The duty
A belt conveyor runs at about 1,750 rpm on a 460 V, 60 Hz supply. It needs 9 HP continuously, with load peaks of up to 11.5 HP for up to 20 minutes per shift when product surges. Breakaway torque on a loaded start is about 160 % of running torque.
Step 1 · Nameplate and service factor
The EMPD IE3 motor EM3-132M-4-7.5 on 460 V 60 Hz is nameplated 10 HP, 1,740 rpm, FLA 13.3 A, with SF 1.25 proven by heat run at type test.
Without a service factor, the peaks would push the selection to 15 HP: a heavier, costlier motor running most of its life at 60 % load, where efficiency and power factor fall.
Step 2 · Starting and pull-out torque
Step 3 · Protection settings
For motors with a marked service factor of 1.15 or more, the US National Electrical Code allows the running overload to be set at up to 125 % of nameplate FLA: 1.25 × 13.3 = 16.6 A. Setting it at the SF amps of 15.4 A protects the winding while letting the peaks through.
Step 4 · Mechanical fit and compliance
- IEC frame 132 has a shaft height of 132 mm; the NEMA 215T it replaces has 133 mm. Where the OEM's base is drilled for NEMA, EMPD builds NEMA frames 56C to 256T to MG 1 on request.
- A continuous-duty motor sold in the US must meet NEMA Premium efficiency and be DOE certified. For a 10 HP 4-pole enclosed motor the NEMA Premium nominal value is 91.7 %. The compliance route is a 60 Hz efficiency test by an accredited laboratory and DOE certification before shipment; EMPD discusses this with each US programme.
Result
A 10 HP motor with SF 1.25 replaces a 15 HP selection, runs nearer its best efficiency for most of the shift, and carries the peaks within its proven thermal capability.
Application study: an engineering example worked by EMPD with catalogue data. Your application is confirmed by our engineers before quotation. Send us your duty.
