MI L-DTL-53133/ 1B
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 requirement 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 voltage transient in amplitudes.
The above requirements shall also apply when the load is suddenly changed from rated load
to no load, except that the initial voltage transient shall involve a voltage rise not to exceed
20 percent of rated voltage.
3.21 Voltage dip for low power factor load. Performance of the set under transient
conditions (as measured by an oscillograph) shall be as follows: With the set operating at
no load and the corresponding voltage and frequency conditions, the output voltage of the
set shall not dip more than 35 percent of the no load voltage when a balanced 3-phase 0.4
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