Inrush Current vs Running Current: What Should Maintenance Technicians Measure Malaysia
Inrush Current vs Running Current: What Should Maintenance Technicians Measure Malaysia
Inrush current and running current are not the same measurement.
Inrush current occurs for a short period when certain electrical equipment starts, while running current is measured after the equipment reaches its normal operating condition.
For technicians troubleshooting motors, pumps, compressors, fans and HVAC equipment, checking both can provide more useful information than measuring running current alone.
A clamp meter such as the TASI TA813B+ True RMS Digital Clamp Meter, which provides both current measurement and an Inrush function, can support these troubleshooting tasks.
What Is Inrush Current?
Inrush current is the temporary high current that can occur when electrical equipment is first energized.
For a motor, the basic sequence is:
Motor OFF
↓
Power ON
↓
High Starting / Inrush Current
↓
Motor Accelerates
↓
Normal Running Current
The inrush event may be brief.
Because of this, simply watching an ordinary current display may not adequately capture the startup event.
What Is Running Current?
Running current is the current consumed after equipment has reached its operating condition.
For example:
A pump starts.
The motor accelerates.
The pump reaches operating speed.
The current then stabilizes.
This stable value is generally the running current being observed during routine inspection.
Inrush Current vs Running Current
The key difference is timing.
MeasurementWhen It OccursWhat It Helps InvestigateInrush CurrentDuring startupStarting behaviourRunning CurrentDuring normal operationOperating load and electrical behaviour
Neither measurement replaces the other.
They answer different maintenance questions.
Why Can Running Current Look Normal Even When There Is a Problem?
Consider this complaint:
“The motor sometimes trips the breaker when we switch it on, but if it starts successfully, it runs normally.”
A technician checks the running current.
Everything appears acceptable.
Does that mean there is no electrical problem?
Not necessarily.
The important event may have occurred during startup.
The troubleshooting sequence should therefore consider:
Startup → Inrush
and
Normal Operation → Running Current
This is one reason inrush measurement can be valuable.
Example: Pump Trips When Starting
Consider a water pump that occasionally trips during startup.
Possible investigation areas can include:
Starting current
Supply voltage
Protection device
Motor condition
Starter or VFD
Mechanical loading
Pump condition
If the technician measures only the normal running current, the startup event may be missed.
Using an Inrush function provides another measurement for the investigation.
Example: Air Compressor
Air compressors are another good example.
A compressor may require substantial motor torque during startup.
Suppose the maintenance team reports:
Compressor starts slowly + occasional breaker trip
Useful information may include:
Inrush Current
Running Current
Supply Voltage
Mechanical Condition
Compressor Operating Condition
The readings should be interpreted together rather than treating one number as the complete diagnosis.
Example: HVAC Compressor
The same principle applies to HVAC systems.
A compressor can experience a different electrical condition during startup than during normal operation.
Technicians may need to determine:
Does the problem happen when starting?
or
Does the problem happen after the compressor is already running?
This distinction immediately changes the troubleshooting direction.
When Should You Measure Inrush Current?
Inrush measurement can be useful when investigating:
Breaker trips at startup
Motor difficult to start
Compressor startup problems
Pump startup problems
Excessive voltage drop during startup
Generator struggling when a motor starts
Equipment taking longer than normal to accelerate
The purpose is to capture what happens during the startup event.
When Should You Measure Running Current?
Running current is useful for:
Routine preventive maintenance
Checking operating load
Comparing similar equipment
Comparing phases
Establishing baseline measurements
Monitoring changes over time
Troubleshooting equipment under normal operation
Running-current trending can be particularly useful in factories with many motors.
Which Measurement Is More Important?
There is no universal answer.
It depends on the problem.
If the complaint is:
“Breaker trips when motor starts.”
Inrush current becomes highly relevant.
If the complaint is:
“Motor has been drawing more current during operation.”
Running current becomes particularly relevant.
If the equipment has both startup and operating problems, technicians may need both measurements.
Build a Starting and Running Current Record
For critical equipment, maintenance teams can record both values.
EquipmentInrush CurrentRunning CurrentStatusPump Motor 01RecordRecordNormalCompressor 01RecordRecordNormalExhaust Fan 01RecordRecordMonitorProcess Motor 02RecordRecordNormal
This establishes a baseline.
Future measurements can then be compared with historical results under similar operating conditions.
Why Baseline Data Matters
Imagine a technician measures 30A on a motor.
Is 30A normal?
Without additional information, the number alone may not answer the question.
Now imagine the maintenance record shows:
Previous inspections: approximately 20A under comparable operating conditions
Current inspection: 30A
That change is much more meaningful.
This is why:
Measurement + History
is often more useful than:
Measurement Alone
Inrush Current Is Not Automatically a Fault
Motors naturally draw higher current during startup.
Therefore:
High starting current does not automatically mean the motor is faulty.
Technicians should consider:
Motor specifications
Starting method
Equipment design
Protection settings
Mechanical load
Supply conditions
Manufacturer information
The purpose of measurement is to provide evidence for troubleshooting.
Running Current Is Also Load-Dependent
Running current can change when the mechanical or process load changes.
For example, a pump operating under one process condition may not draw exactly the same current as it does under another.
Therefore, trending should preferably compare readings taken under reasonably similar operating conditions.
Otherwise, a normal change in load may be mistaken for equipment deterioration.
What About VFD-Controlled Motors?
VFD-controlled motors require additional consideration.
The system becomes:
Power Supply → VFD → Motor → Load
Technicians may need to consider:
VFD operating frequency
Drive fault information
Motor current
Process demand
Mechanical load
The TASI TA813B+ also provides VFD voltage measurement, making it useful for broader drive and motor troubleshooting.
Combine Current and Vibration
Electrical current becomes even more useful when combined with mechanical condition data.
For rotating machinery:
Clamp Meter
→ Inrush Current
→ Running Current
→ Voltage
→ Frequency
Vibration Meter
→ Mechanical vibration
For example:
Running Current Increasing + Vibration Increasing
can justify a closer investigation of the motor and driven machine.
It still does not automatically identify the fault, but it gives the maintenance team stronger evidence.
A Simple Troubleshooting Question
Before selecting a measurement function, ask:
“When does the problem happen?”
If the answer is:
During startup
→ Investigate startup conditions and inrush current.
If the answer is:
While running
→ Investigate running current and operating conditions.
If the answer is:
Both
→ Record both and investigate the complete system.
This simple distinction can make troubleshooting more systematic.
Why TASI TA813B+ Is Useful
The TASI TA813B+ combines:
True RMS
AC/DC Current
Inrush Current
VFD Voltage
Frequency
High/Low-Z
Temperature
DC Zero Adjustment
This makes it useful for technicians working with a variety of electrical and industrial equipment rather than only basic current measurement.
Typical applications include:
Motors
Pumps
Air compressors
HVAC equipment
Fans and blowers
VFD systems
Factory machinery
Important Electrical Safety
Motor and compressor circuits can contain hazardous voltages and high currents.
Measurements on energized equipment should only be performed by appropriately trained personnel.
Always verify the meter's:
Measurement category
Voltage limits
Current limits
Condition
Correct measurement mode
Follow applicable electrical safety procedures and equipment manufacturer instructions.
TASI TA813B+ Inrush Current Clamp Meter Malaysia
Looking for a clamp meter for motor starting current, running current, VFD, pump, compressor 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 electrical and industrial maintenance customers throughout Selangor, Kuala Lumpur, Johor, Penang, Melaka, Negeri Sembilan, Perak, Pahang, Kelantan, Terengganu, Kedah, Perlis, Sabah and Sarawak.
26 Sep 2026
