Big motor heating problem

[Aldomili]

Hi guys I have a big problem with 3-phase induction motor in star connection
The motor power is 3-hp
When the motor is starting periodically (many times per minute) it is over heating after 10 minutes from start of working. If the motor is in continuous operation it doesn't heat but if it operates in separate operations its over heating and generate sounds like beep in all times it started please help me to solve this problem .

 

[Lucien Nunes]

Motors are often rated for a specific maximum number of starts per hour, depending on the type of load.

• What does it drive?
• Is it the original / correct type of motor?
• Was it designed for that number of starts per hour?
• Is it started direct on line?

 

[Pete999]

Motors are often rated for a specific maximum number of starts per hour, depending on the type of load.

• What does it drive?
• Is it the original / correct type of motor?
• Was it designed for that number of starts per hour?
• Is it started direct on line?

As always Lucien asks all the right questions

 

[Aldomili]

Motors are often rated for a specific maximum number of starts per hour, depending on the type of load.

• What does it drive?
• Is it the original / correct type of motor?
• Was it designed for that number of starts per hour?
• Is it started direct on line?

It drives by Yaskawa Inverter
Its the original motor but its China motor it doesn't has a name plate on it
It generates beep sound at each start multiple times

 

[plugsandsparks]

Its very hard to guess accurately from a keyboard as there are many variables not apparent to me.
Here are a few ideas to consider.
1. Motor overheats because the nature of starting generates large currents = large IR losses that cannot be removed because the fan on the motor is not turning fast enough.
Consider additional cooling to the motor via separate fans.
2. As it is inverter driven, hopefully the inverter can be configured to reduce acceleration target and thus allow for a much gentler start. This really depends what the motor is connected to. Consider contacting Yaskawa for parameter settings for reduced current starting.
3. Again depends what the motor is connected to, can a clutch be incorporated between the motor and load to allow motor to continue to run. There may be safety issues to consider here.
4. As the motor is an unknown, it could be that the motor is not suitable for your local voltage, consider buying a new motor locally for your supply and as mentioned above check with motor manufacturer like ABB for duty cycle.
5. You mention motor is connected in star worth checking this is how the invertor is expecting it to be connected.
6. You mention a beeping, assume this is from the invertor having determined motor is too hot. Is the motor actually too hot ? - If you touch the motor casing is it too hot to hold onto or can you hold your hands onto the casing, it could be the invertor again is not set correctly as is detecting an overload condition which is too sensitive.

Good Luck and Happy new year

 

[Darkwood]

The beeping if from the motor is often high frequency resonance due to it been inverter driven, often when this is a problem their is a setting in the drive where you can alter the waveform slightly, it can also be caused by poor motor design or cheap drive components.

I suspect if you can satisfy Luciens questions and that the motor is designed for the duty it is subject to then it possible has a hot spot in the windings that is sensitive to a preset speed/frequency or is accumulating heat in a runaway effect because the of the constant starting and stopping.

When you bring up the origin and lack of nameplate etc then this rings many alarms of just been a cheap import fake which I have come across so many times in this industry.

The last motor from china I opened from an imported lathe had bamboo divides in the windings that had broken down and led to the demise of the motor.

 

[marconi]

What method of motor control is selected? Look at the A1-02 setting. The factory default setting is A1-02 = 02 which means 'open loop vector' control. A possible way to reduce the overheating problem is to change the motor control method to V/f or 'voltage-frequency' by setting A1-02 = 00. But be careful not to change it until you have confirmed with the manufacturer what method of motor control is required for the application/load the motor is driving.

Also, has 'autotuning' been done for the inverter to 'learn' the motor electrical and mechanical characteristics? Autotuning is done by the selecting this mode in the inverter menu - but before doing an autotune you have set some constants which are dependent on the specification of the motor so you need details of the motor - see setting T1-00 to T1-08 - such as number of poles, rated current, rated voltage, rated power, base speed....

 

[Andy-1960]

What speed is the motor being run at? If it is too slow it will not be cooled by its fan, if it’s too fast this could result in overload.

 

[PEG]

I think all the above,good advice,is very dependant on the motor not having bamboo inserts and a marzipan core.....as Darkwood pointed out.

 

[Vortigern]

What a treasure trove of knowledge we have here.

 

[Aldomili]

Sorry quys I tried all above solution but not success

 

[marconi]

Could you answer some or all of Lucien Nunes' questions in #2 please?

Has the overheating only just started to be a problem?

Have you measured the insulation resistance of the windings?

Does the rotor turn freely or is it hard to turn?

To help you we need you to provide more background and information. Some pictures would be very helpful.

 

[marconi]

How long is the cable between the ouput of the inverter drive and the motor terminals? It must not be longer than about 20m. The reason is that the pulses of voltage being sent to the motor could be reflected back to the inverter because of impedance differences. The reflected pulses - those going in the direction from the motor to inverter output - could then add to the forward going pulses which will raise the maximum voltage at the motor terminals and increase too the rate of rise/steepness of the voltage dV/dt - neither of these two voltage rises will do the motor's winding insulation any good over the life of the motor.