Y2 Series 8-Pole Three-Phase Asynchronous Motor

Y2 Series 8-Pole Motor — 750 rpm Maximum Torque Drive

The Y2-*-8 eight-pole motor series produces the highest rated shaft torque of any standard fixed-frequency induction motor in the Y2 family. At 750 rpm synchronous speed (50Hz), a 7.5 kW 8-pole motor delivers approximately 95 N·m of rated torque — nearly four times the torque of a 2-pole motor of identical power. This fundamental torque advantage means a single 8-pole motor can replace a 4-pole motor plus a 2:1 gearbox stage, reducing system cost, space requirements, and drivetrain complexity.

Korea Ever-Power produces 21 standard models in the 8-pole configuration. The range opens at frame 80M (0.18 kW) rather than the smaller 63M or 71M frames used in 2-pole and 4-pole series, because the additional poles require more stator circumference per pole, necessitating a larger minimum frame. The maximum rating of 110 kW is reached at frame 315L.

The low rotor surface speed of 8-pole motors — approximately one quarter that of a 2-pole motor at the same frame — results in very low aerodynamic noise from the external cooling fan. Measured noise levels of 52–82 dB(A) across the 8-pole range are among the lowest achievable with forced-air cooled induction motors, an important consideration for noise-sensitive industrial and marine environments. For speed-controlled 750 rpm applications, our YVF2 VFD motor shares the same IEC frame dimensions.

Maximum Torque Output

At 750 rpm, a 30 kW Y2-250M-8 produces rated torque of (30 × 9550) / 740 = 386.9 N·m. A 4-pole motor of the same power at 1480 rpm produces only 193.5 N·m — exactly half. This doubled torque means heavier loads, higher belt tensions, and larger gearbox input shafts can be handled without oversizing the motor power rating.

Lowest Fan Noise

The cooling fan on an 8-pole motor rotates at 740 rpm — one quarter the speed of a 2-pole fan. Fan aerodynamic noise scales approximately with the fifth power of tip speed, so 8-pole fans produce dramatically lower acoustic noise. The noise range of 52–82 dB(A) across the Y2-8-pole range is the quietest of all standard pole configurations in the Y2 family.

Typical Applications

• Heavy belt conveyors and chain conveyors
• Ball mills and rod mills
• Jaw crushers and hammer mills
• Ship deck winches and anchor windlasses
• Screw conveyors and bucket elevators
• Large industrial fans and exhaust systems
• Low-speed agitators and mixers

Why does the 8-pole range begin at frame 80M rather than 63M?

Eight-pole motors require the largest pole pitch of any standard configuration. Each of the eight poles must be wound into the stator slots around the bore circumference, requiring sufficient bore diameter and slot area for adequate copper fill and magnetic cross-section per pole. At frame size 63M and 71M, the stator bore is too small to accommodate eight poles with practical slot geometry. Frame 80M provides the minimum practical bore diameter for 8-pole winding at useful power output levels, starting at 0.18 kW.

Can an 8-pole motor be used with a gearbox for very low output speeds?

Yes. Starting at 740–750 rpm, an 8-pole motor combined with even a modest 5:1 gearbox delivers an output shaft speed of approximately 150 rpm — suitable for large mixers, slow conveyors, and rotary kilns. With a 10:1 gearbox, output reaches 74 rpm. Our helical gear reducers and worm gear reducers are available in a range of ratios for pairing with 8-pole motors to reach virtually any final output speed.

What is the power factor penalty of using an 8-pole vs 4-pole motor?

8-pole motors have a lower power factor than 4-pole motors of equivalent power because the eight magnetic poles require a higher magnetizing current to maintain the rotating field across the wider air gap. In the mid-power range, a Y2-160L-8 at 7.5 kW has a power factor of 0.75, while a Y2-160L-4 at 15 kW achieves 0.85. This difference in power factor means larger 8-pole motors draw more reactive current from the supply for the same useful output power. Power factor correction capacitors at the motor terminals can compensate if required by site regulations.

Why is the Tst/Tn (starting torque ratio) lower for 8-pole motors than for 4-pole?

Starting torque ratios for 8-pole Y2 motors range from 1.8 to 2.0, slightly lower than the 2.0–2.4 typical of 4-pole models. Despite the lower ratio, the absolute starting torque in N·m is usually higher for an 8-pole motor than a 4-pole motor of the same frame because the rated torque itself is so much larger. For example, the Y2-160L-8 (7.5 kW) has Tst/Tn of 2.0 with rated torque of 99.4 N·m, giving starting torque of 198.8 N·m — well above the Y2-160M-4 (11 kW) starting torque of 158.2 N·m despite the lower ratio.

Are brake motor versions available for the 8-pole range?

Yes. The Y2EJ electromagnetic brake motor series covers 8-pole configurations from frame 80M through 280M. The Y2EJ-*-8 adds a DC electromagnetic disc brake to the standard 8-pole motor, providing fail-safe load holding and rapid deceleration when power is removed. This combination is widely used in hoists, vertical conveyors, and precise positioning systems where the low 750 rpm base speed and high torque of the 8-pole motor must be paired with controlled stopping.