Motor

Insulation

Type of mounting and dimensions

Foot, flange or face mounting, and combinations are offered. Dimensions of squirrel cage types, are given in the catalogue of standard motors, while those of slipring types are included herein.

Three phase, 415 Volts 50Hz supply with * 10%, Voltage & * 5% frequency variation, and 40*C ambient temperature. Motors for voltages from 220V to 550V frequencies from 50Hz to 60Hz, higher ambient temperatures are suited for wider power supply variations, can also be given on request.

Voltage, frequency and ambient temperature

Totally enclosed fan cooled (TEFC) with degree of protection IP54 upto 132 frame size & IP55 for 160 & above frame sizes as per IS:4691. IP55 or IP56 on request.

Enclosure

Squirrel cage rotors are of die cast Aluminum material for low starting currents with high starting torques, suitable for the large no. of starts/stops required.

a) 1LB3 for squirrel cage rotors and
b) 1LT3 for Slip Ring (Wound) rotors.

The motors are identified by the type reference,

The common Cyclic Duration Factors (CDF) for the above duties are 25%, 40%, 60% and 100%. We also supply, on enquiry, motors for other CDFs. The CDF calculations are shown in figures 1(a), 1(b) and 1(c). Unless otherwise specified, a duty cycle is ten minutes long.

Rotor type and identification of motors

We also supply motors for special types of duties, on enquiry, including multi-speed motors with squirrel cage rotors.

This includes a period of starting, a period of operation at constant load, a period of electrical braking, and a de-energised period, which are too short to obtain thermal equilibrium during one duty cycle. It is understood that the starting affects temperature rise as in (b) above, and the stopping also affects temperature rise as braking is carried out electrically.

c) Intermittent duty with electrical braking (S5) {Fig 1(c).}

This includes a period of starting, a period of operation at constant load and a de-energised period, which are too short to attain thermal equilibrium during one cycle. The starting affects temperature rise, as load GD* is higher than rotor GD* and/or no. of starts/hour is high, for this type of duty. The motor is stopped after switching off, either by natural deceleration, or by a mechanical brake, without additional heating of the windings.

b) Intermittent duty with starting (S4) {Fig 1(b).}

Tables given herein are for load GD* equal to or less than rotor GD*. For cases where load GD*>rotor GD* the motor should be selected from the table with a higher no. of starts/hr. As per the formula: no. of starts allowed = no. of starts as per table X 2 X GD* of rotor / (GD* of rotor + GD* of load).

This includes a period of operation at constant load and a de-energised period, which are too short to attain thermal equilibrium during one cycle. The starting current does not significantly affect the temperature rise for this type of duty.

a) Intermittent periodic duty (S3) {Fig 1(a).}

Suitable for diverse duties

The size of motor is governed by mechanical effects of starting and braking functions, the type of control and the number of switchings per hour. The rated output, the number of starts/hour and the inertia (i.e load GD* + rotor GD*) are independent.

They conform IS:325 for Three phase induction motors and IS : 4722 for Rotating Electrical Machines.

They are also used for applications such as material handling, weirs and sluices Irfts of all types: and all auxiliary motors in rolling mills or wherever intermitted drives are required.

Crane and Hoist duty motors from Bharat Bijlee are ideal for frequent starts/stops and reversing.

Introduction