MPS Permanent Magnet motors
Our submersible PM motors are powerful, reliable and efficient machines. In combination with our PMVSD® they provide unmatched torque, power and speed control for both PCP and ESP applications. Our modern motor design and proprietary motor control methodology provide an operating speed range of 50 to 6000 rpm from one single motor design. This speed range covers both current and future pump technology requirements and provides excellent optimisation flexibility forchallenging PCP and ESP applications that often featurerapidly changing downhole conditions.
The high MPS PM motor efficiency means that the heat rise in the motor is very low compared to any induction motor in any application. The shorter, more robust mechanical design, combined with the lower heat rise of our PM motor provides a significant increase in reliability and hence run life versus an induction motor. A single section MPS PM motor can replace tandem induction motors in most applications, providing a significant increase in reliability and motor efficiency. The short PM motor length also allows PMESP® systems to be safely installed in wells with severe doglegs, where standard induction motors cannot be installed due to their long length and small rotor to stator air gap.
The outstanding thermal characteristics of our PM motors also allow them to be installed in applications where there is minimal cooling flow past the motor. MPS PM motors are currently installed and operating below perforations in both ESP and PCP applications without use of a cooling shroud.
MPS PM motors provide maximum torque from almost zero rpm. Their torque density and torque characteristics allow them to directly drive PC pumps, providing more torque and a wider operating speed range than any gearbox-connected induction motor. By eliminating the gearbox, MPS PM motors significantly improve downhole reliability.
MPS PM motors are currently available in 456 and 562 series.375 and 738 series motors will be available in late Q2 2017. The rated maximum operating temperature of the motors is 400deg.F allowing them to be installed in wells with a maximum bottom-hole temperature of 350deg.F. The mechanical and electrical motor interfaces are industry standard, meaning that they can be combined with most brands of motor seal and motor lead extensions. They are therefore easilyintegrated into existing ESP systems.
Servicing and handling procedures for MPS PM motors are the same as those for induction motors, although operating time at the well site and handling risks are significantly reduced due to the short length of the motor. Because PM motors generate potentially lethal voltages whenever the shaft of the motor is turned, all service personnel that install, pull, or service MPS PM motors must be trained and certified by MPS.
Motor Design
The MPS PM motor has a very advanced and new design compared to motors offered by its competitors. The structure of the rotor and the stator are unique and provide the best in industry motor efficiency, reliability and power rating per unit length. The design is done in-house with extensive modelling and performance simulations using super computers.
One of the key differences is in the material of the permanent magnets used in the rotors of the MPS motors, which is a specially formulated, proprietary, Samarium Cobalt material that is a non-corroding rare earth alloy. The temperature rating of the MPS permanent magnets are over 600 degrees centigrade. This superior design enables the MPS PM Motor to outperform all other submersible PM motors available in the market.
Reliability
The low heat rise in the motor limits the exposure of the internal components of the motor to damaging high temperatures during operation.
The lower operating temperature improves the performance and life of the winding insulation, rotor bearings, pothead connection and the motor oil.
The low heat rise in the motor reduces the volume of oil expansion and hence there is less cycling of the oil in the motor seal / protector, which leads to increased life of the motor seal / protector.
The PM motor does not experience any inrush current during start-up.The motor typically takes 10 to 50% of the rated motor current at the time of start-up.
The elimination of inrush current reduces the stress on the complete electrical system, from the surface transformer to the motor winding. The occurrence of electrical related failures is significantly reduced.
Pothead / MLE failures related to temperature and inrush current are significantly reduced in MPS PM motors.
The large stator to rotor air gap and short length of MPS PM motors means that they are mechanically very reliable. An equivalent induction motor is at least twice as long and incorporates a very small stator to rotor air gap.
Motor Heat Rise
MPS PM Motors have significantly lower heat rise than any induction motor.
The maximum heat generated in an MPS PM motor is at the motor winding that is located close to the housing. This assists in heat transfer from the motor to the well fluid.
The MPS PM rotor runs much cooler than the windings as there is no magnetization current or induction required. The centre of the motor is no longer the hottest part of the working motor.
The friction and stator iron losses are reduced due to the shorter length of the motor and all rotor losses are eliminated due to the unique design of the MPS PM motor rotor.
Factory tests on PM and Induction motors showed the rapid rate of heat rise of an induction motor in comparison to the MPS PM Motor.
Motor Efficiency and Power Cost
MPS’s proprietary motor control methodology ensures that our PMVSD® is always operating our PM motors at their maximum efficiency. On average, MPS PM motors operate at least 10 percentage points higher in efficiency than an equivalent induction motor and normally provide a power saving of 20%. The power saving is much higher in gassy ESP applications where motors are often lightly loaded and also in deviated cold heavy oil PCP applications.
Repair Cost
MPS PM motor stators are on average 50% shorter than an equivalent induction motor stator, with an equivalent reduction in the number of rotors and rotor bearings. This facilitates quick repair and reduced assembly time. MPS PM rotors are very robust and it is highly unlikely that they will ever need to be replaced during any motor repair.
| Series | OD | Max HP (3600 rpm) (Single Section) |
Max. Well Temperature | Max. Winding Temperature | Max. Length | Max. Efficiency |
| 375 | 3.75” | 250 | 350 F | 400 F | 30 Ft. | 92 % |
| 456 | 4.56” | 450 | 30 Ft. | 92 % | ||
| 562 | 5.62” | 1000 | 30 Ft. | 95 % | ||
| 738 | 7.38” | 2250 | 32 Ft. | 96.5 % |
| Series* | OD | Max Torque (300 rpm) (Single Section) |
Max. Well Temperature | Max. Winding Temperature | Max. Length | Max. Efficiency |
| 456 | 4.56” | 740 Ft-lb | 350 F | 400 F | 30 Ft. | 72 % |
| 562 | 5.62” | 1475 Ft.lb | 30 Ft. | 78 % | ||
| 738 | 7.38” | 3300 Ft.lb | 32 Ft. | 87 % |
