driving my large coil

[Deleted]

Hi all, i have a large coil used to magnetize iron rods to analyze the efect of magnetic field on the iron rods..

the coil has an impedance of about 20Ohm and to make a suitable effect it is fed by a current from 0 to 60 A dc ( i.e. it is fed by voltage from 0 to 120Vdc)..
how to do such design ..

by chopper or SMPS or what...


thanx a lot... SHENDY

[Deleted]

Sorry for all.. the current from 0 to 6 Amp. not 60 A as i posted before...

[Gary Lecomte]

Hi Shendy, Impedance is AC related, Not DC.

Resistance is DC.

Probably the Best thing would be a Variac with the output of it, full wave Rectified and also Filtered with at least 10,000 uf of capacitance to remove most of the ripple.

Be Aware that Most Variacs put out 140 volts maximum.
When Rectified, this can result in an output of 1.41 times the RMS voltage, or about 196 Volts.
That will exceed your 6 amps in that coil. (to almost 10 Amps)
And if this is the case, you better make that 20,000 uf or more.

Also be aware that the ouput current after rectification is only 0.707 of the input current. And this doesn't take into account losses in filtering.

** You will probably need a Variac rated at about 10 to 12 amps to get the 120 volts at 6 amps of good DC power.
(Or at least a 15 amp variac if you plan to use the possible 196 volts.)

But I really don't see the point in what your doing?
Yes you can magnetize Iron, especially Iron with a high carbon content.
(Tool Steel)

[Deleted]

Dear Gary Lecomte.. first of all thank you very much for your interest..
i don't want to use variac, in my country it is expensive and very short life, in addition it is heavy ...

i want to use a chopper circuit that modulate a dc voltage of about 150 vdc with a variable duty cycle and load that coil.. but what is the best chopper circuit and what is the best chopper switch ( power BJT or power MOS or power IGBT ).. do i need a snubber circuit ? what is the recommended frequency of chopping? ..
by the way i succedded to drive smaller coil by a 555 chopper circuit and using a power transistor ..

thanx again for your interest..... Shendy

[Gary Lecomte]

There is No Best Frequency.

A 555 driving a mosfet will do it, but you need a mosfet with a quite high voltage.

This circuit can do it, but with a Higher Voltage Mosfet, at least 400 volt.
600 volts, even better.
Also use a bigger heatsink.
And a Snubber circuit would be a good idea also.

** Inductive kickback, creating high voltage spikes is your enemy.

www3.telus.net/chemelec/Projects/PWM/PWM.htm

Hopefully your 150 VDC is VERY WELL FILTERED.
If it is rectified AC, Than at Least 10,000 uF.
*****************************************************

mahmoud said:

Dear Gary Lecomte.. first of all thank you very much for your interest..
i don't want to use variac, in my country it is expensive and very short life, in addition it is heavy ...

i want to use a chopper circuit that modulate a dc voltage of about 150 vdc with a variable duty cycle and load that coil.. but what is the best chopper circuit and what is the best chopper switch ( power BJT or power MOS or power IGBT ).. do i need a snubber circuit ? what is the recommended frequency of chopping? ..
by the way i succedded to drive smaller coil by a 555 chopper circuit and using a power transistor ..

thanx again for your interest..... Shendy

[Deleted]

Dear Gary Lecomte..
I don't know how to thank you, thank you very very much.
thanx again....
M.Shendy