Hedges
I See Electromagnetic Fields!
- Joined
- Mar 28, 2020
- Messages
- 23,152
A stalled universal motor sees DC not AC in its windings, inductance would hold off the AC component of a step function when switch closed, but then current rises until limited by wire resistance.
A universal motor spins up until back EMF counters applied voltage.
Higher voltage, spins faster. Lower voltage, spins slower.
Ancient slot car or other toy motors were brush type, could be permanent magnet or wound field (universal.)
Your drones may have all been BLDC, 3-phase motors with inverter drive. So could change what you observe. Current limited to what FETs could handle by control electronics.
AC induction motors provide more torque with slight RPM slip below line (or VFD) frequency.
Split-phase induction motors have poor starting torque, depend on capacitor to give a bit of phase shift. (some technique to make them start without capacitors too.)
3-Phase motors get three 120 degree phases and have full torque from a standstill. Or higher, with full voltage and excessive current. VFD ramp them up with PWM limiting current while varying frequency.
Permanent magnet motors driven by VFD I think are locked to speed of driving frequency. Torque is angle between rotor and rotating magnetic field. VFD varies PWM as needed to limit current and achieve torque.
A universal motor spins up until back EMF counters applied voltage.
Higher voltage, spins faster. Lower voltage, spins slower.
Ancient slot car or other toy motors were brush type, could be permanent magnet or wound field (universal.)
Your drones may have all been BLDC, 3-phase motors with inverter drive. So could change what you observe. Current limited to what FETs could handle by control electronics.
AC induction motors provide more torque with slight RPM slip below line (or VFD) frequency.
Split-phase induction motors have poor starting torque, depend on capacitor to give a bit of phase shift. (some technique to make them start without capacitors too.)
3-Phase motors get three 120 degree phases and have full torque from a standstill. Or higher, with full voltage and excessive current. VFD ramp them up with PWM limiting current while varying frequency.
Permanent magnet motors driven by VFD I think are locked to speed of driving frequency. Torque is angle between rotor and rotating magnetic field. VFD varies PWM as needed to limit current and achieve torque.