4VM62-020-9 Pacific Scientific
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The Pacific Scientific 4VM62-020-9 is part of the Low Inertia PMDC Servomotors series and uses an Alnico V-7 magnet material. This servomotor features a standard analog tachometer with a voltage constant of 2.5 volts per kRPM and a resistance of 50 ohms at 25°C. It is designed without forced-air cooling and has a tach rotor inertia of 0.00005 oz-in-s^2.
Internal Product Review
The 4VM62-020-9 is a Pacific Scientific low inertia PMDC servomotor with a standard analog tachometer and no forced-air cooling. Alnico V-7 magnet construction and ±0.5% tach linearity support stable speed feedback and dependable servo response. A well-executed motor choice for applications that value clean tach performance.
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Product Description:
The 4VM62-020-9 is a permanent-magnet DC servomotor manufactured by Pacific Scientific as part of the Low Inertia PMDC Servomotors series. In automated machinery, this motor supplies low-inertia torque for precise velocity and position loops, allowing drive amplifiers to accelerate loads quickly and hold the commanded speed without overshoot. This model relies on convection because its housing has no forced-air cooling, so adequate airflow inside the enclosure is required to keep the frame within allowable temperatures.
Shaft torque is produced by a rotor that interacts with field poles made from Alnico V-7, a magnet material chosen for stable flux over a broad temperature range. The integral analog tachometer has a maximum outside diameter of 2.765 in and an overall length of 2.062 in; these dimensions establish the required clearance when the feedback device is installed near gearboxes or couplings. Electrical feedback accuracy is aided by tachometer linearity held to ±0.5% of its output, limiting speed-loop error when the drive uses raw tachometer voltage instead of a digital encoder.
The tachometer has an armature resistance of 50 Ω at 25 °C, a value that sets the current drawn from the drive’s sensing circuit and influences time-constant matching. Its rotor contributes only 0.00005 oz-in-s² of inertia, so the added sensor does not noticeably reduce system bandwidth. Voltage sensitivity is fixed at 2.5 V/kRPM, allowing controllers to calculate motor speed directly from the measured voltage without scaling networks. Output variation is limited to a maximum of 1.5% peak-to-peak ripple, helping maintain stable velocity estimates under light loads. A ±5% tolerance band applies to the voltage constant, and the motor does not include an optical encoder, providing analog feedback for applications where digital position resolution is unnecessary.
