Ms. Ori! I just now received an inquiry from a customer who said that the motor he was operating suddenly stopped. It looks like the one you are using is a KII Series 25 W induction motor. I can't believe it suddenly stopped... It's not realistic, isn't it?
Well, induction motors is continuous rating, and that's also written in the catalog. It means that you can keep it running for 24 hours. Normally, if you're operating at a torque within the specification range, you wouldn't expect the motor to stop.
You're right. Ah! That reminds me, the customer told me that an object accidentally caught in the equipment and the motor shaft became locked.
Maybe that's the reason!? Do you know that in case of KII Series, motors over 15 W come with thermal protector?
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In the catalog, the ones marked with "TP" are the ones with a built-in thermal protector in the motor. (The 6 W motor [for the KII Series] is impedance protected, which provides overheat protection*.
A thermal protector is one of the overheat protective devices built into the motor, and when the winding temperature of the motor exceeds a certain level, it automatically cuts off the contacts to stop the motor.
I see. What is the thermal protector for?
That's because if the input increases due to any cause, such as when the motor is locked by overload or otherwise constrained, or when the ambient temperature rises rapidly, or for some other reason, the temperature of the motor will rise rapidly. If you leave it in that state, the insulating performance inside the motor will deteriorate, shortening its lifetime and possibly causing winding burnout. In order to protect the motor from such situations, it is equipped with an overheat protective device. All motors that comply with overseas safety standards have this feature.
I see. It's a protective device intended to prevent motor burnout due to heat generation. But, Ms. Ori, you said earlier that the thermal protector activates when the temperature exceeds a certain level, but at what temperature does the thermal protector activate?
In the case of the KII Series, the specification is that the contacts open when winding temperature inside the motor is 130 °C ±5 °C, and then when the temperature drops the contacts close at 85 °C ±20 °C. However, some models have different operating temperatures, it is better to check the specifications of each motor's overheat protection device for more details.
Yes.
In case of the customer that Vex contacted earlier, the shaft of the motor remained continuously locked up, right? If so, maybe the motor generated heat abnormally due to overload, and ended up exceeding a certain temperature.
Indeed, that seems to be the most likely scenario. Wait. But Ms. Ori, if you leave it after the motor stopped, the temperature will naturally drop, right? Does that mean that once the contacts are cut off and the motor stops, it will automatically start operating again?
That’s right. But for some customers, it's better not to reset automatically. In such cases, it will be good idea to use the SB50 W brake pack in combination. The SB50 W has a thermal protector open detection function that prevents the motor from restarting automatically. So you can use it without worrying! Also, the SB50 W's thermal protector open detection function outputs an alarm signal when the motor's thermal protector operates and the motor stops, so you can use this signal as well.
I see.
Why don't you recommend to the customer?
Yes I will! I'll talk to the customer as soon as I can!
