How Morgan Chopper does work?
In this post let us discuss about Morgan chopper in detail. It is good to refresh about chopper basics and Chopper types. Please click here to understand the basics of the Chopper and principle of chopper...
- The Morgan Chopper circuit uses the forced commutation technique.
- As shown in the figure, it has three SCRs. The SCR1 is the main SCR. The SCR-2 and SCR-3 are two auxiliary SCRs used for the commutation of the main SCR.
- The Inductor L and Capacitor C are the commutation elements which decide the time of commutation.
- First auxiliary SCR-2 is triggered which allows capacitor C to get charged with polarities as shown in above figure.
- The charging current will decrease when the capacitor C charge increases .
- When the capacitor achieves it full charge, the charging current stops flowing. Consequently SCR2 will be turned OFF .
- Now the capacitor is fully charged. It remains its charge as SCRs 1 and 3 in oFF position.
- When SCR-1 and SCR-3 are triggered simultaneously, capacitor C immediately starts discharging through L, SCR-1, SCR-3 and back to the negative plate of C.
- Since the discharge current is oscillating in nature, after its positive alternation it will change its direction of flow.
- Thus the polarities of capacitor C will reverse. Now, the upper plate will become negative and the lower plate will acquire positive charge.
- This will introduce reverse biasing for the SCRs 1 and 3 and therefore they are turned OFF.
- After a fixed period, SCR2 is again triggered and the above steps are repeated in the same sequence.
This type of chopper circuit assures better commutation and has better performance for lower values of chopper frequencies.
Disadvantages of the Morgan Chopper
- It requires three SCRs, thus one extra SCR for the commutation purpose.
- The main SCR has to carry the commutation current.
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