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Which MOSFET / IGBT can afford 5A current normal operation and 40A current at 1-2 seconds?

F

Fritz Schlunder

Jan 1, 1970
0
Electronic Swear said:
The DC motor is operated at (rectified) 220Vac.
It is for food juicer. We don't want to use current
sensing because the motor start-up current is very large.
Similiar to what the current at lock rotor. As a result,
current monitoring is not a very good method. Even the motor
will be over-loading for a short moment when the user is putting
a very hard / big food for juicing at the beginning.
The current will be very large at the beginning but will drop
to a suitable value. However, we cannot cut-off the motor source
because of over-current. We will allow the motor operating at a
very high current for a short time, several seconds.

The motor is for masss production and look for safety protection
as well. If use fuse on protection, it is very inconvenient for
exchange. We want some active protection rather than passive components.

I will try for using the SCRs at the bridge rectifying.
However, the current rating of the SCR just 25A is enough or not?
And any detail on snubber capacitor?


Hmm... Mass production... DC motor from rectified 220Vac... Food
juicer... 40A for two seconds overload current...

Is this a consumer product?

I live in a 120Vac country, but allot of household circuits have circuit
breakers of only 15Amps or sometimes 25A. I imagine in 220Vac countries
they would use similar or smaller circuit breakers. If this is a consumer
product I should imagine if you let the motor draw 40A for two seconds in
allot of instances it will trip the household circuit breaker... Am I
missing something here?
 
W

Winfield Hill

Jan 1, 1970
0
Fritz Schlunder wrote...
If this is a consumer product I should imagine if you let the
motor draw 40A for two seconds in a lot of instances it will
trip the household circuit breaker...

Perhaps it isn't at 40A for the entire 2 seconds... Or...
Hmm, if the machine is straining, wihch the user can tell,
I think 2 seconds is a rather long time... Try it out.
 
W

Winfield Hill

Jan 1, 1970
0
Electronic Swear wrote...
The DC motor is operated at (rectified) 220Vac. It is for food
juicer. We don't want to use current sensing because the motor
start-up current is very large. Similiar to what the current at
lock rotor. As a result, current monitoring is not a very good
method.

Why not use current sensing and let the processor decide when the
special case of a startup means forgiving high current a little
longer?
the motor will be over-loading for a short moment when the user
is putting a very hard / big food for juicing at the beginning.

Another case the microprocessor can detect.
I will try for using the SCRs at the bridge rectifying. However,
the current rating of the SCR just 25A is enough or not?

Each SCR works at 50% duty cycle. Study the datasheets.
And any detail on snubber capacitor?

It's past time for you to start reading the links we've provided
and learning about the scene.
 
N

Nico Coesel

Jan 1, 1970
0
The DC motor is operated at (rectified) 220Vac.
It is for food juicer. We don't want to use current
sensing because the motor start-up current is very large.
The motor is for masss production and look for safety protection
as well. If use fuse on protection, it is very inconvenient for
exchange. We want some active protection rather than passive components.

Sorry, but the way I see it, current sensing is even better. Like I
typed before, it will give you a soft start and longer switch life for
free, it will provide better protection against fire (a stall detector
is always off board) and it will cost less.
 
W

Winfield Hill

Jan 1, 1970
0
Winfield Hill wrote...
Electronic Swear wrote...

Why not use current sensing and let the processor decide when the
special case of a startup means forgiving high current a little
longer?


Another case the microprocessor can detect.

Plus, you can use the SCRs with phase control to reduce the current
during stall, to avoid requiring shutoff entirely, unless the stall
condition lasts far too long. You could also create a "stutter" in
an attempt to free up the stall, and to send a signal to the user.
You can list me on the patent applications. :<) Or just send money.
 
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