GE P50 Agile P253, Техническое руководство

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P50 Agile P253
11 Commissioning Instructions
P253/EN M/C 11-9
I
eq
=
√
(I
rms
² + (K Coefficient* I
2
²) ----------- (1)
Where
I
rms
: RMS current corresponding to the largest phase current.
I
2
: Negative phase sequence current.
K Coefficient is a constant proportional to the thermal capacity of the motor.
The equivalent motor heating current assuming K = 3 for (1) become:
I
eq
=
√ [4/3 * ( I
inject
)
2
]
= (2 I
inject
/
√3) ----------- (2)
The equation used to calculate the trip time at 100% of thermal state is:
t =
τ
ln ((K²- A²)/ (K²- 1))
Where:
t: Time to trip (in seconds)
τ
: Thermal time constant depending on the current value absorbed by the motor:
•
Overload time constant
τ
= T
1
if IFL < Ieq
≤ 2xIFL
•
Start-up time constant
τ
= T
2
if Ieq> 2xIFL
•
Cooling time constant
τ
= T
r
if interrupting device opened
K: Thermal overload equal to (Irms / k* IFL)
Where:
I
rms
: RMS current corresponding to the largest phase current
IFL: Thermal trip or full load current rating (settable)
k : Settable (1 to 1.5 step 0.01)
A: Initial thermal state (eg. If the initial thermal state is 50% then A =0.5)
The time to a thermal trip becomes:
t =
τ
ln(k
2
/(k
2
–1))
The equation used to calculate the time to the thermal alarm is:
t
alarm
=
τ
ln(k
2
/(k
2
–Thermal Alarm /100))
Thermal Alarm = Alarm Threshold setting in percentage
Since a current of twice the setting IFL is applied, consequently one of the following thermal constants
is used:
•
T
1
(overload time constant) if the interrupting device is closed.
•
T
r
(cooling time constant) if the interrupting device is opened.
Apply a current of twice the setting [ in cell: CONFIGURATION, IFL ] to the relay and make a note of
the time displayed when the timer stops. Check that the operating time recorded by the timer is within
the range (as specified in the
Chapter : Technical Specification ). For all characteristics, allowance
must be made for the test equipment being used.
Example
For IFL= 0.5 A and A phase I
inject
= 2 A, T1 = 5 mins