View Full Version : overload protection

18-07-2012, 01:10 PM
I have, rightly or wrongly, just bought a Chinese VFD & spindle. Can anyone tell me if the following thermal overload relay would protect it in the case of jamming etc. If not is there any way of doing this?

The product is mainly applicable to a circuit of AC 50Hz/60Hz, rated working voltage up to 690V and current from 0.1A to 630A, used to protect a motor from overload, phase-failure, extra-long time starting and extra-long time jam. It can be installed inserting in a corresponding AC contactor or be installed independently.NR2(JR28) series relays can replace JRS1 series thermal overload relays.

18-07-2012, 03:29 PM
Is the spindle one of the water cooled 2.2kw types seen on Ebay? I seem to recall that there is a setting in the VFD that relates to thermal protection...

18-07-2012, 06:16 PM
When you set any VFD up you have to enter a current limit - this is the maximum current that can be drawn, so if it is exceeded the VFD will cut the power and display an error. For the Chinese VFD it would display E.l.o.c.
You must not put a relay between the VFD and it's mains supply since if the supply is cut whilst running there's a strong chance it will be broken.

19-07-2012, 10:35 AM
Thanks for the replies, it is one of the Chinese, air cooled 1.5kw. This is more of a hobby nowadays and I would have preferred to buy one made closer to home, but my budget will not stretch to it. So I wait with fingers crossed. I have a little Trend router but it is so noisy!

19-07-2012, 06:17 PM
air cooled 1.5kw. [...] I have a little Trend router but it is so noisy!

Most of the noise from a motor comes from the fan, so you wont find the 1.5KW air cooled spindle to me much quieter than the Trend router. Cutting noise is often as big if net greater than the noise from the spindle. A water cooled spindle would be, plus with the water cooled spindle you can run it down to low speeds without it overheating, unlike the air cooled spindle where the fan cannot provide enough airflow to cool the spindle at low speeds.