Motor alternator set EE776

HiTRANS MA Set Load Testing Process - Houghton InternationalCase Study: UK train operator
MA Set: EE776

Reported fault
“Lights pulsing”
Voltage output fluctuating between +/- 20 – 40 Volts

Information supplied
The MA Set would run for 45 minutes at 20 Amps load (vehicle traveling from start point to station) then 10 minutes at 10 Amps (vehicle stationary at the station).

The above cycle would be followed at least 5 times per day and then the MA Set would sit in depot overnight running at 10 amps for around 7 hours before starting the same cycle the following day.

To determine whether any faults were present within the MA Set.

To simulate the MA Sets usual daily working pattern.


  • The MA Set was set up in the HiTRANS™ test bay.
  • Voltage outputs were monitored throughout the 15 hour plus testing cycle.
  • To determine any pulsing, a light was also set up, connected to the MA Set.
  • The entire testing cycle was filmed.

The test results indicated a maximum voltage fluctuation of 8 volts during each 45 minute run at 20 Amps, this being when the vehicle would be traveling between stations and when the lights pulsing would cause an unpleasant journey for commuters.

At no point during the test run did the light pulse / flicker.

The warmer the MA set became the more steady the voltage outputs became.

During the first test run (prior to the 7 hour break of running at 10 Amps) the voltage fluctuated from 415.5 Volts to 407.2 Volts, a difference of 8.3 Volts when on each 45 minute test, whereas during the second test run the voltage fluctuated from 410.5 Volts to 408.9 Volts, a difference of only 1.6 Volts on each 45 minute run.

During this extended simulation, the light pulsing effect did not manifest itself, furthermore, there were no other faults reported during this simulation run.

The MA Set is returned to the customer as fit for service.