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Design a lock rotor protection circuit for high voltage high current DC motor

G

GoGo~

Jan 1, 1970
0
I have a 240Vdc DC motor with normal working current is 4A. For the
motor's rotor locking, its current will drive to 40A. So, I suppose to
design a external circuit for regarding motor.

It is a lock rotor circuit: when motor has been locked, the external
circuit can be detected the motor's rotor. If it is rotor locking, the
main input source will be cut off.

May I know how to design such kind of circuit? Because it is in high
voltage high current, is it not easy to use some voltage comparators
for current sensing? Any detail information can be shared?

Thanks~
 
F

Frithiof Andreas Jensen

Jan 1, 1970
0
May I know how to design such kind of circuit? Because it is in high
voltage high current, is it not easy to use some voltage comparators
for current sensing? Any detail information can be shared?

Do *not* waste time on it: It has already been done and done well!

The standard device is a "Motor Protection Relay", they are cheaper than you
can buy the components for - and there is much more to the story than mere
current for which a fuse would suffice; the current over time, the phase
realationship and the heat capacity of the motor is factored in too.

http://www.ab.com/industrialcontrols/products/supplemental_motor_protection/index.html

and (yikes!):

http://www.abb.com/global/abbzh/abb...e=us&m=9F2&c=BC8BA5A2FBD80967C1256DAA0044A679

and:

http://www2.automation.siemens.com/cd/is_schuetzen/html_76/ueberlastrelais.htm
 
G

GoGo~

Jan 1, 1970
0
Thnak you for your reply.
However, I want to build a external PCBA for it as I don't want to use
such large size stuff!!!

I want to use a voltage comparator to do something. But it is in low
voltage components. How can I convert such 240Vac to 12Vdc voltage to
drive the IC and triggering the IGBT for output controlling?

I think transformer that are not suitable for my application. Use
resistor series?
 
R

R Adsett

Jan 1, 1970
0
Thnak you for your reply.
However, I want to build a external PCBA for it as I don't want to use
such large size stuff!!!

I want to use a voltage comparator to do something. But it is in low
voltage components. How can I convert such 240Vac to 12Vdc voltage to
drive the IC and triggering the IGBT for output controlling?

I think transformer that are not suitable for my application. Use
resistor series?

One of Allegros hall effect Current Sensors?

http://www.allegromicro.com/hall/currentsensor.asp

Robert
 
D

Dave

Jan 1, 1970
0
GoGo~ said:
I have a 240Vdc DC motor with normal working current is 4A. For
the motor's rotor locking, its current will drive to 40A. So, I
suppose to design a external circuit for regarding motor. [...]

Hell, isn't that called a 6A circuit breaker?
 
GoGo~ said:
Thnak you for your reply.
However, I want to build a external PCBA for it as I don't want to use
such large size stuff!!!

then use a fuse... trying to rememebr the term for motor slow blow
ones.

I want to use a voltage comparator to do something. But it is in low
voltage components. How can I convert such 240Vac to 12Vdc voltage to
drive the IC and triggering the IGBT for output controlling?

I think transformer that are not suitable for my application. Use
resistor series?

yup, dont need any of that with a fuse tho. Or if you want it
resettable, a polywhatnot fuse. Or a cheap thermal mcb.


NT
 
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