Brushless vs. Brushed Tacho Generators: Pros, Cons, and Real-World Use Cases

Tacho generators remain the workhorse of analogue speed feedback—even as digital encoders grab most of the headlines. But not all tachos are built the same. One of the first choices you’ll face is brushed versus brushless construction. Below, we break down how each works, where each excels, and which industries lean one way or the other.

1. How They Work—At a Glance

2. Advantages & Disadvantages

Brushed Tacho Generators

Pros

• Lower purchase price—around 30 % below brushless equivalents.

• Higher output voltages possible without extra electronics; useful for long cable runs.

• Proven legacy compatibility with older DC drives that expect a specific K_T range.

Cons

• Brush wear means scheduled maintenance (typically every 3 000–6 000 hours).

• Brush dust can contaminate nearby electronics in clean rooms.

• Commutator ripple slightly higher, limiting servo bandwidth in high-precision loops.

Brushless Tacho Generators

Pros

• Zero brush maintenance—ideal for remote or difficult-to-access equipment.

• Lower electrical noise (no brush arcing), a plus in EMI-sensitive plants.

• Longer MTBF; fewer moving contact points equals fewer failure modes.

Cons

• Higher initial cost—especially for stainless, IP67 marine variants.

• Fixed voltage constant; boosting V_out often requires an external amplifier.

• Slightly larger envelope in some frame sizes due to stationary coil pack.

3. Performance & Maintenance Snapshot

*Illustrative figure for a 15 kW drive at UK 2025 costs; see our recent cost-of-ownership study for details.

4. Real-World Use Cases

A. Paper Mill Sectional Drives (Brushed Wins)

• Why: High-voltage (40 V / 1 000 rpm) brushed units can run 50 m of shielded cable without booster amps.

• Outcome: Every calender stack in a UK mill has run the same brushed tachos for 18+ years with quarterly brush swaps.

B. Offshore Wind Turbine Pitch Motors (Brushless Wins)

• Why: Climbing 100 m to change brushes is a non-starter. IP67 brushless tachos deliver zero-maintenance feedback despite salt spray and minus-20 °C gusts.

• Outcome: OEM logged four times fewer speed-loop alarms versus legacy encoders.

C. Servo-Controlled Extruders (Toss-Up)

• Scenario: 200 Hz bandwidth required.

• Choice: Brushless provides lower ripple for tighter PID tuning, but brushed remains viable if cost-pressure is high and a ripple filter is acceptable.

D. Micro-Hydro Plants in Remote Valleys (Brushless Wins)

• Why: Site visits involve 4×4 tracks and river crossings. Brush-free design slashes travel costs and downtime.

• Outcome: Community co-op hit 98.6 % availability over five years with zero sensor failures.

5. Decision Checklist

1. Access & Maintenance Budget

   • Hard-to-reach location? Go brushless.

2. Cable Distance & Voltage Drop

   • Need > 20 V over long runs? Brushed may be simpler.

3. Environmental Contaminants

   • Dust, sugar, or pharma powders? Brushless avoids airborne carbon.

4. Dynamic Response

   • Servo loop > 100 Hz? Brushless ripple advantage matters.

5. CapEx vs. OpEx

   • Brushed saves day-one cash; brushless wins on lifecycle cost.

Conclusion: Pick the Tool, Not the Trend

Brushless tachos dominate new renewable and high-precision builds, but brushed models still deliver unbeatable value for many industrial mainstays. Match the sensor to maintenance strategy, signal requirements, and environmental realities—and either type will repay you with years of reliable, linear speed feedback.

Need help choosing, sizing, or integrating a tacho generator? Our engineers are a quick call away and can quote both brushed and brushless options tailored to your application.