP21
Rat S1
Standard JB/T3320-1 2000

If a load with a power factor of 0.8 is applied and the nameplate full load current is drawn, The killowatt is 24 and the killovoltamp is 30. (corresponding exactly to nameplate ratings)
(Since KW = I * E *1.73 * PF and KVA = I * E * 1.73)
or in this case: 24Kw = 83 * 208 * 1.73 * 0.8 and
30KVA = 83 * 208 * 1.73


However if a resistive load with a power factor of 1.00 is applied and the nameplate full load current is drawn, The killowatt is 30 and the killovoltamps is also 30. (Killowatt rating is 125% of nameplate rating while current is at nameplate rating.)
Since KW = I * E *1.73 * PF and KVA = I * E * 1.73
or in this case: 30Kw = 83 * 208 * 1.73 * 1.00 and
30Kva = 83 * 208 * 1.73

Can the generator handle nameplate full load amps without overheating in both situations described above regardless of the fact that the nameplate killowatt rating is overreached when a resistive load is applied?

From what I understand a generator's power factor rating is how low the power factor the load can go at full load amps, and although it is uncommon that it is needed, load power factors can be lower but the load amperage will need to be lowered to prevent overheating of the generator stator. This leads me to believe that if the power factor of a load is 1.00 it can run at full load amperage, which as shown in the above calculations is 125% of rated killowatt. Please let me know if this is wrong.
 
Engineering news on Phys.org

Discussion

First, Does this synchronous generator have a permanent magnet rotor, or does the armature have windings and slip rings?
The generator has two ratings. One is the maximum current in the stator windings, which relates to the volt-amp rating. The second is related to the maximum power output, which is related to the maximum mechanical torque that can be applied to the input shaft at synchronous RPM (torque x 2 pi x rpm/60 = watts). I would stick to the 24 KW and the 30 KVA nameplate ratings.
 
Bob S said:
First, Does this synchronous generator have a permanent magnet rotor, or does the armature have windings and slip rings?
The generator has two ratings. One is the maximum current in the stator windings, which relates to the volt-amp rating. The second is related to the maximum power output, which is related to the maximum mechanical torque that can be applied to the input shaft at synchronous RPM (torque x 2 pi x rpm/60 = watts). I would stick to the 24 KW and the 30 KVA nameplate ratings.

The generator is a brushless type (not permanent magnet rotor.)

My question is that at a power factor of 1 should the KVA or KW rating be used? At full load amps the KW is overloaded with a power cfactor of 1 as described earlier.
 
In practice, volt-amps is used to measure apparent power, and watts is used to measure real power.

This is because when you buy power, you are buying real power. It is common practice to measure just voltage and current (RMS values) when simple benchmarking or testing an electrical machine as being able to measure power factor or phase difference requires more complex equipment.