​Reasons for No Indication of Diesel Generator Frequency Meter

1. Fault phenomenon

The frequency meter of a Cummins 40kW diesel generator set is damaged, and a new frequency meter is replaced. When the diesel engine speed reaches 1500r/min, the generator voltage reaches 380V, but the newly installed frequency meter does not display it.

2. Fault analysis:

The newly assembled frequency meter has no frequency display, and this fault is usually caused by incorrect wiring of the assembled frequency meter. Some frequency meters of the same model are equipped with internal transformers, while others are not equipped with internal transformers; The wiring methods are also different, some must be connected to a 380V power supply, while others can be connected to a 220V voltage.

3. Fault cause:

(1) The new frequency meter itself is damaged;

Mechanical indicating ammeter for measuring the frequency of 40kw Cummins diesel generator. There are many types of frequency meters, including electric type, ferromagnetic electric type, and rectifier type converter type frequency meters. Most of the installed frequency meters used for monitoring frequency on the production site use measuring mechanisms of ferromagnetic electric meters.

(2) Incorrect wiring.

4. Troubleshooting method:

(1) Start the diesel engine to the rated speed first, and after the generator generates electricity, measure the AC voltage between the two terminals of the frequency meter using the AC voltage range (500V) of a multimeter. It was found that it is 220V. However, the newly assembled frequency meter (with a built-in transformer and a usage range of 380V) has a different structure from the damaged frequency meter (without a built-in transformer and a usage range of 220V), so the fault is due to incorrect wiring. When using the new frequency meter, The transformer inside the original control box must be disconnected and connected to two different live wires in order to display the frequency of the generator;

(2) Two different live wires were led from the transfer switch and connected to the two terminals of the frequency meter. After assembly and testing, it was found that the frequency was 50Hz when the generator voltage was 380V.

This issue indicates that when replacing the frequency meter, it is necessary to observe the range of use of the frequency meter. Some may have the same shape and model, but the scope of application is different.

5. Conclusion

The various instruments on the distribution board are one of the guarantees for real-time monitoring of the normal operation of the current network, and also one of the specific functions of the distribution board. In particular, the values of ammeters and voltmeter must be presented accurately and quickly, which is related to whether the whole power network has some potential safety hazards that may cause fire, or whether the power network can play its due efficiency.

Therefore, in actual electrician work, strict control should be exercised over the connection of various instruments, especially for some relatively low-level errors, such as problems with series and parallel connections, and instruments not installed according to voltage ratios. Efforts should be made to achieve zero occurrence. For some instruments with abnormal numerical values, detailed inspections should be carried out. Once problems are found with the instruments themselves, they should be replaced immediately, and for instruments that are damaged, they should not be left unchecked, Quick replacement is necessary to ensure that the entire power network is under efficient supervision at all times, and any abnormal data can be promptly handled.