MTE training
© 2009 MTE Corporation
1
MTE Corporation
Improving the Performance and
Reliability of Power Electronic
Systems
MTE training
© 2009 MTE Corporation
2
MTE solutions to Long lead dive
applications
Protection of motors drive cables and Variable
frequency inverters
MTE training
© 2009 MTE Corporation
3
The opportunity
• IGBT devices are used in all modern switching inverter
drives.
• These devices are pushed to operate at higher operating
speeds to increase drive efficiency.
• Problems occur when higher switching speed and motor
lead length are combined causing a dv/dt resonance that
produces standing waves 4 X the bus voltage.
• Copper and wire cost are increasing consider protection
of both the motor and cable as well.
• Not all motors are inverter drive compatible these motors
need sine wave protection.
• It might be cheaper to buy a filter than to replace the
motor and suffer down time.
MTE training
© 2009 MTE Corporation
4
System diagram
MTE training
© 2009 MTE Corporation
5
Motor cable
The motor cable is really a complex transmission line
made up of resistance inductance and capacitance.
As the length increases so does the complexity it adds
to the motor drive system.
MTE training
© 2009 MTE Corporation
6
Inconsistencies in
cable
MTE training
© 2009 MTE Corporation
7
The complex motor
winding
MTE training
© 2009 MTE Corporation
8
Drive output vs voltage
at the motor
Voltage
At the
motor
Voltage
from the
VFD
MTE training
© 2009 MTE Corporation
9
Distance and rise time create
over voltage at motor
MTE training
© 2009 MTE Corporation
10
Drive rated motor breakdown
NEMA MG1 part 31
MTE training
© 2009 MTE Corporation
11
Switching related problems
MTE training
© 2009 MTE Corporation
12
More switching problems
MTE training
© 2009 MTE Corporation
13
Corona Discharge
• Physics explains: between current carrying conductors a
electric field is established.
• Corona forms when voltage potential in wires reaches the
inception voltage (CIV) which is a function of spacing,
insulation type, surfaces, environmental conditions.
• If field strength is high enough air will breakdown or
become ionized by the corona.
• Air ionizes if energy is high enough to change (02) into
ozone (03).
• Highly reactive ozone working with oxygen breaks down
and deteriorates wire insulation compounds
• Long term and short term effects can be catastrophic!
MTE training
© 2009 MTE Corporation
14
Switching an inductor Results in
high energy arcing
MTE training
© 2009 MTE Corporation
15
First turn arc
MTE training
© 2009 MTE Corporation
16
Cable failure
MTE training
© 2009 MTE Corporation
17
Drive Manufactures suggest
• Minimize distance to motor
• Use inverter duty motors MG-1 section 31.4 with
1600 volt rating beyond 150 feet
• Use application specific drive motor cables
• Set switching frequency as low as possible
without causing audible noise problems
• Use 3 phase reactor for 100 foot
• Use advanced filtering 300 to 1000 foot
• “Call MTE”
MTE training
© 2009 MTE Corporation
18
STANDARD MTE output
protection products
• AC Line / Load Reactors
(Single element filter)
• Series A dv/dt Filters
(High order LRC filter)
• Series A 2-8 Khz Sine Wave filters
(High order LRC filter)
• LC 5Khz sine wave filters
(dual element L & C)
MTE training
© 2009 MTE Corporation
19
Standard “RL”
Line/Load Reactors
1 – 2100 Amps
MTE training
© 2009 MTE Corporation
20
RL protection summary
• Low cost motor protection device
• Low cost long lead dv/dt filter up to 300ft
• MTE reactors can be used in both line and load
applications the same one.
• Load reactors extend motor life (heat reduced)
• Load reactors decrease motor noise
• Helps protect motor cables as well
• Protects the drive by allowing the short circuit
protection to work
MTE training
© 2009 MTE Corporation
21
Reactor performance
Motor terminal voltage at 300 feet 2 kHz switching
MTE training
© 2009 MTE Corporation
22
Standard DV/DT Filters
3 – 600 Amps
MTE training
© 2009 MTE Corporation
23
Highlights of series A
dv/dt filters
• 1000 foot guarantee motor voltage will not
exceed 1.5 X supply bus voltage
• Operates 900Hz-8 kHz switch frequency.
• dc to 90 Hz drive fundamental
• Good operational results at 3000 feet.
• Reduces some motor noise
• Reduces some motor heating.
• NOT recommended multi motor applications
MTE training
© 2009 MTE Corporation
24
Series A dv/dt performance
22 Amp dV/dt Overall Performance 30hp 480 Vac Motor
1.80
Peak Voltage at Motor in K volts
1.60
1.40
1.20
Unfiltered
1.00
W ith dv/dt
1.5 x Bus
0.80
Drive Bus
0.60
0.40
0.20
0.00
100 FT
500 FT
1000 FT
Cable Length
MTE training
© 2009 MTE Corporation
25
dv/dt visible performance 1000 foot
shielded cable at 8kHz switching
MTE training
© 2009 MTE Corporation
26
Large dv/dt filter
MTE training
© 2009 MTE Corporation
27
Series A Sine Wave Filters
3 – 1200 Amps
MTE training
© 2009 MTE Corporation
28
Highlights of the series A
sine wave filter
• Provide a 5% THVD sine-wave output voltage.
• Protect non drive rated motors.
• Ensure motor cable voltage doesn't exceed
900volts
• 2-8 KHz switching frequency range.
• Reduce electro-magnetic interference (EMI/RFI)
• Eliminate all the high dV/dT from long-lead runs
• Long lead protection 15,000 feet.
• Eliminate motor audible noise and heat attributed
to PWM inverter drives.
• Step up transformers not required to be “K” rated
• Use one filter for many motors.
• Don’t oversize filter to drive.
MTE training
© 2009 MTE Corporation
29
Series A sine wave
performance
MTE training
© 2009 MTE Corporation
30
Custom Engineered Sine Wave
Filters
Feeding Motors and
Transformers in open
Panel, NEMA 1, 2, & 3R
configurations up to
1500 amps
MTE training
© 2009 MTE Corporation
31
5 kHz LC sine wave filter
• Classic dual element filter sine wave filter
• Inverter frequency not set below 5 KHz.
• Convert a PWM inverter output wave form into a
10% THVD sinusoidal wave form.
• Not recommended for new applications
• Restricted to 480 volts & >5kHz switching.
MTE training
© 2009 MTE Corporation
32
5 kHz sine filter
MTE training
© 2009 MTE Corporation
33
MTE training
© 2009 MTE Corporation
34