output load protection2 - MTE Corporation€¦ · • MTE reactors can be used in both line and load applications the same one. • Load reactors extend motor life (heat reduced)

1MTE training© 2009 MTE Corporation


MTE Corporation

Improving the Performance and Reliability of Power Electronic Systems


MTE solutions to Long lead dive applications

Protection of motors drive cables and Variable frequency inverters


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.


System diagram


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.


Inconsistencies in cable


The complex motor winding


Drive output vs voltage at the motor

Voltage At the motor

Voltage from the VFD


Distance and rise time create over voltage at motor


Drive rated motor breakdown NEMA MG1 part 31


Switching related problems


More switching problems


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!


Switching an inductor Results in high energy arcing


First turn arc


Cable failure


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”


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)


Standard “RL” Line/Load Reactors1 – 2100 Amps


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


Reactor performance

Motor terminal voltage at 300 feet 2 kHz switching


Standard DV/DT Filters3 – 600 Amps


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


Series A dv/dt performance

22 Amp dV/dt Overall Performance 30hp 480 Vac Motor

0.00

0.20

0.40

0.60

0.80

1.00

1.20

1.40

1.60

1.80

100 FT 500 FT 1000 FT

Cable Length

Pea

k Vo

ltage

at M

otor

in K

vol

ts

UnfilteredWith dv/dt1.5 x Bus Drive Bus


dv/dt visible performance 1000 foot shielded cable at 8kHz switching


Large dv/dt filter


Series A Sine Wave Filters3 – 1200 Amps


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.


Series A sine wave performance


Custom Engineered Sine Wave Filters

Feeding Motors and Transformers in openPanel, NEMA 1, 2, & 3Rconfigurations up to1500 amps


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.


5 kHz sine filter


Documents

output load protection2 - MTE Corporation€¦ · • MTE reactors can be used in both line and load applications the same one. • Load reactors extend motor life (heat reduced)