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Product Range Standards and Certifications Quality systems Insulation systems Examples of electric motors repaired Brand names of motors repaired Testing Standard Tests Special Tests Engineering

Product Range:

The types of medium voltage electric motors that M&C repair and manufacture are listed.

Repair of medium voltage electric motor and alternators.
Specialized manufacture of electric motor components, replacement parts and special machines.
Electric motor design changes and improvements, efficiency upgrades, power upgrades, speed changes, and other specialized electrical and mechanical design projects.
250 kW to 36 000 kW
AC motors and alternators
> 1000 V to 13800 V
Induction cage
Slip ring induction
Synchronous
Safe zone, Zone 1 and Zone 2.
Certification & Re-Certification to local and international standards.

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Standards and Certification:

Marthinusen and Coutts holds repairs medium and high voltage motors according to SANS 60034 (and SABS IEC) as well as other customer specific repair specifications (for instance Anglo American’s (AngloGold Ashanti, Anglo Coal, Anglo Platinum, Anglo Base Metals and De Beers) AAC 538/03 and 538/11, Sasol’s SP46, Eskom’s GSS 0389, Arcelor Mittal’s 40-ES-SPEC-01, PPC’s electric motor specification and many other specifications.) Marthinusen and Coutts holds permits to manufacture and repair electric motors and electric enclosures according to SANS 60079-0, SANS 60079-1 (and SABS IEC) (Flame proof, EX d, Zone 1) as well as SANS 60079-0 and SANS 60079-15 (and SABS IEC) (Spark proof, EX n, Zone 2).

We also conduct type testing and specification certifications for major local and international manufacturers of electric motors, for instance Alstom, Zest Electric (WEG Electric motors), WEM, and others.

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Quality Systems:

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Insulation Systems:

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Examples or Motors Repaired:

Over the years, M&C has repaired thousands of motors and transformers for various South African, African as well as International mines, power stations, steel mills, sugar mills, paper and pulp factories, smelters and other industrial users.

Hereunder are but a few examples of the AC, DC, Traction and transformer work we've done. The pictures are not only of completed units, but also show some of the processes involved, to give the reader a glimpse into our proud workmanship.

1	3160 kW, 6600V, 18 pole, Vertical down, (V1), Mitsubishi AC induction motor for a South African Petro Chemical Plant
	To date, M&C has rewound 4 of these motors using a Class F Resin Rich insulation system.
	The photo shows the new resin rich coils manufactured in M&C's advanced coil division.	As the stator are being wound groups of coils are interturn tested as well as pressure tested at 14 kV.
	The winding of the stator is almost complete. Here the connection end is shown.	The non-connection end of the stator is shown, fully wound. The stator winding has been blocked and the end winding support applied.
	The completed motor is tested in the M&C large machines test bay at full voltage, i.e. 11000 V.

2	2500 hp, 6600V, 8 pole, Metropolitan Vickers, AC induction motor
	Marthinusen and Coutts are leaders in the industry and especially on these traditional design hairpin windings. This stator winding is insulated using a hybrid class F insulation system, consisting of a pre-cured sold slot portion and a full class H insulation based VPI system utilizing the M&C EpoVolt HV epoxy-base VPI resin.
	The non-connection end of this "hair pin" winding. We are extremely proud that we can confidently claim that the M&C hairpin windings are better than the original OEM windings.	The reason why these hair pin windings are no longer common in standard AC motors is because of the large labor component required to do all the connection end brazing joints, as can be see from this picture.
	The winding is ready for blocking and overhang support.	It is a very time consuming process to make the series connections on the overhang of this hair pin winding,
	A team of highly skilled and experienced artisans work carefully to make the series connections. One of our most experienced armature winders (Taurus shown on the left) is assisting and mentoring the next generation of armature winders. M&C knows that our industry and business is reliant on such mentorship in order to ensure that the more than 50 years of experience in the repair of MV motors is passed on from one generation to the next.	After connections have been braised, the HV insulation is allied to the overhang. This class H insulation system will provide the motor with a far superior insulation system when compared to the OEM winding and will greatly reduce the risk of stator winding failure in the future.
	A critical aspec of the insulation is the mechanical bracing on the overhang. With the vast experience M&C has gained from mroe than 50 years in the electric motor rewinding industry as well as the fact that we train and employ some of the best armature winders in the motor rewinding industry ensures that this ciritcal aspect is not neglected in the repair of AC motors.

4	3000 kW, 6600V, 12 pole, Synchronous motor for Gold Mine in Ghana
	The starting cage of this Synchronous motor failed. Although many armature winding companies would merely replace the starting cage bars with copper bars, M&C has years of experience in these types repairs. We knew that we had to analyze the bars and not assume their composition. Chemical analysis showed that the bars were in fact not copper, but a special low conductivity allow. We had these special alloys bars (with an electrical conductivity of only 9%) specially manufactured and imported from Europe. These special allow bars is critical in order to achieve the required starting torque. With the failure of the starting cage, the synchronization circuit also failed and had to be replaced. This motor is a mill motor for a leading Gold Mine in Ghana and critical to the production process. M&C knew that production could not be compromised due to a cheap "guess" repair. We thus took every precaution to ensure that the motor relinquishment was of the highest possible standard and quality.
	The starting cage had failed. M&C removed some of the old rotor bars as well as a section from the short circuit cage at conducted chemical analysis on them in order to identify the exact material used since we know that matching these parameters will be critical for the correct starting of the motor, i.e. in order to achieve enough starting torque and a reduced starting current.	We correctly specified these special allow starting cage bars and had them manufactured and imported from Europe.
	The completed rotor is shown here inside the stator winding.	The synchronization circuit was also replaced.
	The completed 3000 kW, 12 pole, 6.6kV, Synchronous motor.

6	3730 kW (5000 hp), 2000V, 16 pole, slip ring induction motor for Placerdome, South Deep Shaft
	This motor is critical for the operation of this mine. When the motor failed, the mine knew that they had to contact the repairer with the reputation of being the fastest in the industry: Marthinusen and Coutts. The M&C engineering services division with our skilled site technicians assisted with the fault finding on site as well as with the disconnecting and removal of this ac electric motor. This electric motor was transported to M&C to do a breakdown rewind, using M&C's proven full class F insulation system, based on the resin rich system.
	Because of the motor, it cannot be transported to the installation location in one piece. This General Electric motor is huge and the stator frame is split into two halves. This is another reason why a global VPI insulation system would not be practical. With the M&C coil manufacturing team's experience and the skills of our armature winders this requirement for a Resin Rich MV insulation system did not pose any difficulty.	The new Resin Rich coils are inserted into the stator core.
	Our skilled armature winders insert the coils. This pictures gives perspective on the shear size of this motor.	After the winding of the stator frame has been completed, the connections are braized and taped to complete the class F insulation system. (Remembering that this is one of the four specialised insulation systems M&C use, being a Resin Rich insulation system.
	Because of the size of the ac motor, it has to be turned on it's side in order to join the connections.	Here we can clearly see teh section of the core where the stator coils are inserted, but now wedged. The reason for this is: This winder motor is so large that it cannot be transported down into the gold mine in one piece. The stator frame is thus split into to halves. The fully wound stator will be tested in out high voltage test bay. The coils over the halving joints of the stator frame will then be remvoed. M&C's field service technicians will then wind these stator coils on site and conduct all the necessary testing to ensure the integraty of insulation system.

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Brand Names of Motors Repaired:

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Testing:

Our distributed reporting structure ensures that the testing department reports to the Engineering section and not to production. This is vital in ensuring that the highest possible engineering and testing standards are maintained throughout the repair and manufacturing process.

Our test capabilities are structured around sound engineering principles. This culminates in many non-standard advanced tests being performed on a regular basis in order to ensure full compliance with local and international as well as customer specific standards.

Standard tests includes:

• Winding Resistance.
  • Tests measurement are taken using high accuracy four wire, high capacity resistance bridges.
• Insulation Resistance and Polarization Index.
  • Measured on high accuracy, high capacity test equipment.
  • This equipment not only measures the insulation resistance value, but also displays the actual test voltage.
  • This is critical since low capacity measurement equipment will give incorrect reasons on larger windings.
• Surge Testing using state of the art Risatti, Baker, P&J as well as Schelgh test equipment.
  • This ensures that any possible inter-turn or inter-phase shorts are detected prior to VPI or on final test.
  • Insulation Resistance in ineffective to detect impending inter-turn and inter-phase shorts.
• No load testing at rated frequency.
  • Values that can be recorded and trended are:
    • Electrical input power (all three phases individually).
    • Power factor (all three phases individually).
    • Voltage (all three phases individually).
    • Current (all three phases individually).
    • Rotational speed.
    • Temperature of windings.
    • Temperature of bearings.
    • Temperature of casing or frame.
    • Temperature of air in and out.
    • Active power (all three phases individually).
    • Reactive power (all three phases individually).
    • Reactive power (all three phases individually).
• Locked rotor testing (also referred to as short circuit testing).
  • Values that can be recorded and trended are:
    • Electrical input power (all three phases individually).
    • Power factor (all three phases individually).
    • Voltage (all three phases individually).
    • Current (all three phases individually).
    • Rotational speed.
    • Temperature of windings.
    • Temperature of bearings.
    • Temperature of casing or frame.
    • Temperature of air in and out.
    • Active power (all three phases individually).
    • Reactive power (all three phases individually).
    • Locked rotor torque and current at various supply values.
• AC Pressure testing.
  • Also known as the High Voltage Test

• Mechanical Pressure testing of frames.
  • This special test ensure the highest level of safety standards on flame proof motors.
• No load testing at other test frequencies.
  • This allows for specialized test such as over speed testing, critical speed determination, electrical and mechanical noise and vibration separation, etc.
  • Values that can be recorded and trended are:
    • Electrical input power (all three phases individually).
    • Power factor (all three phases individually).
    • Voltage (all three phases individually).
    • Current (all three phases individually).
    • Supply frequency.
    • Rotational speed.
    • Temperature of windings.
    • Temperature of bearings.
    • Temperature of casing or frame.
    • Temperature of air in and out.
    • Active power (all three phases individually).
    • Reactive power (all three phases individually).
    • Reactive power (all three phases individually).
• Full mechanical load testing.
  • Marthinusen and Coutts has the highest full mechanical load testing capability in the armature winding industry.
  • We can full load test up to 2000 kW.
  • These full load tests are not merely "quick" test, but full temperature stabilization can be achieved. Thus will type testing can be performed.
  • Out full load testing facility is frequently used by leading OEMs as well.
  • This type of testing can ensure the correctness of the repair, design modifications and new designs.
  • Values that can be recorded and trended are:
    • Electrical input power (all three phases individually).
    • Efficiency.
      • The efficiency can be calculated/measured at various different load points, including full load as well as various different supply frequencies, supply voltages, etc.
    • Power factor (all three phases individually).
      • The power factor can be measured on all three phases individually and at various different load points, including full load as well as various different supply frequencies, supply voltages, etc.
    • Voltage (all three phases individually).
    • Current (all three phases individually).
    • Supply frequency.
    • Rotational speed (and slip).
    • Temperature of windings.
    • Temperature of bearings.
    • Temperature of casing or frame.
    • Temperature of air in and out.
    • Active power (all three phases individually).
    • Reactive power (all three phases individually).
    • Reactive power (all three phases individually).
• Maximum locked rotor testing.
  • This test is also referred to as maximum short circuit testing or a stall test.
  • This test evaluates the compliance with various local, international and customer specific standard regarding permissible locked rotor times.
  • Values that can be recorded and trended are:
    • Electrical input power (all three phases individually).
    • Power factor (all three phases individually).
    • Voltage (all three phases individually).
    • Current (all three phases individually).
    • Supply frequency.
    • Rotational speed (and slip).
    • Temperature of windings.
    • Temperature of bearings.
    • Temperature of casing or frame.
    • Temperature of air in and out.
    • Active power (all three phases individually).
    • Reactive power (all three phases individually).
    • Reactive power (all three phases individually).
    • Locked rotor torque and current at various supply values.
    • Time.
• Pull-out torque testing.
  • The Pull-out torque test is also referred to as maximum overload testing .
  • This test evaluates the compliance with various local, international and customer specific standard regarding permissible overload or pull-out torque.
  • Values that can be recorded and trended are:
    • Electrical input power (all three phases individually).
    • Power factor (all three phases individually).
    • Voltage (all three phases individually).
    • Current (all three phases individually).
    • Supply frequency.
    • Rotational speed (and slip).
    • Temperature of windings.
    • Temperature of bearings.
    • Temperature of casing or frame.
    • Temperature of air in and out.
    • Active power (all three phases individually).
    • Reactive power (all three phases individually).
    • Reactive power (all three phases individually).
    • Time
• Tan Delta testing.
  • This test is used on old windings to take a snap-shot of the insulation degradation and also employed on new windings to ensure a high level of insulation system is maintained

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Engineering:

Marthinusen and Coutts employ some of the leading electrical and mechanical design experts in the electric motor repair and manufacture market. These people are key to the development of superior new specialized AC motors in order to improve efficiencies, power factor, quality, reliability and ultimately to reduce the customers Total Cost of Ownership.

These engineering expertise work closely with some of the best production artisans with many years experience in electric motor repair and manufacture. This ensures that every engineering design or modification will be executed to the letter. Such work ethics is critical to the correct repair and manufacture of large AC electric motors. There is no room for any compromise on quality or even the tight tolerances to which we work to. Critical in any engineering design process is the close interaction with the quality, production and testing departments. Through independent inspectors and assessors it is ensured that no compromise is made on the strict repair standard, because on the repair and manufacture of high capital value large AC motors – more so than on small motors, mistakes and compromises can results in huge production losses and injuries.

Marthinusen and Coutts have successfully upgraded the protection of safe motors (IP55) up to non-sparing motors (Zone 2). This service we offer to our customers on a case by case basis.

Our engineering department utilizes the latest 3D CAD design software. This software enables us to soft-prototype, i.e. run mechanical fitting models without manufacturing samples. This greatly reduces research and development costs as well as time-to-market. Furthermore the overall quality of the design models if far superior to conventional 2D based CAD designs.

• Efficiency: Full load, other partial load points as well as no load.
• Power Factor: Full load, other partial load points as well as no load.
• Current: Full load, other partial load points as well as no load.
• Rotational Speed and slip: Full load, other partial load points as well as no load.
• Losses: Full load, other partial load points as well as no load.
• Temperature rise: Full load as well as other partial load points.
• Bearing life.
• Bearing re-greasing interval.
• Current density.
• Flux densities.
• Critical speed.
• Run-up times.
• Starting current.
• Starting torque.
• Pull-out torque.
• Pull-up torque.
• Stall time.
• Number of starts from cold and hot.
• Torque vs. Speed curve.
• Current vs. Speed curve.
• Efficiency and Power Factor vs. Load curve.

Our design capabilities include the design of new motors as well as upgrading, modifying, improving and upgrading of existing design. Improvements include:

• Increase power output ratings.
• Increased Efficiency.
• Increased Power Factor.
• Improved electrical and mechanical design.
• Bearings.
• Optimized cooling.
• Speed.
• Etc.

In addition to the standard electric motor design, we can also assist with special application designs such as:

• Slip ring induction designs (Wound rotor designs).
• Low starting current designs.
• Double cage rotor designs.
• High starting torque designs.
• Etc.

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