8/14/2019
Identifying_Leads_of_Nine_Lead_Three_Phase_Motor.doc
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Identifying Leads of a Nine Lead Three Phase Motor
Question: I have lost track of the leads of a nine lead three
phase motor. How can I re-identify these leads?
Answer: For the purpose of this test, a lantern battery of six
or nine volts works best. Use a ! volt-ohmmeter with a "#$ ohms per
volt ! scale. %attery and voltmeter leads should be properly
identified. &lli'ator
clips should be used on both. (he motor must be completely
assembled. (est the nine leads for continuitywith the ohmmeter to
determine whether the motor is star )wye* or delta connected. (he
delta connectedmotor will possess three sets of three leads with
continuity between them. +n the other hand, the starconnected motor
will have only one set of three leads with continuity between them,
and three sets of twoleads with continuity. Followin' are specific
steps to take when identifyin' leads of both a star connectedand a
delta connected motor. efer to the dia'rams on the followin' pa'e
for further details.
Delta Connected Motor:
Usin' an ohmmeter, identify the three 'roups of three leads.
eparate these 'roups by tyin' them with tape. &ttach leads to a
pair of wires in a 'roup, and observe the volta'e drop from each
pair of ener'i ed leads tothe third lead in that 'roup. !ontinue
until a combination is found that 'ives a volta'e drop from each of
theener'i ed leads to the third lead e/ual to one half of the
battery volta'e. (he lead located halfway betweenthe other two will
thus be the corner lead of the delta. epeat this for each 'roup of
leads, markin' the
corner leads 01, 0", and 02.
3ext, use the inductive kick test method to identify the proper
markin's for the other two leads of each'roup. (he two coils 02 4
05 and 02 4 06, actin' in parallel, will produce the effect of a
coil positionedhalfway between the actual position of the two
coils. (he flux produced by 02 4 05 and 02 4 06 combined,will be
perpendicular to the axis of 01 4 07 and 0" 4 08. +penin' and
closin' a switch in this circuit willproduce a kick in coils 01 4
09 and 0" 4 0:, but no kick in 01 4 07 and 0" 4 08.
(herefore, if the battery is connected from 02 4 05 and 02 4 06
as shown, openin' and closin' the batterycircuit, the voltmeter
will identify leads 01, 07, and 09 and can be distin'uished by
notin' the ma'nituderather than the polarity. (he voltmeter can
then be connected to terminal 0" for determination of the leads0: 4
08. ;eads 0" to 08 will 'ive little or no deflection, and leads 0"
to 0: will 'ive a substantial deflection.
In succession, the battery is then transferred to the corner of
01. (ie the battery between leads 01 4 07 4
09. or deflection. (his pair of leads consists of the 01 4 07
leads. 3ext,move the battery to the 08 4 06 combination, with the
positive lead on the 08 lead and the ne'ative lead tobe used for
flashin' the 06 lead. (he voltmeter is so placed on the 01 4 07
pair that an upscale deflection is
observed on the >make> of the ne'ative 06 lead. (he
voltmeter positive lead is then the 01 motor lead, andthe ne'ative
voltmeter is the 07 motor lead.
3ext, move the battery to 08 4 09 leads with the positive lead
on the 09 motor lead, and the ne'ative toflash the 08 lead.
Identification of the 02 motor lead is then determined by an
upscale kick. (he positivevoltmeter lead should be on this lead,
and the ne'ative lead should be on the 05 motor lead. hift
thebattery to the 06 4 09 pair, with the positive battery lead on
the 06 lead and the ne'ative used for theflashin'. &n upscale
kick will identify the 0" motor lead. (he positive voltmeter lead
will be found on the 0"lead, and the ne'ative voltmeter lead will
be the 0: lead. (his concludes the lead testin' of the nine
leadstar connected motor.
