POWER ELECTRONICS

Multi-Step VSI vs

GTO CSI

Power Electronics España S.L. © reserves the right to modify the content without prior notice

01 GTO CSI – Current Source Inverter – 6 pulses – with transformer

Font: High-Power Converters and ac Drives. By Bin Wu

LINE UP SIDE INVERTER MOTOR SIDE

Poor input power factor at low loads with SCR

High Input harmonics, input and output filters needed.

CMV is transferred to the transformer winding

Low overall efficiency due to transformer and high switching losses.

Link inductor stores the energy Requires controlled front end that

add extra complexity. High switching losses High power consumption at low

loads. High current stress on output

capacitors Narrow speed range

High motor THDi at low loads or low frequency.

CMV stress on motor winding due to input transformer (x1.5)

Potential torsional resonance between motor & capacitors

Limited starting performance & dynamic response. (Not used for conveyors, cranes, mills, …etc.)

STO

RED

EN

ERG

Y

Power Electronics España S.L. © reserves the right to modify the content without prior notice

02 GTO CSI – Current Source Inverter – 6 pulses – without transformer

Font: High-Power Converters and ac Drives. By Bin Wu

LINE UP SIDE INVERTER MOTOR SIDE

Poor input power factor with SCR front end

Highly potential LC resonances High Input harmonics, input and

output filters needed.

Link inductor stores the energy Requires controlled front end that add

extra complexity. High switching losses High power consumption at low loads. High current stress on output

capacitors Narrow speed range

High motor THDi at low loads or low frequency.

Potential torsional resonance between motor & capacitors

High CMV stress on motor winding, CMC filters and double isolated motor needed. (x2)

Limited starting performance (overload & torque)

Slow dynamic response. (Not used for conveyors, cranes, mills, …etc.)

STO

RED

EN

ERG

Y

Power Electronics España S.L. © reserves the right to modify the content without prior notice

03 VSI – Multi Step PWM modulation with low Voltage IGBt

LINE UP SIDE INVERTER MOTOR SIDE High power factor

>0.9 under any load condition

High efficiency >96% over 20% load.

Low harmonics THDi<5%

No additional line-up costs

DC link Capacitors store the energy

Large unstressed low voltage parts count, but reduced spare parts.

Redundancy option adds parts and decreases MTBF

Low switching losses. Available N+1,2,3

redundancy Regeneration available

with IGBt rectifier

Low motor THD at any load and frequency condition

High break away torque

High overload capacity (150%)

Fast and accurate transient response

Reduced CMV stress on motor winding (x1)

STORED ENERGY

Power Electronics España S.L. © reserves the right to modify the content without prior notice

04 Summary

GTO-CSI VSI- Multi Step PWMEfficiency

Full Power and FrequencyLow Power (50%)

93%86%

96.5%96%

ReliabilityComponents

MTBF

Low, high components count

1.5 years

High, low components count(Low voltage & redundant)

>10 yearsPower Quality

Harmonics

Potential ResonancePower Factor

High for SCR, lower for IGCTs or Multi-pulse systems (12p, 18p)High for LC filters

Low for SCR

Low, at any load condition meets IEEE519

NoHigh, at any load condition

Motor issuesBreak away torqueDynamic responseTHDI/HVFCMV (Common Mode Voltage)

LowLimited by the DC choke / filter

High at low loads, High stress on capacitorsHigh Stress, requires input isolation transformer

or common mode voltage choke

HighFast, no hardware limitations

Low, multi-step topologyNo, isolation transformer and

controlled neutral pointSize

Non integrated transformerInput choke integratedFully integrated

Extra space requiredStandard

-

--

Standard