AU2018204677B2

AU2018204677B2 - Mining electrical outlet protection devices test unit

Info

Publication number: AU2018204677B2
Application number: AU2018204677A
Authority: AU
Inventors: Jayesh Patel
Original assignee: Cristaudo Anthony
Current assignee: Cristaudo Anthony
Priority date: 2017-07-24
Filing date: 2018-06-27
Publication date: 2021-12-09
Anticipated expiration: 2038-06-27
Also published as: AU2018204677A1

Abstract

There is provided herein mining electrical outlet protection devices test unit comprising a controller comprising a microprocessor, a memory device in operable communication with the processor, the memory device comprising a plurality of computer program code instruction modules, a user interface in operable communication with the processor; and a plurality of relay control outputs in operable communication with the processor to configure a test circuit configured for fault testing steps of industrial electrical power supply switchboards. The test circuit may comprise a phase selection sub circuit comprising relays controllable by the controller to select one selected phase of three phases at a time for various of the sub-tests disclosed herein. The test circuit is configured for performing any combination of earth continuity, frozen contact, earth leakage lockout earth leakage testing, phase voltage testing and phase rotation testing or singular protection device test to suit a variety of possible configurations of switch board in a comprehensive manner. 12 1/4 3 Connect 8 Earth continuity testing - Initialise 11 User confirm 12 | Open pilot disconnection relay 27 Pilt hot tstnq2|TermFinal module/ remote swtchl ,/*24 Pilot short testing 25 Pilot open testing 26 | Close pilot open/short relay 28 Frozen contact testing 30en lotoen/shortre Earth leakage lockout testing 44 User confirm 31 Perphaserepeat51 Close Phase Selection Rela 4 Perbankrepeat50 CloseELL Relay 4 Earth leakage testing 52 Perphase! | Close PhaseSelectionRela resistor repeat 64 Close Earth leakage relay 62 S Measure response times 63 Phasevoltage esting77 1 .Erh eakqe..cou~~~tn.4 ......... .......................... |I User C onfirm 71 |Read signal fromFilter II/ 72 Display Snapso ofvlte7 P chase rat ionte ting78 1 User Confirm 74 |ead signal from phaserotatio 75 | Disl ay Phase Rotation 76 FIG. 1

Description

1/4 3 Connect 8

Earth continuity testing - Initialise 11

User confirm 12

| Open pilot disconnection relay 27

hot tstnq2|TermFinal Pilt testing Pilot short module/ remote swtchl ,/*24 25 Pilot open testing 26 | Close pilot open/short relay 28

Frozen contact testing 30en lotoen/shortre

Earth leakage lockout testing 44 User confirm 31

Perphaserepeat51 Close Phase Selection Rela 4

Perbankrepeat50 CloseELL Relay 4 Earth leakage testing 52

.Erh eakqe..cou~~~tn.4 ......... .......................... Perphase! | Close PhaseSelectionRela resistor repeat 64 Close Earth leakage relay 62 S Measure response times 63 Phasevoltage esting77 1 |I User C onfirm 71 72 |Read signal fromFilter II/ Display Snapso ofvlte7 P chase rat ionte ting78 1 User Confirm 74

|ead signal from phaserotatio 75 | Disl ay Phase Rotation 76 FIG. 1

Mining electrical outlet protection devices test unit

Field of the Invention

[1] This invention relates generally to mining electrical outlet protection testing. More particularly, this invention relates to mining electrical outlet protection devices test unit.

Background of the Invention

[2] Mining switchboards provide power to various mining equipment and the safety features thereof require regular testing, such as post installation or at periodic intervals.

[3] The present invention seeks to provide a fault test unit for such, which will overcome or substantially ameliorate at least some of the deficiencies of the prior art, or to at least provide an alternative.

[4] It is to be understood that, if any prior art information is referred to herein, such reference does not constitute an admission that the information forms part of the common general knowledge in the art, in Australia or any other country.

Summary of the Disclosure

[5] There is provided herein mining electrical outlet protection devices test unit comprising a controller comprising a microprocessor, a memory device in operable communication with the processor, the memory device comprising a plurality of computer program code instruction modules, a user interface in operable communication with the processor; and a plurality of relay control outputs in operable communication with the processor to configure a test circuit configured for fault testing steps of industrial electrical power supply switchboards.

[6] The test circuit may comprise a phase selection sub circuit comprising relays controllable by the controller to select one selected phase of three phases at a time for various of the sub-tests disclosed herein. The test circuit may be configured for performing various combinations of earth continuity, frozen contact, earth leakage lockout earth leakage testing, phase voltage testing and phase rotation testing or singular protection device test to suit a variety of possible configurations of switch board in a comprehensive manner.

[7] According to one aspect, there is provided a mining electrical outlet protection devices test unit comprising: a controller comprising: a microprocessor, a memory device in operable communication with the processor, the memory device comprising a plurality of computer program code instruction modules, a user interface in operable communication with the processor; and a plurality of relay control outputs in operable communication with the processor to configure a test circuit comprising: a phase selection sub circuit comprising relays controllable by the controller to select one selected phase of three phases at a time; and an earth leakage sub circuit comprising relays controlled by the relay control outputs, the earth leakage sub circuit comprising a relay bank comprising a plurality of resistive loads having differing resistive values and per phase analogue to digital inputs for each phase, the earth leakage sub circuit controllable by the computer program code instructions to connect the relay bank and start a timer; monitor a respective digital input; and calculate an earth leakage trip time using the respective digital input and the timer.

[8] The test circuit may further comprise: an earth leakage lockout sub circuit comprising relays

controlled by the relay control outputs, the earth leakage lockout sub circuit controllable by the

controller to, for each phase selected by the phase selection sub circuit, connect each selected phase

to a plurality of resistive loads having differing resistive values in turn.

[9] The test circuit may further comprise: an earth continuity sub circuit comprising a three phase power supply having a pilot lead and a pilot lead diode and a pilot short/open relay and a pilot diode disconnection relay and wherein the earth continuity sub circuit may be controllable by controller to

selectively disconnect the pilot line diode using the pilot diode disconnection relay and short the pilot

line using the pilot short/open relay.

[10] The earth continuity sub circuit may further comprise a remote switch sub circuit connected

to the pilot lead comprising a remote start relay in parallel with the resistor and a remote stop relay

in series this and wherein the remote switch sub circuit may be controllable by the computer program

code instructions to close the remote stop relay and temporarily close the remote start relay.

[11] The earth continuity sub circuit may further comprise a termination module conductivity sub

circuit comprising termination module connected to the pilot lead in series with termination module

connection relays and wherein the termination module conductivity sub circuit may be controlled by

the controller two selectively close the termination module connection relays.

[12] The test circuit may further comprise: a frozen contact sub circuit comprising relays controlled

by the relay control outputs, the frozen contact sub circuit controllable by the controller to, for each phase selected by the phase selection sub circuit, connect each selected phase to an AC voltage

source.

[13] The AC voltage source may comprise a potentiometer for adjusting a voltage output of the AC

voltage source.

[14] The test circuit may further comprise: a phase voltage sub circuit wherein the controller may

be configured for measuring per phase voltage levels.

[15] The test circuit may further comprise: a phase rotation testing sub circuit comprising a phase

rotation testing microprocessor configured for sampling per phase voltage level signals and detecting

at least one of rising or falling edges of each phase and detecting incorrect phase sequencing.

[16] The phase rotation testing microprocessor may be further configured for detecting

nonuniform duty cycles.

[17] The microprocessor may be further configured for detecting duty cycles having a duty cycles

of less than 30% or greater than 70%.

[18] The phase rotation testing microprocessor may be configured for sampling the per phase

voltage level signals at 500 Hz or more.

[19] The controller may be configured for displaying phase rotation direction.

[20] Other aspects of the invention are also disclosed.

Brief Description of the Drawings

[21] Notwithstanding any other forms which may fall within the scope of the present invention,

preferred embodiments of the disclosure will now be described, by way of example only, with

reference to the accompanying drawings in which:

[22] Figure 1 shows exemplary processing of the controller of the fault testing equipment provided

herein in accordance with an embodiment;

[23] Figure 2 to shows exemplary fault detection circuitry in accordance with an embodiment;

[24] Figure 3 shows an exemplary controller, exemplary relay outputs and associated relays and

analogue to digital inputs in accordance with an embodiment; and

[25] Figure 4 shows an exemplary phase rotation testing circuitry in accordance with an

embodiment.

Description of Embodiments

[26] Figure 3 shows a test unit controller 1 configured for controlling a plurality of relays of a test

circuit 2 shown in figure 2. Figure 1 shows exemplary processing 3 performed by the controller 1 when

implementing various tests.

[27] The controller 1 comprises a microprocessor for processing digital data. In operable

communication with the microprocessor across a system bus is a memory device configured for

storing digital data including computer program code instructions. These computer program code

instructions may comprise a plurality of computer program code instruction modules configured for

performing the various tests described herein with reference to figure 1.

[28] Furthermore, the controller 1 may comprise a digital display device and associated

touchscreen overlay so as to allow for the display of digital data and the receipt of haptic user interface

gestures in use.

[29] In a preferred embodiment, the test unit takes the form of a small form factor battery

powered ruggedised unit which may be deployed in the field when testing switchboards.

[30] The controller 1 controls a plurality of relay outputs 4 connected to associated relay drives 5

which control a plurality of relays 6 when conducting the tests described herein. As can be seen, each

relay 6 is connected to a power supply so as to be selectively energised by the associated relay drive

and relay output 4.

[31] In embodiments, the controller 1 comprises a plurality of analogue to digital inputs 7 which

may be utilised for measuring earth leakage response times.

[32] In the embodiment shown in figure 2, the controller1 comprises 32-bit Flash STM32

microcontroller based on the ARM© Cortex©-M processor.

[33] Turning now to figure 1, there is shown exemplary processing 3 performed by the controller

1. As can be appreciated, the aforedescribed computer program code instruction modules may

comprise a plurality of modules configured for implementing each of the tests described herein.

[34] As will be appreciated from the ensuing description, the controller 1 is configured for stepping the operator through a series of tests including by way of on-screen display and receipt of user

feedback so as to allow the semiautonomous conducting of switchboard testing in a comprehensive

manner reducing likelihood of operator error as may otherwise be the case for manually implemented

testing.

[35] The processing 3 initiates with the connection 8 of the test unit to the switchboard utilising

the appropriate electrical leads. Thereafter, the test unit is initialised 11.

[36] In embodiments, the controller 1 is configured for performing various testing including earth

continuity testing 10, frozen contact testing 30, earth leakage lockout testing 44, earth leakage testing

52, phase voltage testing 77 and phase rotation testing 78. The earth continuity, frozen contact and

earth leakage lockout testing 10, 30 and 44 may be non-live/unpowered testing whereas the earth

leakage testing 52, phase voltage testing 77 and phase rotation testing 78 may be conducted with live

power.

Earth continuity testing 10

[37] In an embodiment, the processing 3 may conduct earth continuity testing 10 which may

initiate with the display of the relevant information and receipt of user confirmation 11.

[38] For earth continuity testing 10, there is shown the circuit 2 comprising a three phase power

supply 13 comprising a pilot lead 14 and an associate pilot lead diode 15.

[39] Furthermore, the circuit 2 comprises an earth continuity testing sub circuit 65 associated with

the pilot lead diode 15 and having a pilot short/open relay 16 and a pilot diode disconnection relay 17

which, as will be described in further detail below, are utilised for shorting and bypassing the pilot

lead diode 15.

[40] In certain embodiments, the earth continuity testing may be required to be implemented

utilising a remote switch and, in this regard, the circuitry 2 may comprise a remote switch sub circuit

18 which may comprise a remote start relay 19 and a remote stop relay 20. As such, for the

performance of such testing, the controller 1 may initially close the remote stop relay 20 and

temporarily close the remote start relay 19 so as to start the remote switch. Opening of the remote

switch may be achieved by the subsequent opening of the remote stop relay 20.

[41] Furthermore, in embodiments, earth continuity testing 10 may be required to be

implemented utilising a termination module 21 and therefore the earth continuity testing sub circuit

may comprise a termination module conductivity sub circuit 22 comprising associated termination

module connection relays 23 which are closed by the controller 1 to connect the termination module

21.

[42] As such, as can be seen, the processing 3 may comprise the control of the termination module/remote switch 24 as is required.

[43] The earth continuity testing 10 may comprise subtests comprising pilot short testing 25 and

pilot open testing 26. For either, the controller 1 may open 27 the pilot diode disconnection relay 17.

[44] As such, for the pilot short testing 25, the controller 1 may close 28 the pilot open/short relay

16 so as to effectively short the pilot lead 14.

[45] The shorting of the pilot lead should result in the display of a fault on the connected

switchboard.

[46] Furthermore, for the pilot open testing 26, the controller may open 29 the pilot short/open

relay 16 so as to effectively float the pilot lead 14. Such should similarly display an associated error

indicator light on the connected switchboard.

[47] The switchboard responses for either test 25, 26 may be recorded by the user utilising the

controller 1.

Frozen contact testing 30

[48] In embodiments, the controller 1 may implement frozen contact testing 30 which may be

conducted subsequent to the earth continuity testing 10. Such may be initiated by the display of

appropriate data and user confirmation 31.

[49] For the frozen contact testing 30, the controller 1 controls the circuitry 2 to inject increasing

voltage on each phase of the three phase supply 13 so as to trigger an associated fault condition of

the connected switchboard.

[50] As can be seen from figure 2, the circuitry 2 comprises a frozen contact testing sub circuit 66

which may comprise an AC voltage source 32 which may comprise an inverter 33 configured to draw

DC voltage from the battery power supply of the test unit and wherein the powering of the inverter

33 may be controlled by associated inverter relay 34.

[51] Associated with the output of the inverter 33 is a potentiometer 35 and associated voltmeter

36 which is controlled by the operator in use to inject increasing AC voltage to each phase.

[52] Furthermore, as can be seen, the frozen contact testing sub circuit 66 comprises phase

selection relays 37 comprising a relay for each of phases A, B and C. Furthermore, the frozen contact

testing sub circuit 66 may comprise a frozen contact relay 38.

[53] It should be noted that the controller 1 controls the phase selection relays 37 so that only one

phase selection relay 37 may be closed at a time so as to prevent interphase shorting.

[54] Furthermore, in embodiments, the circuit 2 may comprise selector relays 39 configured for

selectively connecting the phases to the various testing sub circuits in the manner described herein.

As can be seen, the selector relays 39 comprise relays D and relay E wherein, for the frozen contact testing 30, relay E would be closed and relay D would be open.

[55] As such, the frozen contact testing 30 initiates with the user confirmation 31 wherein, in

embodiments, the user may initially be instructed to dial the potentiometer 35 to the0 V position. As

such, upon user confirmation 31, the controller 1 would close 40 one of the phase selection relays 37

to select, for example, phase A.

[56] Furthermore, the controller 1 would close 41 the frozen contact relay 38 so as to connect the

selected phase to the AC voltage supply 32. Once connected in this manner, the user may be instructed

via the on-screen display to gradually dial up the potentiometer 35 so as to increase the injected

voltage on the selected phase.

[57] In embodiments, the circuit 2 may be configured to inject from 0 to 120 V AC onto each

selected phase.

[58] Simultaneously, the controller 1may close 42 the inverter power supply relay 34.

[59] The user would increase 43 the injected voltage while monitoring the voltage readout on the voltmeter 36 until such time that a fault condition is detected by the switchboard. In embodiments,

the operator may use the controller 1 to control the fault causing voltage.

[60] Thereafter, the process is repeated per phase 44 by way of user confirmation 31 wherein the

controller 1 would then close the next phase selector relay 37 so as to perform frozen contact testing

for each of the phases of the three-phase supply 13.

Earth leakage lockout testing 44

[61] In embodiments, the controller 1is further configured for implementing earth leakage lockout testing 44 which is an unpowered test effectively testing the switchboard relays ability to detect earth faults.

[62] In this regard, the electric circuitry 2 comprises earth leakage lockout testing sub circuit 45 comprising a plurality of resistor selector relays 46 each coupled to an associated resistor of differing resistance. In the embodiment shown, the resistors comprise resistor 9KO to 4MO. (such as of 3.3 MO, 2.7 MO and 9KO.). In embodiments, the resister values may be configured according to application requirements.

[63] Furthermore, earth leakage lockout testing is performed on a per phase basis utilising the phase selector relays 37 operated in turn.

[64] As such, for the earth leakage lockout testing 44, upon receiving user confirmation 47 the controller 1 would close 48 each of the phase selection relays 37 in turn and similarly close 49 each resistor selector relay 46 in turn so as to connect each associated resistor in turn to each phase.

[65] For example, the controller 1 would initially connect the resistor of greatest resistance, being 3.3 M, and then, depending on user feedback, connect 50 the 900K0 resistor and so on until such time that the user indicates that a fault is detected by the switchboard whereafter the next phase would be tested until all three phases have been tested in this manner.

[66] For each phase, each resistor value causing a fault on the associated switchboard may be recorded by the operator using the controller 1 or by the controller 1 itself.

Earth leakage testing 52

[67] In embodiments, the controller 1 may be configured for earth leakage testing 52 and, in embodiments, earth leakage trip response times to plot results to in comparison with the requirements of AS/NZS 4871.1:2012 Clause 2.6 and AS/NZS 4871.1:2012 appendix C.

[68] Now, whereas the aforedescribed tests may be unpowered tests, the earth leakage testing 52 may be a powered test wherein power is supplied via the three phase supply 13.

[69] Furthermore, during the earth leakage testing 52, the controller 1 may be configured for measuring the earth leakage trip response time, and in embodiments, confirm whether such falls within the industry accepted or regulated ranges.

[70] In this regard, the circuitry 2 may comprise resistive banks which may be customisable to suit application requirements corresponding to the interphase voltage wherein, as is shown, the circuitry 2 may comprise a 415 V/110 V interphase bank 53 and a 1000 V interphase bank 54.

[71] The appropriate bank 53, 54 may be selected 55 via the user utilising appropriate jumper

switches which, once done, may be confirmed 56 utilising the interface.

[72] Furthermore, the circuitry 2 may comprise a voltage sensing sub circuit 55 configured to sense

the voltage on each phase. The voltage sensing sub circuit 55 may comprise a voltage isolation barrier

56 and appropriate overvoltage protection circuitry 57 which feed into analogue to digital inputs 58

for each phase. In the embodiment shown, the analogue to digital inputs 58 comprise an analogue to

digital input for each phase and a further input for the earth connection.

[73] Furthermore, each resistor bank 53, 54 comprises toggle switches 59 which may be toggled

by the user to selectively connect associated resistors 60 in turn. For example, for the 1000 V phase

to-phase bank 54, various resistances from 5000 to 15KO are shown.

[74] Again, earth leakage response times are performed on a phase by phase basis. As such, for

the conducting of the earth leakage testing, the controller 1 would close 61 the appropriate phase selection relay 37 to select a particular phase and, while monitoring the input voltage via the

appropriate analogue to digital input 58, close 62 relay E of the selector relays 39 so as to connect the

appropriate phase to the appropriate resistor.

[75] When closing 61 to the selector relay 39, the controller 1 may start a timer with millisecond

resolution and when, by monitoring the relevant phase voltage analogue to digital input, be able to

detect when a trip occurs so as to be able to calculate the response time 63.

[76] In this manner, the measurement of the response times 63 may be performed for various

earth leakage resistances wherein the controller 1 instructs the user to toggle the toggle switches to

connect the appropriate earth leakage resistor. In embodiments, as opposed to utilising mechanised

toggle switches 59, such may be electrically controlled by the controller 1.

Phase voltage testing 77

[77] In embodiments, the controller 1 may be configured for phase voltage testing using a phase

voltage testing sub circuit which converts half wave AC signals from the three phases to half wave DC

signals. A filter may be used to remove noise from the signal.

[78] The signals may be fed into the controller 1 which may be configured for measuring the supply

voltage from the half wave DC signals. The digital display of the controller 1 may display a snapshot of

a number of cycles of the earth voltage to each of the three phases and calculate phase-to-phase

voltages.

[79] In embodiments, the controller 1 may utilise these voltage signals for the earth leakage trip

time measurements described above.

Phase rotation testing 78

[80] In embodiments, controller 1 may be configured for phase rotation testing using the phase rotation testing sub circuit 79 as a substantially shown in Figure 4.

[81] The phase rotation testing sub circuit 79 comprises a resistive divider and overvoltage input circuit 81 for each of the phases which fit into a microprocessor 80.

[82] The microprocessor may sample the phase inputs at 500 Hz or more to measure the times of between rising edges of the face signals to determine the sequence of the phases.

[83] In embodiments, the microprocessor 80 may be programmed to detect a missing phase, such as for example, if the microprocessor 80 detects a rising edge on Phase A and then on phase C, indicative that phase B has failed to rise.

[84] In embodiments, the microprocessor 80 may be programmed to detect phases in the incorrect order such as, for example, if Phase A rises, then Phase C rises and then Phase B rises.

[85] In embodiments, the microprocessor 80 may be configured for detecting non-uniform duty cycles of the phases such as, for example, phases less than 30% of greater than 70%.

[86] If detecting an error, the microprocessor 80 may output an error using output 82 which is read by the controller 1. In embodiments, the controller may be able to display the phase rotation vector on-screen (such as clockwise or counterclockwise).

[87] The foregoing description, for purposes of explanation, used specific nomenclature to provide a thorough understanding of the invention. However, it will be apparent to one skilled in the art that specific details are not required in order to practice the invention. Thus, the foregoing descriptions of specific embodiments of the invention are presented for purposes of illustration and description. They are not intended to be exhaustive or to limit the invention to the precise forms disclosed; obviously, many modifications and variations are possible in view of the above teachings. The embodiments were chosen and described in order to best explain the principles of the invention and its practical applications, they thereby enable others skilled in the art to best utilize the invention and various embodiments with various modifications as are suited to the particular use contemplated. It is intended that the following claims and their equivalents define the scope of the invention.

Claims

Claims 1. A mining electrical outlet protection devices test unit comprising: a controller comprising: a microprocessor, a memory device in operable communication with the microprocessor, the memory device comprising a plurality of computer program code instruction modules, a user interface in operable communication with the microprocessor; and a plurality of relay control outputs in operable communication with the microprocessor to configure a test circuit comprising: a phase selection sub circuit comprising relays controllable by the controller to select one selected phase of three phases at a time; and an earth leakage sub circuit comprising relays controlled by the relay control outputs, the earth leakage sub circuit comprising a relay bank comprising a plurality of resistive loads having differing resistive values and per phase analogue to digital inputs for each phase, the earth leakage sub circuit controllable by the computer program code instructions to connect the relay bank and start a timer; monitor a respective digital input; and calculate an earth leakage trip time using the respective digital input and the timer.
2. The test unit as claimed in claim 1, wherein the test circuit further comprises: an earth leakage lockout sub circuit comprising relays controlled by the relay control outputs, the earth leakage lockout sub circuit controllable by the controller to, for each phase selected by the phase selection sub circuit, connect each selected phase to a plurality of resistive loads having differing resistive values in turn.
3. The test unit as claimed in claim 1, wherein the test circuit further comprises: an earth continuity sub circuit comprising a three phase power supply having a pilot lead and a pilot lead diode and a pilot short/open relay and a pilot diode disconnection relay and wherein the earth continuity sub circuit is controllable by controller to selectively disconnect the pilot line diode using the pilot diode disconnection relay and short the pilot line using the pilot short/open relay.
4. The test unit as claimed in claim 3, wherein the earth continuity sub circuit further comprises a remote switch sub circuit connected to the pilot lead comprising a remote start relay in parallel with a resistor and a remote stop relay in series with the remote start relay and wherein the remote switch sub circuit is controllable by the computer program code instructions to close the remote stop relay and temporarily close the remote start relay.
5. The test unit as claimed in claim 3, wherein the earth continuity sub circuit further comprises a termination module conductivity sub circuit comprising termination module connected to the pilot lead in series with termination module connection relays and wherein the termination module conductivity sub circuit is controlled by the controller two selectively close the termination module connection relays.
6. The test unit as claimed in claim 1, wherein the test circuit further comprises: a frozen contact sub circuit comprising relays controlled by the relay control

outputs, the frozen contact sub circuit controllable by the controller to, for each phase selected by

the phase selection sub circuit, connect each selected phase to an AC voltage source.
7. The test unit as claimed in claim 6, wherein the AC voltage source comprises a

potentiometer for adjusting a voltage output of the AC voltage source.
8. The test unit as claimed in claim 1, wherein the test circuit further comprises:

a phase voltage sub circuit wherein the controller is configured for measuring per

phase voltage levels.
9. The test unit as claimed in claim 1, wherein the test circuit further comprises:

a phase rotation testing sub circuit comprising a phase rotation testing

microprocessor configured for sampling per phase voltage level signals and detecting at least one of

rising or falling edges of each phase and detecting incorrect phase sequencing.
10. The test unit as claimed in claim 9, wherein the phase rotation testing microprocessor is further configured for detecting nonuniform duty cycles.
11. The test unit as claimed in claim 10, wherein the microprocessor is further

configured for detecting duty cycles having a duty cycles of less than 30% or greater than 70%.
12. The test unit as claimed in claim 9, wherein the phase rotation testing

microprocessor is configured for sampling the per phase voltage level signals at 500 Hz or more.
13. The test unit as claimed in claim 9, wherein the controller is configured for

displaying phase rotation direction.