Precima fast excitation rectifier pmg500 & its applications
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The PMG fast excitation rectifier is recommended whenever short release time or low dissipation is required. It is also used for large size brakes (e.g. above 1000Nm) designed only to be released using overexcitation rectifiers.
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It combines the benefits of the half-way and bridge rectifiers.
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Upon supplying AC voltage, PMG500 provides full wave
rectification for the initial 500ms; and after which it switches automatically to half wave rectification for the rest of the period. - In order to switch back to full wave rectification for 500ms again, a re-supply of AC voltage is required every time
Application Example of Short Release Time
Supplied voltage: 400 VAC
Brake coil voltage: 180 VDC
- Optimum release of brake by overexcitation of the coil (release voltage 360 VDC for 500 ms)
- The allowed operating air gap will be expanded by a factor 2 (servicing intervals are increased)
Supplied voltage: 230 VAC
Brake coil voltage: 103 VDC
- Optimum release of brake by overexcitation of the coil (release voltage 207 VDC for 500 ms)
- The allowed operating air gap will be expanded by a factor 2 (servicing intervals are increased)
Application Example of Low Dissipation
Supplied voltage: 230 VAC
Brake coil voltage: 205 VDC
- Normal release of brake by overexcitation of the coil (release voltage 205 VDC for 500 ms)
- Cutting the intervention time of the brake by reducing the voltage to 103 VDC (such voltage is sufficient for securely holding the rotor disk)
- Reducing the electrical power to 25%
- Reduced heating of the brake