Emerson SP2404 - Component Sizing; MCB Sizing for Switching Frequency Filters

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Unidrive SP Regen Installation Guide 203
Issue Number: 2 www.controltechniques.com
11 Component sizing
11.1 Sizing of MCB for switching
frequency filter
The current rating of the MCB must be calculated; taking into account
the switching frequency filter inductance and capacitance, the initial
charging current and the AC supply voltage. Switching frequency filter
inductance and capacitance values can be found in section 3.10 Regen
components on page 25.
L = 2 x L
f
L
f
= Switching frequency filter inductance
C = 3C
f
/ 2 C
f
= Switching frequency filter capacitance
V
c
= V
LL
peak V
c
= Charging voltage
Z
c
= Z
c
= Charging impedance
T
c
= T
c
= Charging time
I
c
= V
c
/ Z
c
I
c
= Charging current
Example:
SP5402 (Heavy Duty) Regen
Switching frequency filter Inductance 190µH
Switching frequency filter Capacitance 77µF
Supply Voltage 480v + 10%
L = 2 x 190µH = 380µH
C = 3 x 48µF / 2 = 96µF
V
c
= 480 + 10% x √2 = 747V pk
Z
c
= = 1.98Ω
T
c
= = 600µs
I
c
= 747 / 1.98 = 377A
The MCB should be rated to the peak charging current of 377A for
600µs, with an rms current of 35A. A suitable MCB should have the
following ratings and features:
Voltage rating: 480 + 10%
Peak current rating: 377A
rms current rating:35A
3 pole with auxiliary (for enable)
The rms current rating specified is taken from the rated continuous
current for the selected switching frequency filter capacitor data sheet.
The MCB is sized both for the system current and voltage, and must also
take into account the cable size from the capacitor branch circuit to the
main circuit.
Table 11-1 DC bus capacitance and inductance values
L
C
----
π LC
380µH
96µF
------------------
π
380µH96µF×
NOTE
Voltage Model
Total DC bus
capacitance
µF
Total DC bus
inductance
mH
200V
SP1201 SP1202 940
SP1203 SP1204 1640
SP2201 SP2202 SP2203 2820 1.4
SP3201 SP3202 5400 0.7
SP4201 SP4202 SP4203 4400 0.211
SP5201 SP5202 3300 0.150
SPMD1201 4400
SPMD1202 5500
SPMD1203 SPMD1204 6600
400V
SP1401 SP1402 SP1403 235
SP1404 410
SP1405 SP1406 410 1.25
SP2401 SP2402 SP2403 SP2404 705 1.4
SP3401 SP3402 SP3403 1350 0.7
SP4401 1100 0.85
SP4402 SP4403 2200 0.423
SP5401 SP5402 3300 0.150
SP6401 4400 L1, L2, L3 0.054
SP6402 SPMA1402 5500 L1, L2, L3 0.054
SPMA1401 4400 L1, L2, L3 0.054
SPMD1401 4400
SPMD1402 5500
SPMD1403 SPMD1404 6600
575V
SP3501 SP3502 SP3503 SP3504
1000 4
SP3505 SP3506 SP3507
690V
SP4601 SP4602 SP4603
733 1.27
SP4604 SP4605 SP4606
SP5601 SP5602 1467 0.470
SP6601 SP6602
2200 L1, L2, L3 0.313
SPMA1601 SPMA1602
SPMD1601 SPMD1602 2200
SPMD1603 SPMD1604 2933