Thermal / overcurrent protection on high voltage DC motor

[Electronic Swear]

There is a DC motor with a rectified 220VAC input source.
When there is a rotor locking, the current of course will
increase sharply and thermal effect is happened.

I have tried to continous locking the rotor of this DC
motor, it will hot up in a very high temperature. Around
10 second, the motor has burnt and in fire.

I am now thinking that how to protect the motor when there
is a rotor locking happened. Of course, fuse can be 1 of
the solution, but it is not good for only 1 time protection
provided.

Any good suggestions (most simplest) can be provided?
I suppose to use PTC in series with the motor teriminal.
However, I am afraid the time respone / size / cost of PTC
will not be good for me. The motor current is about 5A at
rotor locking. For normal operation, it should be around 1A.

Thank~

 

[Frithiof Andreas Jensen]

Any good suggestions (most simplest) can be provided?

A Motor Protection Relay is the simplest - it's an electromechanical device
that emulates the temparature rise of a motor given it's load, which is
proportional to the current drawn. This device will catch a "fast" error
such as a locked rotor as well as overload, too high duty-cycle etc.

One buys them based on the rating of the motor.

 

[R.Legg]

There is a DC motor with a rectified 220VAC input source.
When there is a rotor locking, the current of course will
increase sharply and thermal effect is happened.

I have tried to continous locking the rotor of this DC
motor, it will hot up in a very high temperature. Around
10 second, the motor has burnt and in fire.

I am now thinking that how to protect the motor when there
is a rotor locking happened. Of course, fuse can be 1 of
the solution, but it is not good for only 1 time protection
provided.

Any good suggestions (most simplest) can be provided?
I suppose to use PTC in series with the motor teriminal.
However, I am afraid the time respone / size / cost of PTC
will not be good for me. The motor current is about 5A at
rotor locking. For normal operation, it should be around 1A.

This is probably too high a current for a PTC to pass normally, while
withstanding the operating voltage specified.

Better to check out thermal fuses or thermal switches. The one-shot
thermal fuse is typically less than two bucks.

RL

 

[Frithiof Andreas Jensen]

Can you give me more detail on the regarding components?

ABB does them:
http://www.abb.com/global/abbzh/abb...e=us&m=9F2&c=C58758CE02F8CABFC1256DA200335B03

As do Siemens:
http://www.ad.siemens.de/cd/is_schuetzen/html_76/ueberlastrelais.htm

I suppose to have as simple as possible solution on how to
prevent over-heat/ current on DC motor locking. And fuse is not
a good suggestion for me because it is only for 1 shot used.

They are not fuses - they act like a resettable fuse where one can define
the I2t curve to match the load.

 

[legg]

I suppose to have as simple as possible solution on how to
prevent over-heat/ current on DC motor locking. And fuse is not
a good suggestion for me because it is only for 1 shot used.
Of course, it is not convenience for user to replace fuse at all.

http://www.cantherm.com/products/thermcut_reg.htm

http://www.cantherm.com/products/thermcut.htm

http://www.microtherm.co.uk/

http://www.globalspec.com/featuredp...Detectors/Temperature_Sensing/Thermal_Cutoffs

http://www.pepiusa.com/HOWTO/types2.html

RL

 

[Berge Duravin]

dated 12 Aug 2004 18:38:22 -0700,

Also, I am thinking of using components on my DC motor but not DEVICE.
Low cost and simple component is the best.

A Motor Protection Relay is low cost and simple component.

Maybe finally, I suppose to use a electronic circuit to behave as over
current cut-off which motor rotor locking.

A Motor Protection Relay is cheaper than your electronic circuit
wich you have to design.

You have already destroyed one motor, you are going to destroy more
motors and your electronic components will all lose their magic smoke.

You are a chinese and a dick head, it is a waste of time trying to
help dick-headed chinese.

 

[Rich Grise]

THANK YOU FOR YOUR REPLY.

I am quite interested in what you have mentioned about
"Motor Protection Relay".
Can you give me more detail on the regarding components?

I suppose to have as simple as possible solution on how to
prevent over-heat/ current on DC motor locking. And fuse is not
a good suggestion for me because it is only for 1 shot used.
Of course, it is not convenience for user to replace fuse at all.

Then there's something wrong with the basic design. What kind of
machine is it where the rotor locks so regularly? If it's part of
the normal operation of the machine, then you want to depend on
something besides motor overcurrent to cut off power.

If it's a fault condition, then you need to find out what's breaking
it. A self-resetting fuse, in this situation, will just ensure that
one day your factory burns down.

Good Luck!
Rich