Scribd
Upload
3K views2 pages

AC Choke Calculation

This document provides instructions for calculating the inductance of AC and DC chokes. It explains that a DC choke has a higher inductance than an AC choke to achieve the same performance reduction in harmonics. Formulas are provided to calculate choke inductance based on mains voltage, frequency, and current. An example calculation is shown for a 55kW motor drive using 400V mains, resulting in an AC choke inductance of 0.21mH and DC choke inductance of 0.44mH. The DC choke rating should consider the rectifier bridge distortion power factor.

Uploaded by

Sri Varshini
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
Available Formats
Download as PDF, TXT or read online on Scribd
3K views2 pages

AC Choke Calculation

This document provides instructions for calculating the inductance of AC and DC chokes. It explains that a DC choke has a higher inductance than an AC choke to achieve the same performance reduction in harmonics. Formulas are provided to calculate choke inductance based on mains voltage, frequency, and current. An example calculation is shown for a 55kW motor drive using 400V mains, resulting in an AC choke inductance of 0.21mH and DC choke inductance of 0.44mH. The DC choke rating should consider the rectifier bridge distortion power factor.

Uploaded by

Sri Varshini
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
Available Formats
Download as PDF, TXT or read online on Scribd
You are on page 1/ 2

Yaskawa Electric Europe GmbH · Hauptstraße 185 · 65760 Eschborn · Germany · Tel.

+49 (0)61 96/569–300

Frequently Asked Question

Topic: How to calculate AC Choke for Mains Supply and Author Yaskawa
DC Choke for DC Bus

Product: All Date 31-Aug-2010

Keywords: Choke, Reactor, DC bus voltage, harmonics Pages 1 of 2


Distribu-
Internal Use only Customer
tion:

I. Generally

An AC reactor and also a DC reactor reduce the harmonics on the current drawn from the
Mains Power Supply.
• An AC reactor has to be connected between mains and input rectifier of the inverter. In
addition to the reduction of harmonics it does help to protect against nuisance tripping
due to voltage spikes, but it causes a voltage drop which reduces available propulsion
power.
• A DC reactor has to be connected between input rectifier and DC Bus capacitors. The
voltage drop is much less than with an AC reactor, but inductance shall be twice as
much to get the same effect to harmonics.

II. Calculation of the Inductance

Generally, a DC reactor has less performance than an AC reactor with same inductance.
Therefore, a DC reactor has to have a bigger inductance than an AC reactor (per phase) to
accomplish the same performance. This does not mean that the total voltage drop in the cir-
cuit is higher with DC choke, in fact it is much less, because the DC reactor is incorporated
into the DC Bus circuit, which provides mainly a DC current to the capacitors, but the DC re-
actor operates only on the overlaid harmonics.
To calculate a choke inductance for given percentage short circuit voltage (vsc%), the follow-
ing formulas can be used:

U Mains
L Mains Choke = vsc% ⋅ 3 ⋅ 2 ⋅ π ⋅ f Mains ⋅ I Inverter Input

U DC average = 1.35 ⋅ U Mains UDC average average value of DC bus voltage


P IDC average average value of DC bus current
I DC average = U DC averageM⋅ η M ⋅ ηinv PM maximum motor power
ηM motor efficiency
U DC average ηinv inverter efficiency
L DC Choke = vsc% ⋅ 2 ⋅ π ⋅ f Mains ⋅ I DC average vsc% percentage short circuit voltage
(E.g.: Use 0.03 for 3% short circuit voltage)

How to calculate AC Choke for Mains Supply and DC Choke for DC Bus.doc
Seite 2 von 2
07.09.2010

Example (HD)
Motor data: PM = 55kW / UM = 400V / IM = 98.5A / ηM = 0.935 / cos φM = 0.86
Inverter data: CIMR-AC4A0139: IInverter Output = 112A(HD) / UMains = 400V
ηinv = 0.96 / Motor Power = 55kW(HD) / IInverter Input = 105A(HD) /
Percentage Short Circuit Voltage (Vsc%): 3%

400 V
L Mains Choke = 0.03 ⋅ 3 ⋅ 2 ⋅ π ⋅ 50 Hz ⋅ 105 A
= 0.21 mH

The inductance of the 3 phase mains reactor is 0.21 mH with a current rating of 105 A.

55000 W
I DC average = = 118 A
1,35 ⋅ 400 V ⋅ 0.9 ⋅ 0.96
400 V ⋅ 1.35
L DC Choke = 0.03 ⋅ 2 ⋅ π ⋅ 50 Hz ⋅ 118 A = 0.437 mH
The inductance of the DC reactor is 0.44 mH.

III. Calculation of the Rated Current for the DC Choke

The (distortion) power factor for a B6 rectifier bridge is 0.955. The rated current of the DC
choke shall consider this value.

118 A
I DC Choke rms = = 124 A
0.955

The rated current of the DC choke is 124 Amps.

How to calculate AC Choke for Mains Supply and DC Choke for DC Bus.doc

You might also like