MIL-DTL-17060G(SH)
TABLE X. Locked - rotor torque, design C.
Synchronous speeds (r/min)
hp
1800
1200
900
1
---
---
---
1½
---
---
---
2
---
---
---
3
---
250
225
5
250
250
225
7½
250
225
200
10
250
225
200
15
225
200
200
20 through 200
200
200
200
3.6.6.1.3.5 Design FF. With rated voltage and frequency applied, the locked-rotor torque of design FF motors
shall be not less than 115 percent or more than 155 percent of full-load torque.
3.6.6.1.3.6 Design B7. With rated voltage and frequency applied, the locked-rotor torque of design B7 motors
shall be not less than 70 percent of full-load torque.
3.6.6.1.4 Locked-rotor current. The locked-rotor current for 440-Vac motors with standard horsepower ratings
shall be in accordance with the values specified in table XI. For other than 440-Vac motors, the locked-rotor current
shall be proportional to the ratio of 440 volts divided by the applicable rated voltage. Motors shall withstand
locked-rotor current at rated voltage for 20 seconds. For 440-Vac motors furnished in other than standard hp
ratings, the maximum locked-rotor current shall be in accordance with the following equations:
a.
DPP enclosures:
Below 20 hp - I1r = (7.69 × hp) + 7.8
Above 20 hp - I1r = (7.61 × hp) - 1.7
b.
All other enclosures:
Below 20 hp - I1r = (8.46 × hp) + 8.6
Above 20 hp - I1r = (8.37 × hp) - 1.9
3.6.6.1.4.1 Design A. The locked-rotor current of design A motors shall meet the requirements of 3.6.6.1.4
except the locked-rotor current shall be not greater than the values specified in table XI by more than 25 percent.
3.6.6.1.4.2 Design B7. The locked-rotor current of design B7 motors shall meet the requirements of 3.6.6.1.4
except the locked-rotor current shall be not greater than the values specified in table XI by more than 5 percent.
3.6.6.1.4.3 Design FF. The locked-rotor current of design FF motors shall meet the requirements of 3.6.6.1.4
except the locked-rotor current shall be not greater than 67 percent of the values specified in table XI.
3.6.6.1.5 Slip. Unless otherwise specified (see 6.2), design A, B, B7, C, and F motors shall have a slip at rated
load of less than 5 percent, except for design A and B and B7 motors with 10 or more poles which shall a slip at
rated load not greater than 6 percent. Design D motors shall have a slip at rated load between 5 and 13 percent of
rated speed. (For 2-pole, TEFC pump motors 100 hp and greater see 3.5.2.3).
3.6.6.2 Multispeed motors. Unless otherwise specified (see 6.2), multispeed motors in which any of the speeds
are obtained by reconnecting the windings or by separate windings shall be as specified in 3.6.6.2.1 through
3.6.6.2.1 Two-speed motors. Locked-rotor current, torque, and slip requirements shall be the values specified
in table XII.
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