MEDIUM VOLTAGE DRIVES
FOR
INDUSTRY
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1.- INTRODUCTION
For Medium Voltage installations between 3000 V and 13800 V where speed
control of motors is needed the state of the art drives require input
transformers and series connected semiconductors.
The I.E.S. Hyper Drive drive uses new PWM techniques to the Slip Energy
Recovery S.E.R. principle to control the speed of motors below and above
synchronous speed without series connection of devices.
This drive utilises the wound rotor motor as a step-down transformer, does not
use series or parallel connected semiconductors and has a full redundancy
using a Liquid Resistor Starter.
2.- DESCRIPTION
The Hyper Drive consists of the following main elements:
§ Wound Rotor Motor
§ D.C. Link filter
§ Liquid Resistor Starter
§ Recovery PWM converter
§ Rotor PWM converter
§ Recovery Transformer
MEDIUM VOLTAGE SUPPLY
M.V. CIRCUIT BREAKER
RECOVERY TRANSFORMER
MOTOR
PWM ROTOR
CONVERTER
DC FILTER
PWM RECOVERY
CONVERTER
LIQUID RESISTANCE
FIG. 1
BLOCK DIAGRAM OF HYPER DRIVE PWM AC DRIVE
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The liquid resistance starts the motor and takes it up to the minimum operating
speed. Simultaneously, the Recovery PWM Converter boosts the D.C. link
voltage to a value higher than the peak voltage of the AC supply from the
Recovery Transformer behaving like a true Active Front Converter with
sinusoidal current generation and current displacement angle control. When
the speed is reached the Rotor Contactor closes, the Liquid Resistance
Contactor opens and the Rotor PWM Converter is enabled. During the transfer
no voltage spikes appear on the motor since the current path is never
interrupted. As the current generated by the rotor converter is the same as that
flowing in the L.R.S. before the transfer, there is no change in speed in the
motor.
The Rotor PWM Converter draws
or injects sinusoidal current from
the motor windings depending on
the speed. The Rotor Converter
calculates the rotor current
frequency as a function of the
motor
speed
and
supply
frequency. It also establishes the
amplitude
of
both
current
components, motor active or
torque producing current and
motor fluxing current thus
enabling motor power factor
control between 0.95 and 1.00.
FIG. 2
TYPICAL ROTOR CURRENT
In summary, the S.E.R. is a 4 Q system with two bi-directional inverters. The
Recovery Converter drains or sources current to maintain a fixed voltage on the
D.C. link. The rotor converter, also drains or sources current from the motor to
control torque and flux.
The Hyper Drive can control the speed of the motor below and above synchronous
speed without torque reduction as is the case with A.C. inverter drives. This means
that a 5000 kW @ 1000 rpm motor operating with the IES drive will deliver 6000 kW
@ 1200 rpm whilst an A.C. drive will only deliver 5000 kW.
The IES drive includes the unique feature of redundancy which offers a “bumpless” transfer to Liquid Starter in the event of a trip or fault in the drive. This is
achieved by positioning the electrodes in the L.R.S. so that the current taken by the
motor at the time of transfer is identical to that flowing in the Rotor Converter before
the trip. As the current is the same, so is the torque, and therefore the speed does
not change. The position of the electrodes is continuously calculated as a function of
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the rotor current and speed. Once the drive has transferred to L.R.S. the motor is
taken to near synchronous speed with the Liquid Starter and the rotor windings
shorted out.
FIG. 3 AN IES DRIVE RATED AT 3,500 kW @ 1000 rpm
3.- FEATURES
1. FEATURES
The main characteristics of the Hyper Drive AC drive are listed below, giving
the main benefits derived from them:
q
Operation at voltages ranging from 3,000V to 13,800V without stepdown transformers.
q
Precise speed regulation (Regulation = 0.01%).
q
Very low current harmonic distortion on the motor and the supply
(THD < 3.5%).
q
Very low pulsating torques on the motor shaft.
q
Motor power factor compensation (System P.F. = 1).
q
Very high drive efficiency (Typically > 99.2%).
q
Reduced inrush current.
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q
Very high starting torque (T > 220%).
q
Very high overload capacity (I > 150% for 90 secs).
q
Redundancy both for operation a nd starting.
q
High reliability due to:
♦ Low component count.
♦ No paralleling of semiconductors.
♦ No series connection of power semiconductors.
♦ High safety margins on voltage in semiconductors (4,500V).
♦ GCT ( Integrated Gate Commutated Thyristor) in hermetic
press-pack housing.
FIG. 4 A GCT RATED AT
4000A / 4500V OF THE
TYPE USED IN IES DRIVES
♦ No electrolytic capacitors used in the power sections.
♦ Simple forced air cooled system with no high efficiency heatsinks.
q
Low dV/dt applied to motor windings (500 < dV/dt < 800 V/µs).
q
Very small foot-print.
q
No air conditioning requirements in switch-rooms.
q
Simple operation.
q
Extensive graphic HMI (Human Machine Interface) for:
♦ Status of drive.
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♦ Diagnostics.
♦ Parameter Graphs.
♦ History Records.
FIG. 5 TYPICAL FORCED
AIR COOLING
INSTALLATION FOR AN IES
DRIVE SHOWING THE
DUCTING OF THE HOT AIR
FROM THE UNIT.
HUMANMACHINE
MACHINEINTERFACE
INTERFACE
2.4.-HUMAN
The HMI has a back-lit LCD 256 x 128 pixels which supports up to 16 x 40 text
characters and graphics.
It has 4 screen addressable soft keys as well as 8 direct access function keys
and an acoustic alarm which triggers whenever an alarm is logged.
q
Easy monitoring of the status of the drive and main switch-gear by animated
graphics.
FIG. 5 DISPLAY SHOWING OPERATION IN L.R.S.
q
FIG. 6 DISPLAY SHOWING OPERATION IN S.E.R.
Monitoring of main operating parameters by displaying analogue
measurements.
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q
Drive “Ready to Start” screen showing the status of all the conditions to be
met prior to a start.
FIG. 7 DISPLAY WITH “READY TO START” SCREEN
FIG. 8 DISPLAY WITH “TEMPERATURE” SCREEN
q
“Alarms” screen showing any alarm that is present for trouble-shooting.
q
“History record” screen showing all the alarms and events with date time
and description.
FIG. 5 DISPLAY WITH “HISTORY RECORD” SCREEN
q
FIG. 5 DISPLAY WITH “HISTORY RECORD” SCREEN
“Analogue Parameter Trends” screens with fast and slow refreshing.
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5.- TECHNICAL SPECIFICATION
ELECTRICAL CHARACTERISTICS
Nominal Power
1,000 ÷ 10,000 kW
Mains Supply Voltage
3 ÷ 13,8 kV
Mains Supply Voltage Tolerance (Steady State)
± 15%
Mains Supply Voltage Tolerance (250 ms)
+ 20% / -30%
Mains Supply Frequency
50 Hz / 60 Hz ± 5%
Nominal Current
Dependant on motor
Standstill Rotor Voltage
Dependant on motor
Overload Capacity
150% 90 s
System Power Factor
Motor P.F. ≈ 0.88
OPTIONAL: Power Factor Compensation
(P.F. = 1 Optional)
Power Factor on the Recovery
P.F. = 1
(Capacitive Optional)
Efficiency
≈ 99.2%
Normal Speed Range
0% ÷ 120%
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OTHER CHARACTERISTICS
Operating Temperature Range
- 10ºC ÷ + 40ºC
Starting Temperature Range
- 10ºC ÷ + 60ºC
Storage Temperature Range
- 25ºC ÷ + 75ºC
Relative Humidity
95% Non condensing
Noise Level
< 80 dB(A)
Cooling
Forced air cooling
Protection Degree
IP 23
Serial Communications
Mod-bus or Profibus
User Programmable Digital Inputs/Outputs
4+4
User Programmable Analogue Inputs/Outputs
2+2
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CONTACT DETAILS:
GEOFF ROPER
MANAGER AUSTRALIASIA
AUSTRAL IASIAN OFFICE
ROSEVILLE 2069
NSW AUSTRALIA
TEL:
FAX:
MOBILE:
+61 2 9440 7700
+61 2 9440 7755
+61 438484178
EMAIL: geof f .roper@ies g.c om.au
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