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103-4E Issue 2 Spare parts, installation and maintenance of ac electric induction motors

Noise levels

The noise levels published in current Sales

Specifications are equal to or less than the

limiting values for rotating machines

specified in European and International

Standards BS EN 60034 and IEC 34-9.

In most cases noise levels also meet limiting

values for exposure to noise in the work

place i.e. Guidance on regulations for Noise

at Work issued by HMSO.

It is the responsibility of the purchaser to

ensure that other overriding lower noise

levels if required, eg Machinery Directive,

are specified at the time of order, or that the

installation incorporates noise attenuating

measures.

Free rotation

The rotor must be free to rotate within

its housing. Where uneven or bumpy

rotation occurs the bearings should be

inspected to establish that they have not

been damaged during transportation or

storage.

Slide rails

Slide rails are available for all motors in the

Brook Crompton product range to provide

adjustable mounting. Fabricated steel rails

are the standard as they are suitable for all

mounting arrangements. Alternative

aluminium slide rails are available for floor

mounting.

Installation

1 slide rails must be installed on a flat

surface

2 rails must have a secure location

3 drive and driven shafts must be parallel

Electrical connection

The connection diagram is shown on the

leaflet enclosed in the motor terminal box or

the diagram inside the terminal box lid. The

cables used should be capable of carrying the

full load current of the motor (see motor

name-plate) without overheating or undue

voltage drop.

Cable terminations

All cable terminations should be tightly

secured. Mains lead terminal lugs should be

in face to face contact with the motor lead

lugs and securing nuts and lockwashers

screwed firmly over the connection. There

should be no nuts or lockwashers fitted

between the mains and motor lugs.

Wiring should be carried out or checked by a

qualified electrician and equipment must be

earthed in accordance with current

regulations. The equipment must be

correctly fused and isolated. All covers must

be in position prior to running.

WARNING

Isolate power supply to motor before

commencing any routine cleaning or

maintenance work.

Drying out procedures

It is preferable to dismantle the motor

to the point where the rotor is removed.

This is not essential but the drying out

process will take longer in the assembled

state.

The temperature of the windings and the

insulation resistance should be monitored

at regular intervals. On initial application

of heat the insulation resistance will drop

quickly and then start to rise slowly until

level. On discontinuation of the drying

process, a further rise in resistance will

occur.

There are several methods which can be

used:

1 place the motor in a warm (typically 40°C),

dry airstream (fan or convector heater) or

in a warm oven with a temperature not

exceeding 80°C. This method is preferred

if the motor is dismantled

2 connect the motor to a low voltage* three

phase supply and inject a current not

exceeding 50% of the full load current into

the stator winding (*approximately 10%

of the line voltage). If this is carried out on

an assembled motor, it is possible though

unlikely that the motor will turn. If so the

rotor should be locked in position

3 connect two phases in parallel, and the

third in series. Apply a low voltage a.c. or

d.c. supply up to a maximum of 50% of

full load current. The stator winding

temperature must not be allowed to

exceed 80°C. In practice the frame should

not be hot to the touch, to guard against

internal overheating and consequent

damage to the insulation

4 where heaters are fitted these can be

energised

Supply

It is important that a motor is operated

within the limits of its design voltage and

frequency.

Standard motors for the UK will operate

without damage on any voltage in the range

94% to 106% of the nameplate voltage.

The supply cables must be capable of

carrying the full load current of the motor

(see motor nameplate) without overheating

or excessive voltage drop under starting

conditions.

Earthing

All motors are fitted with an earthing

terminal, in or adjacent to the terminal box,

to enable connection to an effective earthing

bond. The terminal is designed for

connecting the correct size of copper earth

connector. If a different material is to be used

please refer to Brook Crompton.

The motor must be earthed by connecting

the shortest possible length of cable to the

earth screws. The cable must have a

capacity at least that of the main connections

up to 16mm

phase conductors. Between 16

and 35mm

phase conductors, the earth

should be a minimum of 16mm

. Above

35mm

phase conductors, the earth

conductor should be a minimum of half the

phase conductor.

An earthing bond should not be

terminated under the motor fixture

bolts or terminal cover screws. The

earth lead could be over-looked on

reconnection after maintenance

Heater continuity

Heaters should be checked for continuity

prior to connection to the control circuitry.

Thermistor continuity

If fitted, it is recommended that thermistors

be connected to the control circuit.

Thermistors provide good thermal overload

protection.

Auxiliary electrical items

Where auxiliaries are fitted, the

characteristics should be checked. Example:

RTDs (Resistance Temperature Detectors)

should have their resistances checked

against manufacturer’s figures.

Do not megger across the thermistor. Do not

apply more than 6V across the thermistor for

continuity check.

up to 16

16-35

above 35

Phase conductor

at least equal

16 minimum

at least half

Earth conductor

Installation and maintenance of

ac electric induction motors

1 2 3 4 5 6 7 8 9 10 11 12

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