Our Publications

Our Publications

Here we list our technical publications available for purchase.

Arc resistant design solutions for medium voltage VFD

Most common solutions to achieve arc resistant design of MV VFD.

  • Level of human and hardware protection
  • Response time and possible damages
  • Complexity of the solution
  • Suitability for “special” VFD topologies
  • Maturity of the solution
  • Engineering effort
  • Implications on the system
  • Summary of pros and cons

Purchase price: CHF 24.90

Best practice to avoid EMC issues in drive systems

Electromagnetic compatibility (EMC) is sometimes called the alchemy of electrical engineering due to its complexity. Strict application of fundamental rules and design principles helps to minimize the risk of EMC issues in the drive installation.

  • Compatibility in general
  • VFD design principles to minimize EMC
  • How to select suitable cables an install them properly
  • Best practice for earthing/grounding
  • EMC verification testing

Purchase price: CHF 26.90

Comparison or air-cooled and liquid-cooled VFD

How do the drives compare with regards to the major cooling solutions: air and liquid cooled? The publication presents main benefits and limitations of each solution and provides a compact comparison. Considerations include:

  • Effectiveness of the cooling medium
  • Energy efficiency
  • Heat losses into ambient
  • Overall VFD footprint
  • Design simplicity
  • Enclosure rating
  • Reliability

Purchase price: CHF 15.90

Difference between soft starter and VFD soft starter

What is the key difference between a conventional soft starter and VFD soft starter? How does the motor start differ depending on selected method? We compare factors such as starting current, available starting torque, adjustability of speed ramp, torque oscillations etc.

  • DOL motor start (as reference)
  • Soft start
  • VFD start
  • Comparison

Purchase price: CHF 12.90

Harmonics – A compact guide

A compact document summarizing the most important things you should know about harmonics. The right mix of theory and practically oriented solutions. Explained in understandable way.

  • Harmonic theory (Fourier transform, positive/negative/zero sequence, amplitude law, superposition etc.)
  • Origin of harmonics
  • Effects of harmonics
  • VFD as source of harmonics
  • Spectrum of a 6-pulse diode rectifier
  • Spectrum of multi-pulse rectifiers
  • Theoretical versus real (measured) spectrum
  • Differences between LV and MV drive harmonics
  • Impact of system parameters
  • Modeling of grid impedance
  • Harmonic transfer through DC link
  • Mitigation methods
  • Basics of filter design
  • Passive versus active filter
  • National and international standards and their requirements
  • Network harmonic modeling and studies (principle, tools, practices)

Purchase price: CHF 34.90

Do you prefer webinar format rather than a paper? Click the button below to see our current offering:

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How to understand IEEE 519 standard for harmonic control?

This publication guides you through the IEEE 519 standard, explains key terms and definitions and provides several application examples from VFD perspective.

  • Evolution of IEEE Std. 519
  • Differences between 1992 revision and 2014 revision
  • Point of common coupling
  • Total harmonic distortion (THD) versus total demand distortion (TDD)
  • Maximum demand load current
  • Responsibilities of utility and consumer
  • Voltage distortion limits
  • Current distortion limits
  • Multipliers for higher pulse number
  • Short terms harmonics
  • Application examples

Purchase price: CHF 19.90

LCI versus VSI – A comprehensive comparison

A detailed comparison of the main technologies used in high-power medium voltage variable frequency drives. First each technology is briefly introduced. Then some fundamental technical data is provided. Finally a detailed comparison is given.

The report includes aspects such as:

  • Power scalability
  • Maturity
  • Reliability and availability
  • Grid connection and power quality
  • Inverter duty motor design
  • Motor friendliness
  • Control structures
  • Footprint
  • Commercial side

The comparison focuses not only on the drive itself but the entire drive system.

Purchase price: CHF 26.90

Do you prefer webinar format rather than a paper? Click the button below to see our current offering:

Go to our Webinars

Motor starting: Direct on-line (DOL) versus VFD fed

In this article we describe motor start for direct on-line case and when supplied from a VFD. Get to know the key difference based on straight-forward explanation and illustrations.

  • Direct on-line motor start
  • VFD motor start
  • Performance comparison (starting current, starting torque, power factor, oscillations, thermal behavior etc)
  • Impact on motor design
  • System optimization

Purchase price: CHF 19.90

DC component in VFD transformers: Origin, impact and mitigation

This report focuses on DC component in converter duty transformers. Following topics are addressed:

  • Mechanism of DC component generation
  • Nature of DC component in drive applications
  • VFD topologies that may inject DC component to the grid
  • Severity of DC component for transformer design
  • Effects of DC component on transformer design
  • Mitigation methods and resilience
  • Practical experience

Purchase price: 19.90 CHF

Differential protection of VFD transformers

Differential protection is very common for power transformers. However, in case of multi-winding VFD transformers the implementation does not come without few challenges.

  • Principle of transformer differential protection
  • Implementation challenges for VFD transformers
  • Limitations and drawbacks
  • Conventional vs alternative solutions
  • Practical implementation

Purchase price CHF 19.90

Ratio between grid short-circuit power and VFD installed power

The ratio Ssc_grid/S_VFD is often used as a first screening to evaluate the risk of drive integration into the grid. The article explains the consequences of low ratio, provides a rule of thumb for initial screening and suggests some measures to mitigate the negative impact.

Purchase price CHF 11.90

Short circuit currents in drive systems

Knowing the short circuit current levels in your drive systems is crucial for the design and for the protection. This paper explains the considerations that shall be made.

  • Effects of short circuit current
  • Determination of short circuit current level
  • Short circuit level on the grid side
  • Short circuit level on the machine side
  • VFD contribution to the fault

Purchase price CHF 19.90

Do you prefer webinar format rather than a paper? Click the button below to see our current offering:

Go to our Webinars

Temperature rise test of converter duty transformers

Temperature rise test of converter duty transformers follows the same principles as power transformers. However, the presence of harmonics requires specific adaptation of the procedure.

  • Temperature rise test in general (test setup, limits, standards etc)
  • Test circuit and infrastructure
  • Additional heating due to harmonics
  • Insulating liquid and winding temperature rise
  • Recalculation to nominal conditions
  • Final evaluation and test results

Purchase price: CHF 19.90

Torsional vibration in variable speed drive systems: Origin and mitigation

This article explains the mechanisms of torsional vibration in drive systems and proposes methods for its mitigation.

  • Origin of torsional vibration
  • Effects on the drive system
  • Detection of torsional vibration
  • Mitigation by hardware design
  • Mitigation by control design
  • Verification

Purchase price: CHF 19.90

Transformer winding connection and clock number

VFDs with multi-pulse rectifiers need dedicated multi-winding input transformers. The converter side windings feature phase shifting to enable cancellation of certain harmonic orders and thus reduction of harmonic distortion.

The winding connections are therefore more complex than what power transformers normally have. This paper explains the winding connections / vector groups and the ways how they can be realized.

Purchase price: CHF 19.90

VFD versus fluid coupling – A comparison

This paper presents a detailed comparison of the two variable speed technologies: variable frequency drive (VFD) vs hydrodynamic coupling.

Comparison of “electric VSD” versus “hydraulic VSD” including areas such as

  • Efficiency and input power factor
  • Motor start
  • Performance
  • Space requirements
  • Cooling
  • Lifetime of equipment
  • Voice of customer

Purchase price: CHF 16.90

Do you prefer webinar format rather than a paper? Click the button below to see our current offering:

Go to our Webinars

VFD purchase specification (template)

You can purchase a VFD specification template that we have prepared. It is kept simple and to the point – we have cut the fluff and included real content. As mentioned above, the specification focuses on the performance which is what you really need in the end. It is not written for one vendor or one solution. It does not discriminate.

The document can be used directly or can be integrated into larger specification.

Purchase price: CHF 19.90

VFD soft starter – Essential things to consider

Using VFD as a soft starter requires slightly different design than a drive with continuous rating. Some components can be optimized using the duty cycle. However, there are also few extras to consider.

In this article you will learn some important items that shall not be forgotten when designing a VFD soft starting system.

VFD soft start is technically the best starting method… assuming that the system is designed correctly (not limited to power hardware dimensioning only).

Purchase price: CHF 19.90

What are the transformer guaranteed values?

Transformer datasheet or technical specification contain many parameters. Which of them are constitute guaranteed values? What tolerances apply to those guaranteed values? And what are the peculiarities in case of multi-winding phase shifting transformers?

Purchase price: CHF 15.90 

What is transformer K-factor?

UL 1562 introduces so called “K-factor” to address harmonic loading of transformers. The K-factor is often a source of confusion:

  • There are other “K-factors” with different meaning
  • UL K-factor is not the same as overrating factor
  • UL K-factor was introduced for distribution transformers. Application to converter transformers requires some care to avoid overdimensioning.

Purchase price: CHF 17.90

Why do VFDs sometimes trip during grid faults?

One of the crucial requirements on VFDs is to have certain level of immunity against grid disturbances and faults. It is often called (fault) ride through capability. The VFD shall bridge the grid faults without tripping.

This paper brings a comprehensive overview of this phenomenon. It covers topics such as types of faults and disturbances, typical fault duration, ride through strategy, hardware and software requirements on the VFD, immunity of driven load, root causes of unsuccessful ride through and more.

Purchase price: CHF 49.90

How to pay

a) Using PayPal: send the money to info@mb-drive-services.com
b) Transfer to our bank account:

  • Bank: PostFinance
  • IBAN: CH52 0900 0000 8980 8108 2
  • BIC: POFICHBEXXX
  • Company:
    • MB Drive Services GmbH
    • Baslerstrasse 3
    • 5200 Brugg, AG
    • Switzerland

If you are interested in any of our publications contact us at

  • info@mb-drive-services.com

or use the contact form below.