MI L-DTL-53133/ 2B
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.
3.13 Voltage unbalance. Maximum difference between line-to-line voltages shall be
not more than 5 percent of rated voltage for the 120/ 208-volt connection under the
conditions of a single phase, line-to-line unity pf-load of 25 percent rated current and
no other load on the generator.
3.14 Phase balance voltage. With the set operating at rated voltage and frequency
and no load, maximum difference in the three line-to-neutral voltages shall be not more
than 1 percent of the rated line-to-neutral voltage when connected for 120/ 208-volt , 3-
phase, 4 wire. The maximum difference between the voltage of the 120-volt windings
of any phase shall not exceed 1 volt.
3.15 Voltage modulation. The voltage modulation of the output voltage for any load
up to and including rated load shall not exceed 2.5 percent. This requirements shall
apply to all line-to-line and line-to-neutral voltages.
3.16 Voltage regulation. The voltage regulation from no load to rated load and from
rated load to no load shall be not more than 3 percent of the rated voltage for all
voltage connections throughout the voltage ranges specified in 3.22.
3.17 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
2 percent of rated voltage.
3.18 Voltage long-term stability (4 hours). At constant ambient temperature,
constant barometric pressure, constant frequency and any constant load from no load
to rated load, the voltage shall remain within a bandwidth of 4 percent of rated voltage
in a 4-hour operating period.
3.19 Voltage drift. With the set operating at constant load and frequency, a change
in ambient temperature up to 33 C° ( 60 F° ) in an 8-hour period shall not cause the
voltage to change by more than 2 percent, set temperature stabilization being
accomplished at both the initial and final ambient temperature conditions.
3.20 Voltage dip and rise for rated load. Performance of the set under transient
conditions (as measured by a magnetic oscillograph) shall be as follows: With the set
initially operating at rated frequency and rated voltage, and following any sudden
change in load from no load to rated load, the instantaneous terminal voltage shall not
dip more than 20 percent of rated voltage and shall reach stable conditions within 3
seconds. Overshoot or undershoot of the final voltage shall not exceed the initial
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