vfd training 2p3kv

POWER MODULES FOR VFD

VARIABLE FREQUENCY DRIVES

(VFD)

POWER MODULES FOR VFD

Introduction

• Variable Frequency Drives (VFD) are

used for speed control of AC motors

• Load Commutated Inverters ( LCI)

concept used for controlling

Synchronous Motor

POWER MODULES FOR VFD

FEATURES OF LCI

1. Speed control of Synchronous motor

2. Provides smooth speed control

3. Fuse less design

4. Thyristors are used as switching device

POWER MODULES FOR VFD

RATINGS

a. 1.2 kV modules

b. 2.3 kV modules

c. 4.2 kV modules

Generally 1.2 kV modules are used in

210 MW boilers, 2.3 kV for 500 MW

boilers.

POWER MODULES FOR VFD

Configuration:

Source side converter consists of 6 power modules in 3 phase bridge configuration to get DC.

Load side converter consists of 6 power modules in 3 phase bridge configuration to get Variable Frequency Variable Voltage

POWER MODULES FOR VFD

Power module consists of :

a. Thyristors as switching device

b. Heatsinks to dissipate heat generated in device

c. Snubber resistor and capacitor to protect device against overvoltages

d. Sharing resistors for equalising the voltage across series connected thyristors.

e. Pulse transformer to supply gate pulses to thyristor and to provide isolation between control and power circuit.

POWER MODULES FOR VFD

Construction:

1.2 kV module• Two thyristors are used in series.• Snubber provides protection to thyristor against

over voltages.• Reactor limits rate of rise of On state current• HPTF module gives firing pulses to thyristors

and also indicates healthiness of thyristors.

POWER MODULES FOR VFD

POWER MODULES FOR VFD

POWER MODULES FOR VFD

POWER MODULES FOR VFD

POWER MODULES FOR VFD

POWER MODULES FOR VFD

POWER MODULES FOR VFD

POWER MODULES FOR VFD

anode+

cathode-

p1 n1 p2 n2

J1 J2 J3

Ig

Three-terminal thyristor:

POWER MODULES FOR VFD

POWER MODULES FOR VFD

                        Transient V I characteristics of Thyristor

POWER MODULES FOR VFD

Three-terminal thyristor:

0-1: Forward blocking / OFF state J1,J3: forward, J2: reversed biased 2-3: Forward conduction / ON state J1, J2, J3: Forward biased0-4: Reversed biased J1,J3: reverse, J2: forward biased 4-5: Breakdown

OFF

ON

anode+

cathode-

p1 n1 p2 n2

J1 J2 J3

switching (dV/dI=0)

forward break-over voltage

holding voltage

POWER MODULES FOR VFD

POWER MODULES FOR VFD

POWER MODULES FOR VFD

POWER MODULES FOR VFD

POWER MODULES FOR VFD

POWER MODULES FOR VFD

POWER MODULES FOR VFD

POWER MODULES FOR VFD

POWER MODULES FOR VFD

General mounting arrangement

POWER MODULES FOR VFD

POWER MODULES FOR VFD

POWER MODULES FOR VFD

POWER MODULES FOR VFD

POWER MODULES FOR VFD

POWER MODULES FOR VFD

POWER MODULES FOR VFD

Thyristor stack : 1.2 kV

POWER MODULES FOR VFD

POWER MODULES FOR VFD

POWER MODULES FOR VFD

POWER MODULES FOR VFD

HPTF module

POWER MODULES FOR VFD

Construction:

2.3 kV module • Three thyristors are used in series.• Snubber provides protection to thyristor against

over voltages.• HPTK module gives firing pulses and indicates

healthiness of thyristors.• NTDA module indicates healthiness of thyristors• XPTN module gives attenuated voltage for

control

POWER MODULES FOR VFD

POWER MODULE 2.3 kV

POWER MODULES FOR VFD

THYRISTOR STACK 2.3 kV

POWER MODULES FOR VFD

POWER MODULES FOR VFD

POWER MODULES FOR VFD

Snubber : 2.3 kV

POWER MODULES FOR VFD

POWER MODULES FOR VFD

POWER MODULES FOR VFD

HPTK module

POWER MODULES FOR VFD

POWER MODULES FOR VFD

XPTN Module

POWER MODULES FOR VFD

Synchronous Field Exciter module

Features:• Six thyristors in ac controller configuration.• Snubber provides protection to thyristor against

over voltages.• NHVL module gives firing pulses to thyristors

and also indicates thyristor healthiness• Voltage attenuator and current feedback

POWER MODULES FOR VFD

POWER MODULES FOR VFD

POWER MODULES FOR VFD

POWER MODULES FOR VFD

Field Exciter Module

POWER MODULES FOR VFD

POWER MODULES FOR VFD

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