How to Check Three-Phase Motor Current with TASI TA813B+ Clamp Meter Malaysia
How to Check Three-Phase Motor Current with TASI TA813B+ Clamp Meter Malaysia
Checking the current of a three-phase motor is a common task in factory electrical maintenance.
However, technicians should not simply take one current reading and immediately decide whether a motor is healthy or faulty.
A more useful approach is to measure the individual phases, understand the operating condition and compare the readings with motor information, previous measurements and equipment behaviour.
The TASI TA813B+ True RMS Digital Clamp Meter can be used for current measurement as part of troubleshooting three-phase motors, pumps, fans, compressors and other industrial equipment.
What Is a Three-Phase Motor?
Three-phase motors are widely used in industrial applications because they are suitable for many types of machinery.
Common examples include:
Water pumps
Process pumps
Air compressors
Exhaust fans
Blowers
Cooling tower fans
Conveyors
Production machinery
HVAC equipment
A simplified system may look like:
Three-Phase Supply → Protection → Starter / VFD → Motor → Mechanical Load
A problem anywhere in this chain can affect the motor's electrical behaviour.
Why Measure Motor Current?
Motor-current measurements can help technicians investigate questions such as:
Is the motor drawing current?
Has current increased compared with previous inspections?
Are the phase readings noticeably different?
Does current change when the mechanical load changes?
Is the motor behaving differently during startup?
Is a VFD-driven motor operating as expected?
The current measurement is evidence.
It should be interpreted together with the complete system.
How to Measure Three-Phase Motor Current
Measurements on energized industrial equipment should only be performed by appropriately trained personnel following applicable electrical safety procedures.
The general concept is to measure each phase conductor individually.
For example:
L1 → Measure
L2 → Measure
L3 → Measure
Record the readings instead of relying on memory.
A simple table can be used:
PhaseCurrentL1RecordL2RecordL3Record
The readings can then be compared.
Clamp Only the Appropriate Individual Conductor
This is an important clamp-meter principle.
The jaw should surround the appropriate single current-carrying conductor.
Do not simply place the clamp around the complete multi-core cable containing multiple phase conductors.
The magnetic fields from different current-carrying conductors can interact and result in an incorrect or misleading measurement.
What If L1, L2 and L3 Are Different?
Some variation can occur depending on the system and operating conditions.
However, a significant difference between comparable phase-current readings may justify further investigation.
Possible areas can include:
Supply conditions
Connections
Motor condition
VFD or starter
Electrical imbalance
Mechanical loading
Measurement conditions
Do not diagnose the cause solely from three current numbers.
Use them to determine what should be investigated next.
Example: Factory Pump Motor
Suppose a factory pump is operating, but the maintenance team notices unusual behaviour.
The technician records:
L1 → Current
L2 → Current
L3 → Current
The readings are then compared with:
Previous maintenance records
Motor information
Similar pumps
Current operating load
If one reading differs significantly, the technician can investigate the electrical supply, connections, drive and motor more closely.
Compare with Historical Data
A current reading becomes much more useful when baseline data is available.
For example:
InspectionL1L2L3BaselineRecordRecordRecordMonth 2RecordRecordRecordMonth 3RecordRecordRecordCurrentRecordRecordRecord
The maintenance team can now see whether the motor's electrical behaviour has changed over time.
This is more useful than asking whether one isolated number “looks high.”
Motor Current and Mechanical Load
Motor current is influenced by the work the motor is doing.
Consider:
Motor → Coupling → Pump
If the pump load changes, the motor's electrical behaviour may also change.
Therefore:
Higher Current ≠ Automatically Electrical Fault
Possible mechanical or process causes should also be considered.
The same applies to:
Compressors
Fans
Conveyors
Blowers
Production machinery
Check Running Current and Startup Current
For some problems, normal running current is not enough.
A motor can show acceptable current after it reaches speed but still experience a startup-related issue.
The TA813B+ includes an Inrush Current function.
This allows technicians to investigate:
Motor Startup → Inrush Current
and
Normal Operation → Running Current
Both measurements can be recorded as part of the motor's maintenance history.
Three-Phase Motor Trips During Startup
If the motor trips only when starting, investigate the startup condition.
Possible areas include:
Inrush Current
Supply Voltage
Protection
Starter / VFD
Motor
Mechanical Load
Do not simply replace the breaker with a higher-rated device.
The actual cause and protection requirements should be properly assessed.
Three-Phase Motor Current Is High While Running
If current is higher than historical readings during normal operation, ask:
Has the operating load changed?
Then investigate the system.
For a pump:
Motor → Pump → Process
For a fan:
Motor → Fan → Airflow System
For a compressor:
Motor → Compressor → Air System
An electrical symptom can be caused by a mechanical or process change.
VFD-Controlled Three-Phase Motors
Many industrial three-phase motors are now controlled by Variable Frequency Drives.
The system becomes:
Three-Phase Supply → VFD → Motor → Load
For these applications, technicians may also need to consider:
VFD fault codes
Operating frequency
Motor current
Drive parameters
Mechanical load
Process demand
The TA813B+ provides True RMS and VFD voltage measurement functions, making it relevant for VFD-related troubleshooting.
Always refer to the VFD manufacturer's procedures when performing measurements on drive systems.
Motor Current + Vibration
Electrical and mechanical measurements work well together for rotating equipment.
A practical maintenance approach is:
TA813B+ Clamp Meter
→ Phase current
→ Running current
→ Inrush current
→ Voltage
→ Frequency
plus
Vibration Meter
→ Mechanical vibration condition
For example:
Current Changes + Vibration Changes
can indicate that the machine deserves further investigation.
Neither reading alone automatically identifies the cause.
Motor Current + Temperature
Temperature can provide another useful condition indicator.
Maintenance teams may monitor:
Current + Vibration + Temperature
For important motors, this creates a stronger condition-monitoring record than current measurement alone.
A thermal camera may also be useful when inspecting electrical connections, panels and motor temperature patterns.
Create a Motor Inspection Record
A simple preventive-maintenance sheet can include:
MotorL1L2L3InrushVibrationStatusPump 01RecordRecordRecordRecordRecordNormalFan 02RecordRecordRecordRecordRecordMonitorCompressor 01RecordRecordRecordRecordRecordNormalProcess MotorRecordRecordRecordRecordRecordInspect
Try to take repeated measurements under reasonably comparable operating conditions.
Why TASI TA813B+ for Motor Maintenance?
The TASI TA813B+ combines several functions useful for industrial motor troubleshooting:
True RMS
AC/DC Current
Inrush Current
VFD Voltage
AC/DC Voltage
Frequency
High/Low-Z
Temperature
Resistance
Continuity
NCV
DC Zero Adjustment
This makes it suitable for technicians who need more than basic AC current measurement.
Important Electrical Safety
Three-phase motor systems can involve hazardous voltage and high fault energy.
Only appropriately trained personnel should perform measurements on energized equipment.
Before testing, verify:
Measurement category
Maximum voltage and current ratings
Instrument condition
Test lead ratings
Appropriate PPE
Site electrical safety procedures
Follow the motor, drive and TASI manufacturer's instructions.
TASI TA813B+ Three-Phase Motor Clamp Meter Malaysia
Looking for the TASI TA813B+ True RMS Digital Clamp Meter for three-phase motors, pumps, compressors, VFDs or factory maintenance?
Contact:
MTM Precision Sdn Bhd
Showroom & Service Centre
No 29-1 & 2, Jalan Bandar 18,
Pusat Bandar Puchong,
47160 Puchong, Selangor, Malaysia.
Tel: 03-8080 7172
WhatsApp: +6016-660 7346
Email: mtmpre@yahoo.com
Website: www.mtmpre.com.my
Supporting industrial and electrical customers throughout Selangor, Kuala Lumpur, Johor, Penang, Melaka, Negeri Sembilan, Perak, Pahang, Kelantan, Terengganu, Kedah, Perlis, Sabah and Sarawak.
27 Sep 2026
