Credit: Michael Rosenblum and Ron Carroll
ONYX RCR Line Amps and Phase Amps
It’s great that Michael Rosenblum, Ron Carroll, and I are breaking down the real-world power flow to better understand how much performance an ONYX is truly capable of. We’re right that marketing numbers often don’t reflect how power is actually utilized in a system.
Relating key mechanical and electrical units to their corresponding physical effects.
Let’s break it down:
- Kw = hp
- Pa = Torque
- V = speed
Another Example
- KW (Kilowatts) = Horse Power
- PA (Pascal) = Torque (indirectly)
- V (Volts) = Speed (indirectly)
Using the formulas kW = HP, Pa = Torque, and V = Speed gives a broader mechanical understanding and connects directly to the ONYX performance in terms of power, torque, and speed, which is useful for practical applications like tuning or optimizing.
kW (Kilowatts) = HP (Horsepower)
- The relationship between kilowatts and horsepower is: 1 kW = 1.341 HP
- So if you know the power in kilowatts, you can convert it to horsepower by multiplying by 1.341.
- Example: A motor producing 3 kW would deliver about 4.02 HP.
Pa (Pascal) = Torque (indirectly)
- Torque is often expressed in Newton-meters (Nm), but pressure (in Pascals, Pa) relates to force over an area.
- The formula for torque is: Torque = Force × Lever arm length
- In certain hydraulic systems, pressure (Pa) can generate torque if it applies force through an actuator over a distance.
V (Volts) = Speed (indirectly)
- In electric motors, voltage is related to speed in that higher voltage typically results in a higher motor speed, assuming a constant load. For a given motor: Speed (rpm) ∝ Voltage
- More voltage allows the motor to spin faster, increasing speed, especially in systems like an e-bike where the motor speed directly correlates with wheel speed.
In Summary
- Power (kW) determines the capacity to do work, often equated to horsepower in engines.
- Torque (Nm or Pa-related) is the twisting force that enables acceleration or climbing.
- Voltage (V) influences the speed of the motor or e-bike.
These relationships are crucial when tuning e-bikes for either top speed (higher voltage) or better torque and acceleration (higher current or phase current).
Clear Summary Of The Process
Battery to Controller (DC)
- The power starts as direct current (DC) from the battery. This is what limits the maximum voltage and amps that the system can draw, depending on the battery’s capacity.
- Controller to Motor (AC):
- The controller converts the DC power into alternating current (AC) to power the motor. While it’s a 3-phase motor, only two phases are active at any given time, and the controller switches between them to drive the motor efficiently.
6-Phase Motors (Hub Monster example)
- Older designs like the Hub Monster used a 6-phase setup requiring two controllers, where four phases would be active at a time. This allowed for smoother power delivery but required more complex electronics.
ONYX RCR Power Management
- The stock ONYX RCR is an interesting case because its 50A limit means it’s not pushing anywhere near its actual capabilities. This limitation results in better longevity and reliability but leaves a lot of performance untapped. When fully pinned in sports mode, it’s only using about one-third of the bike’s potential.
ONYX bikes are over-engineered to last, rather than push the limits constantly. It also leaves room for customization or tuning for those who want to unlock more power.
A three-phase motor is like a spinning magnet that makes things move. It has three wires that take turns pushing the motor, making it turn smoothly.
Now, let’s talk about the 72-volt system with 200 amps and 100 amps. Think of the 72 volts as the full power the motor can get when it’s going super fast. But when you’re at the starting line and press the throttle (gas), the motor doesn’t get all that power right away. It has to “wake up” and start moving first.
At the beginning, the controller (which controls how much power goes to the motor) gives the motor 200 amps of electricity. But since the motor isn’t moving yet, it only gets a little bit of the 72 volts. As the motor starts to spin and go faster, the volts start to rise. The faster it spins, the closer it gets to using all 72 volts.
So, at the start, the motor gets a lot of amps to give it a big push, but it takes time for it to get all the volts. The line amps (100 amps DC) is the amount of electricity the battery is giving, while the 200 amps AC is what’s actually going to the motor’s spinning parts to get it moving.
In short: You give the motor a big push (200 amps AC) to start it moving, and as it speeds up, it gets more and more power (volts) to go even faster!
Kelly KLS7230S Controller
- KLS7230S
- 72 Volts
- 300 Amps
- Standard Body
- Waterproof
- Field Weakening
- Waterproof Connector
- Bluetooth Adapter
Kelly KLS7230S Controller Specifications
- Motor Phase AC Current Limit, continuous: 120A.
- 72 x 120 x 2 = 17.2kw Continous.
- Motor Phase AC Current Limit, 10 seconds boost: 300A.
- Boost is 4.4kw extra AC power delivery for 10 seconds.
I’m describing converting DC power from the battery into AC power for a three-phase motor on an ONYX. The controller takes the DC voltage from the battery and converts it into AC by switching between phases, typically in a six-step (or trapezoidal) sequence. The galloping fingers analogy matches the way the controller energizes the motor’s windings in a sequence (1, 1-2, 2, 2-3, 3-1, 1). This sequence creates a rotating magnetic field that drives the motor.
In my example of 72V nominal and 100A of line DC, the phase current at the motor side increases because of the switching process, often by a factor of √3. Thus, the line current of 100A DC could produce up to 200A AC in the phases. The total power output in kilowatts (kW) would indeed be ( P = V \times I = 72 , \text{V} \times 100 , \text{A} = 7.2 , \text{kW} ) at the DC side, but at the motor side, with phase currents up to 200A, you’d see 14.4kW at full load.
The relationship between line current and phase current is also impacted by motor efficiency and controller characteristics, but the fundamental idea is correct.
To explain a three-phase motor system and how the current and voltage behave, here’s a simple way you could break it down:
First, let them know that a three-phase motor has three wires (phases) that deliver power in a rotating sequence, creating a magnetic field that turns the motor. This is efficient for generating torque.
Now, onto the 72-volt system with 200 amps AC phase and 100 line amps:
The 72 volts represents the maximum voltage the system can reach when the motor is running at full speed. The motor doesn’t instantly get this voltage; it needs to “ramp up” as you apply throttle and the motor spins faster.
When you’re at rest, and you apply throttle, the controller will send 200 amps AC of current to the motor’s windings (AC phase amps). However, because the motor is just starting and isn’t spinning yet, the voltage it “sees” is low. The motor needs to start turning, and as it does, the voltage increases with the motor’s speed.
The key point is that the current (amps) at low speed is what helps create the initial torque to get the motor moving. But the voltage (72 volts) gradually builds as the motor spins faster. It’s only at full speed that the system will reach close to 72 volts. The line amps DC (100 amps) is the current drawn from the battery, which is different from the phase AC current (200 amps) because the motor’s controller converts voltage and current to optimize performance.
So, when you’re at the starting line, the system is pushing 200 amps into the motor, but it takes time for the motor to speed up and reach the full 72 volts.