Electric machines – design and production

Subsea motor, Downhole motor, Electric vehicle motor, ROV motor, Special motors, Electric ship/boat motor, permanent magnet motor, renewable energy and permanent magnet generator.

Contact us! Tel 24/7: +47 93 25 08 00

Karsten Moholt has long experience with overhauling, rewinding and production of electric machines.

An electric machine is a converter from electricity to mechanical power (motor), or from mechanical power to electricity (generator), or from one electric power to another (transformer).

In today’s market there are a lot of standard electric machines, but sometimes it is necessary to make new machines for special applications. Standard machines are made for use in standard environments and are normally made for standard frequency and voltage (50/60 Hz. 230/400/440/690V).

Sometimes it is need for machines working under other conditions, or at different frequency and/or voltage. Karsten Moholt has the knowledge of how to design specially for your needs.

As an example, a standard motor made for 50 Hz, can be speed controlled with a frequency inverter, but when the frequency is increased over 50Hz, the torque will be reduced. Karsten Moholt can design and produce motor running at full torque all the way up to maximum frequency.

What we make
Karsten Moholt offer design and production of electric machines for use under water (subsea motors down to 6000m depth) and into oil well, or other places where it will be necessary to make special design for environments with high pressure, high temperature etc.

Motor power solutions
For control of motors, we can offer complete solution for direct start, soft start or for frequency inverter-controlled motors, direct connected at low voltage machines up to 690 VAC or in combination with transformer and necessary filter for use at higher voltage. Typical up to 4,2 kV AC.

Typical power/size/speed for the most common motors: (Induction motors for subsea)
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This is the standard size, but all motors can be made with other dimension if required.
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Permanent magnet machines
For some application where high torque is required, we can provide a solution utilizing a permanent magnet motor. By doing this we can create motors with high torque which are connected directly to the load without the aid of a gearbox. We can also produce permanent magnet motor solutions to meet high efficiency and/or low weight requirement scenarios.

KM do all design and calculation for these motors. Magnets are custom made, to make an optimal motor for right temperature and performance. Normally we use Neodymium-IronBoron (NdFeB) magnets, the most powerful and advanced commercialized permanent magnets today.

This is the standard size, but all motors can be made with other dimension if required.

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They can be made with different quality depending on temperature and energy product (BH).

For high temperature (up to 350 ºC) motor we use Samarium Cobalt (SmCo) magnets. The advantages are superior resistance to high temperature. Excellent resistance to corrosion, no coating is needs for surface protecting. High working temperature. SmCo is suitable for machines with high magnetic requirements and good for strict working environment requirement. They are more expensive and about 90% of the energy product (BH) compared to NdFeB.

Permanent magnet module motors
Karsten Moholt is working with a module-based series of permanent magnet motors.

The idea by this concept is to be able to make a flexible motor-concept, where it is possible to add modules to reach the needed torque. Each module length is as standard, 50mm.

The diameter of the stator core is four dimensions. D65mm(1Nm/module), D95mm(2,5Nm/module), D120mm (14Nm/module) and D170mm (42Nm/module). Custom sizes can be created on demand.

The Nm/module value is just an indication. It might change depending on environment temperature, speed/frequency, operating time etc. As an example, if the application needs 7 Nm, it can be 7 modules of D65mm (total 350mm-length) or 3 modules of D95mm (150mm-length).

To find the total length of the motor, the stator end-winding and the bearing house must be added.

The output power for the motor will depend on the motor rpm. and can be calculated by use of this formula:
induction motors4 imgWhere P is the power in W and M is the torque in Nm.

Typical size for D95mm motor with one and three modules, will be approximately like this:

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These motors are made with a bigger distance between the rotor and the stator than standard motors. We do this to be able to install a barrier inside the stator to prevent pollution from the rotating parts to damage the winding. For use under water these motors will be compensated with oil for pressure compensation, lubrication and cooling.

By use of this barrier, the pollution from IPM-motor KM-PM-D450-L250 SPM-motor KM-D95-8p-9s-1 module KM-D95-8p-9s-3 module the rotating part or water ingress will not affect the winding, and even if the motor is filled with water, the winding will not be destroyed.

Our motors can be delivered with rotation feedback built in. Sometimes it is only needed to have feedback for the motor rpm, feedback for running the motor in Close loop, or if position is important for robotic operation, we can customize this based upon your requirements.

For use in subsea applications, we have solutions that work reliable under high pressure and operating in oil.

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Power cable/connectors
Depending on the environments, it might be necessary to use special cable solutions. We can help to find an optimal solution by cooperating with cable manufacturers or find standard cables that can be used.

We can also deliver different solution for connection of the motor by use of connectors or by direct connection.

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Hydraulic Pumps (HPU)
Our motors can be designed for interface to customers pump, or we can deliver a complete solution with motor and pump. For shaft interface, we prefer spline shaft, but can also deliver motor shaft with wedge. For need of hydraulic pump, we can cooperate with specialists that can deliver optimal pumps and valve solutions. Normally the motor can be filled with the same oil as the hydraulic oil used in the hydraulic pump and this will be easy to combine. No need for mechanical seal.

We can also deliver solution with centrifugal pumps, piston pump, screw pump, or other pump solutions. Examples of combination of KM-motors and Hawe hydraulic pump. Please contact us for other configurations.

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Monitoring and analysis
All our motors and generators can be delivered with monitoring and analysis solutions. Examples of parameters that can be monitored are temperature, vibration, mechanical speed, motor voltage (When use of long cables!) and water in oil sensors for oil filled motors.

For motors used with long cable/under water, motors can be delivered with integrated motor monitoring PCBs for use with CAN-Bus, Ethernet or RS485.

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Hydraulic compensators
For machines made for use under water. The machine will be filled with oil for cooling and for compensating for the pressure. We can help specified size and/or deliver compensators which are suitable for the actual design.

If you require an extra barrier we can advise/design an optimal solution for your requirements.

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Centrifugal pump
Our motors can be designed to run at optimal speed for use on centrifugal pump. Normally standard motors are made for 50/60Hz, but our motors can be delivered for frequency up to 200Hz as a standard. However, we can produce higher frequency on request.

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Mechanical seals
For shaft running in other medium than the medium inside the motor, it is sometimes necessary to use mechanical seals. Our motors can be custom developed to your medium and pressure requirements.

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Gear box
If you need a gearbox to accompany your motor, we can offer an interface to match your gearbox, or a gearbox integrated within the motor. We can offer various forms of gear box including planetary gear, angle gear or harmonic gear solution. Other solution can also be delivered if preferred.

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Interface to other components
Our motors are produced according to customer’s needs; this also includes interfaces for equipment that will be assembled to the complete machine. Just let us know your needs, and we will fi nd a good solution. As relevant example we can deliver motors with interface for thrusters, ball screw/roller screw actuator for linear movement.

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