MI L-DTL-53133/ 10C
3.11 Frequency transient performance. Following a sudden increase or decrease in load
up to and including rated load, the governing system shall reestablish stable engine
operating conditions within 1 second. The maximum transient frequency change above and
below the new steady-state frequency shall be not more than 1.5 percent of rated
frequency.
3.12 Frequency adjustment. By means of the frequency adjust device, it shall be
possible to adjust the frequency, (when the set is operating at any constant load) between
390 and 420 Hz but not below 370 Hz nor above 430 Hz. I t shall not be possible to adjust
frequency to a value which will actuate the overspeed protective device.
3.13 Voltage waveform. The deviation factor for the line-to-line and line-to-neutral
voltage waveform for each voltage connection shall be not more than 5 percent, nor shall
any single voltage harmonic be more than 2 percent. I n addition, there shall be no evident
discontinuities, spikes, or notches in the waveform when viewed on an oscilloscope having a
bandwidth of DC to 1.5 MHz and usable viewing screen of 8 x 10 cm. The oscilloscope gain
shall be adjusted such that one cycle of voltage wave covers approximately the entire
viewing screen.
3.14 Voltage unbalance. With the set operating at rated voltage and frequency and no
load, maximum difference between line-to-line voltages shall be not more than 5 percent of
rated voltage for the 240/ 416-volt connection under the conditions of a single phase, line-
t o-line unity pf-load of 25 percent rated current and no other load on the generator.
3.15 Phase balance voltage. The maximum difference in the three line-to-neutral
voltages shall be not more than 1 percent of the rated line-to-neutral voltage. The
maximum difference between the voltage of the 120-volt windings of any phase shall be not
more than 1 volt.
3.16 Voltage modulation. The voltage modulation of the output voltage for any load up
to and including rated load shall not exceed 1 percent. This requirement shall apply to all
line-to-line and line-to-neutral voltages.
3.17 Voltage regulation. The voltage regulation from no load to rated load and from
rated load to no load shall be not more than 1 percent of the rated voltage for all voltage
connections throughout the voltage ranges specified in 3.22.
3.18 Voltage short-term stability (30 seconds). At every constant load from no load to
rated load, the voltage at the set terminals shall remain within a bandwidth equal to 1
percent of rated voltage.
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