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Lynch motors have continuous ratings of 200A or less, they will stand peaks for a few seconds only at up to 400A, but it is not desirable to rely on running at these currents. We have used 400A & 350A controllers in cars but have turned them down to 275-350A to avoid risk of motor overheating and failure. We are still experimenting with optimum current settings for cars weighing 900-1000Kg, eg Ford Fiesta - if too low, car won't climb kerbs or steep ramps!

The above suggests that for cars we have at present, using a single Lynch motor, we need a true continuous rating of 90-100A with peak of 275-300A for a few seconds.

We are actively considering higher power motors – as in the double-armature version - the `power' being primarily to provide torque at reasonable speeds for hill- or ramp-climbing. (Using a 4:1 gearbox, as in Fiesta, the standard 60V 10.5 KW motor has adequate torque, but it may be too slow for traffic stream (eg 10mph in bottom gear for car geared for 40mph in top gear).

Additional power/torque can be obtained (a) by running two 10.5 KW armatures on one spindle to give 21KW - either in series (120V 200A max) or parallel (60V 400A) or combination of both by series-parallelling as on some of our vehicles where a wider speed range is required - or (b) by developing a larger motor of the same power (c. 20KW) as we are doing at present - target parameters: weight < 20Kg, Dia about 250mm running on higher voltages (say 120V). For certain applications it may be better to limit EMF to 48V and 96V.

The requirement for boats is different. The peak power is generally lower than for cars but the duration is much longer - they therefore require a true continuous rating. We find that Curtis controllers start to cut back at about 25% of peak current. When running continuously – good heat sinking, with water or air cooling, is essential.

DESIRABLE FEATURES
(Priorities in brackets - desirable but not necessarily achievable yet!)

1. Peak and Continuous ratings to be accurately stated. (1)
2. High frequency - well above audio limit for higher efficiency - say 25KHz. (1)
3. Motor Current limit adjustable down to below 20% of max.(1) - against temp, and against time,
when overload reached (2)
4. Battery Current Limit (1)
5. Regeneration, but reverse not necessary - 2 Quadrant. (2)
6. Must not short if supply cut off, ie inherently safe. (1)
7. Battery charging (3)
8. Float voltage for auxiliaries - say 13.5V capable of charging batteries, 20-30A max? (3)

CONTROL
1. Adjustable delay down to zero (1), and adjustable shape of throttle ramp. (2)
2. Input control 0-5KOhm with option of 0-5 Volts; fail-safe protection against runaway on
open circuit. (1)
3. High Pedal Detect - ie not to start on open `throttle'. (1)
4. Alternative 3-wire pot connection (1) giving smooth acceleration and switched reversing option
with potentiometer centre-tap (5-0-5 K).
5. One controller to cover as wide a voltage range as possible, but with adjustable battery protection -
ie minimum voltage can be set to 10.5-11V per 12V battery. To trigger relays at 75% and 80%
depth of dischage. (2)
6. Battery state of charge indication. (3)

ADDITIONAL FEATURES
1. Current limits etc to be readily adjustable from driving position eg through separate terminals
connected to external controls, rather than trimmers built into circuit board. But must also be
capable of being locked/pre-set, where required.
2. The driving control should have the option of being through (a) motor current limit (b) battery
current limit (c) output voltage (as with present Curtis - best for low-speed manoeuvering).

RELAYS AND RELAY DRIVERS
1. Timer Relay Driver: Signals that the motor load is above 105% and that the stall timer is
operational. Used to drive an external signal relay. (2)

DRIVE ALARMS, PROTECTION AND INDICATORS
1. Drive Healthy Output: Relay drive signal to show that drive is ready to go. (2)
2. Motor Temperature Alarm: Immediate latched drive shutdown in the event of motor over
temperature. LED indication. (2)
3. Overspeed Limit: Speed reference inputs remain active when operating in torque mode, thus
allowing control of the overspeed limit. (2)
4. Stall Timer warning: Signal output warns that the motor load is above 105% and that the stall
timer is operating. LED indication. (2)
5. Stall Lamp: Indicates that the internal drive trip has operated to protect the motor due to
excessive load or incorrect calibration. (3)

SPEED CONTROL FEATURES
1. S Shaped Ramps Facility: Allows the speed demand ramp to have a soft profile at start and end of
speed change. (3)
2. Armature Voltage Feedback: Built-in feature provides cost-free alternative to tachogenerator. (2)

 

 
         
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