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Important One Liner (Testing of DC Machine)
- The Swinburne test predicts DC machine efficiency using no-load and blocked-rotor measurements.
- The Hopkinson test compares losses by coupling two identical machines back-to-back under load.
- Brake test directly measures mechanical output using a dynamometer for accurate efficiency.
- Field test determines field winding resistance by measuring voltage and current under controlled conditions.
- Blocked-rotor test measures armature copper losses with rotor locked at zero speed.
- Swinburne test assumes stray losses constant for all loads when calculating performance.
- Hopkinson test requires two identical machines, increasing setup cost and complexity.
- Brake test is preferred for large machines due to direct measurement of torque and speed.
- Field test provides insights into armature reaction and demagnetizing effects on performance.
- Swinburne test is unsuitable for machines with significant mechanical losses at load.
- Hopkinson test yields accurate efficiency curves for full-load and overload conditions.
- Brake test demands precise calibration of dynamometer for reliable output power readings.
- Field test data helps in adjusting field excitation to improve voltage regulation.
- Blocked-rotor losses include both copper and frictional components at standstill.
- Swinburne method is ideal for routine testing of small DC machines in workshops.
- Hopkinson setup includes coupling shaft alignment to minimize vibration and losses.
- Brake test can be hydraulic, mechanical, or electrical depending on dynamometer type.
- Field test can also reveal insulation defects under different excitation currents.
- Blocked-rotor current inversely relates to field strength for DC machines.
- Comprehensive testing ensures reliable DC machine performance under varying load conditions.
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