VFD Motor Overheating: A Simple Guide for Busy Procurement Managers

Opening a motor panel on a hot day always reminds me how fast things can go wrong when a VFD-driven motor starts running hotter than it should.

VFD motor overheating¹ happens when load, cooling, wiring, or VFD settings push the motor beyond safe temperature limits. Checking load, airflow, parameters, and cable conditions usually solves most cases quickly.

And trust me—busy procurement managers don’t have time to guess where the problem is coming from.

---

What causes VFD motors to overheat?

Sometimes the cause is obvious, sometimes it hides in small details—like a loose terminal that nobody thought to check.

Most VFD motor overheating¹ comes from load issues², poor cooling, wrong VFD parameters, bad wiring, harmonics, motor aging, or VFD hardware faults.

Let’s look deeper so you can spot issues fast—even if you’re not an engineer.

1) Load-related issues

When a motor works harder than it should, temperature climbs quickly.
Excess load, mechanical blockage, or high-inertia equipment often forces the motor to draw more current than its rating, causing rapid overheating.

I’ve seen this happen in Chilean pump houses where a small stone stuck in the impeller made the whole system run like it was dragging a mountain. Suddenly the current jumped, and the motor cooked itself halfway.

Here’s how load problems usually show up:

• Current higher than nameplate
• Bearing wear or poor lubrication
• Pump jamming or partial blockage
• Heavy torque during startup on high-inertia machines

---

Deeper Look

High load forces the motor to generate more torque, and torque requires current. Current generates heat—simple as that.
If the VFD tries to push the motor through a jammed mechanical system, each second adds stress to copper windings and insulation.

For procurement roles, this is important because selecting the right motor size³, correct capacitor system, или proper brake motor avoids 80% of overload cases. At Dongchun, when customers in Peru or Nigeria ask for sizing help, I usually ask for:

• type of machine
• duty cycle
• start/stop frequency
• expected load surges

This lets me match them with an ML, MY, YCL, YC single-phase motor or high-efficiency IE3/IE4 three-phase model that handles overload better. Small decisions here prevent big overheating issues later.

---

2) Poor motor cooling

Cooling problems are the silent killers.

Blocked air ducts, a broken fan, or dust-covered fins prevent proper heat dissipation, causing the motor to overheat even at normal load.

A warehouse in Ecuador once sent me photos of a motor that looked like it had lived inside a flour bag. After cleaning it, the overheating disappeared like magic.

Deeper Look

Cooling depends on clean airflow. When dust, cotton, or oil block the ventilation path, even a motor running at 60% load may reach critical temperature. And if the motor runs at low frequency (<10 Hz), the fan spins too slowly and cooling collapses.

A simple check often solves this:

Cooling Issue	Result
Blocked air inlet/outlet	Rapid temperature rise
Fan damaged or missing	No airflow
Motor surface covered in dirt	Poor heat radiation
High ambient temperature	Reduced safety margin

For long installations—like conveyor lines in South Africa—we sometimes add independent cooling fans⁴ to keep airflow steady even at low VFD speeds.

---

3) Wrong VFD settings

This is one of the top causes—and often the most overlooked by busy managers.

Incorrect V/F curves, high carrier frequency, short acceleration times, or wrong nameplate data create excess current and motor heating.

I remember adjusting one customer’s VFD in Thailand: the carrier frequency was maxed out “because higher sounds better.”
It doesn’t. It just makes more heat.

---

Deeper Look

These settings matter most:

• Carrier frequency⁵ — high value = more IGBT switching = heat
• Torque boost — too high → magnetic saturation
• Acceleration time — too short → current spike
• Incorrect voltage/current parameters → inefficient control
• Long-term operation below 10 Hz → no fan cooling

A good rule:
Enter motor nameplate values exactly as written.

With our high-efficiency IE3 motors (TUV certified), I’ve noticed that correct parameter entry alone lowers temperature by 10–15°C in some installations.

---

4) Cabling and power supply problems⁶

Sometimes the motor is healthy—but the power feeding it isn’t.

Overvoltage, undervoltage, long cables, loose terminals, or poor grounding increase losses and heat inside the motor.

Once, a client from Albania complained about “motor weakness.” We found a terminal so loose it was blackened from heat. A 10-second tightening fixed everything.

Deeper Look

Long cables (>50 m) increase:

• voltage drop
• dv/dt stress
• leakage current

This can cause insulation heating—especially in older motors.

Recommended fixes:

Problem	Remedy
Long cables	Add output reactor or dv/dt filter
Undersized wire	Use thicker shielded cable
Loose terminals	Tighten all lugs
Voltage fluctuation	Check supply quality

---

Заключение

VFD motor overheating usually comes from simple causes: load, airflow, wrong settings, wiring, or aging equipment. If you check these step by step, you can solve most problems fast—even without deep technical knowledge.

---