Generators

Question 1

What power are your generators?

Answer 1

2 x Zenoro ( John Deere) 6068AFM85, 250kw, 3 phase, 400/230v, 450A, 50hz 4 stroke, 4 cylinder inline

Question 2

How are your generators wired?

Answer 2

Standard 12 wire reconnectable winding, 3-phase brushless,
2/3 pitch windings

Question 3

No excitation off the generators, what would you do?

Answer 3

• Check that the AVR is not in fault
• Check that the alternator and prime mover are not damaged or in fault
• Check that none of the generator trips have happened
• Refer to the manufactures manual, looking at electrical drawings to assist in troubleshooting

Question 4

What are the types of generator excitation?

Answer 4

• Self excitation (static exciter)
• Brushless excitation

Question 5

Manually parallel generators procedure?

Answer 5

• Carryout normal pre start checks
• Start up generator in manual and check
• Check the voltage of the incoming generator to confirm excitation. If not excitation then check AVR
• Check reverse power and overload trips are reset
  Check the incoming machines frequency, this should be slightly higher
• Switch on check synchroniser
• Switch on syncroscope
• Close the breaker when the incoming machine is at 10 to 12 on the syncroscope
• Once load has taken switch off syncroscope
• Balance the load
• Monitor both generator loads, pressures and temps

Question 6

Explain active and reactive power?

Answer 6

True power (kW) is based on the generators ability to share the total load evenly between each other. Meaning each generator will always have 50% of the load. Reactive power (kVAr) is the level of excitation each generator is providing to overcome its power factor.

Question 7

What are the switchboard safeties and how do we test them?

Answer 7

• Circuit breakers can be tested by operating the on and off switch
• Fuses but are a one time uses
• Preferential trips, by increasing the load on the generator
• Reverse power trip can be tested by increasing the load on one generator and decreasing on the other until the generator starts to become a motor
• Overspeed, can be tested by increasing the amount of fuel being delivered to the engine.
• Emergency stop by pushing the button
• Ground fault protection device can be tested by activating the test function on the device

Question 8

What are preferential trips and how would you test them?

Answer 8

Preferential trips are when a generators load is too high, the switchboard will then remove non essential loads such as an A/C compressor, a boiler, pool heaters, jaquizzi heaters, laundry and galley. This is to prevent the vessel from blacking out.

Question 9

Explain how a generator produces electricity?

Answer 9

The prime mover rotates the rotor inside the stator windings. As the rotor spins it creates a magnetic field, which are then cut across the stator winders, inducing voltage.

Question 10

Explain reverse power trip?

Answer 10

Reverse power trip can be tested by increasing the load on one generator and decreasing on the other until the generator starts to become a motor

Question 11

What are some of the generator safety devices?

Answer 11

• Overloading will allow preferential trips to go, stopping the vessel from blacking out
• Shut down alarms for high temperatures and low pressures
• Emergency stop
• Overspeed shut down
• Reverse power