DIY Electric Car Forums banner
1 - 11 of 11 Posts

·
Registered
Joined
·
44 Posts
Discussion Starter · #1 · (Edited)
Hi Guys, I've been thinking too much again perhaps but I believe that the internal wiring for the 2 pairs of brushes and the 2 pairs of field coils are each separately parallel to their respective terminal posts, if this was all connected in series then wouldn't this mean a 500A 288V would be equivalent to the 1000A at 144 volt controller, any ideas on this concept? More importantly it would allow 288-300v controller with 1000A capabilities to output massive motor torque equivalent to a 2000A controller at the old 144-150v bracket. Of course just for crazy fast acceleration briefly.
 

·
Registered
Joined
·
7,977 Posts
No, the rotor or armature (via the brushes and commutator) and the stator or field are in series.

Even if you start with a different motor that has them in parallel (a shunt or separately excited field - "SepEx" - type), you can't just connect them in series because in those motors the field winding is designed for much less current than the rotor winding.
 

·
Administrator
Joined
·
6,443 Posts
Its a series motor - the current goes through the armature then the field coil

Remember the voltage and the current are dependent on each other

For any given rpm and current there is ONE voltage that will achieve that - the controller takes the battery voltage and reduces it to the correct voltage for the motor

Rough numbers - for illustration
Zero rpm --- 1000 amps motor ---- 15v motor ==== 150v battery and 100 amps battery
1000 rpm --- 1000 amps motor ---- 45 volts motor ==== 150v battery and 300 amps battery
2000 rpm --- 1000 amps motor ---- 80 volts motor ==== 150v battery and 533 amps battery
3000 rpm --- 1000 amps motor ---- 110 volts motor ==== 150v battery and 733 amps battery
4000 rpm --- 1000 amps motor ---- 140 volts motor ==== 150v battery and 933 amps battery
5000 rpm --- 800 amps motor ---- 150 volts motor ====150v battery and 800 amps battery
6000 rpm --- 600 amps motor ---- 150 volts motor ====150v battery and 600 amps battery
 

·
Registered
Joined
·
7,977 Posts
For any given rpm and current there is ONE voltage that will achieve that - the controller takes the battery voltage and reduces it to the correct voltage for the motor
Well said :)

The required motor output torque determines the current required to produce the corresponding magnetic force. The motor speed and the current in the windings determines the voltage required to overcome back-EMF (the voltage induced in the motor's windings due to the changing magnetic field). The current in the windings and the resistance of windings determines the voltage required to overcome resistance.

Remember the voltage and the current are dependent on each other

Rough numbers - for illustration
Zero rpm --- 1000 amps motor ---- 15v motor ==== 150v battery and 100 amps battery
1000 rpm --- 1000 amps motor ---- 45 volts motor ==== 150v battery and 300 amps battery
2000 rpm --- 1000 amps motor ---- 80 volts motor ==== 150v battery and 533 amps battery
3000 rpm --- 1000 amps motor ---- 110 volts motor ==== 150v battery and 733 amps battery
4000 rpm --- 1000 amps motor ---- 140 volts motor ==== 150v battery and 933 amps battery
5000 rpm --- 800 amps motor ---- 150 volts motor ====150v battery and 800 amps battery
6000 rpm --- 600 amps motor ---- 150 volts motor ====150v battery and 600 amps battery
In this example, the system of battery, controller, and motor is limited to 1000 amps by the controller, so at lower speeds that's the maximum current. At zero speed, 15 volts is required to overcome resistance.
As the speed increases, back-EMF increases so more voltage is required to sustain the same current.
After 4000 RPM all of the available voltage from the battery is needed to overcome back-EMF, so higher speed means less voltage remaining to overcome resistance, and so less current; with the same voltage and less current, power drops.

The controller "trades" voltage for current, and can't increase voltage, so it takes as much current from the battery as required to get enough power. Voltage from the battery multiplied by current from the battery is the power provided by the battery; voltage to the motor multiplied by current through the motor is the power supplied to the motor. The battery power will be more than the motor power, due to less than perfect controller efficiency.
 

·
Registered
Joined
·
44 Posts
Discussion Starter · #6 ·
No, the rotor or armature (via the brushes and commutator) and the stator or field are in series.

Even if you start with a different motor that has them in parallel (a shunt or separately excited field - "SepEx" - type), you can't just connect them in series because in those motors the field winding is designed for much less current than the rotor winding.
Hi Brian, I think I might not have explained myself very well. What I'm talking about here is that inside the warp9 the two pairs of brushes are connected to the external brush terminal posts in parallel (not in relation to the field posts).. the same for the two pairs of field poles they are in parallel with the field terminal posts. (Not in relation to the brushes terminal posts).

Then "externally" we run these two sets of connections in series. I do understand that the motor is called a series wound motor due to it being connected with its brushes and field terminals all in series with each other in the visible cable circuit to the controller.

So what I'm suggesting is:

The 4 field poles all connected inside the motor in series rather than parallel.

Then connected in series to the brushes and those 4 brushes also connected internally with each other in series rather than in parallel. And finally back to the controller circuit.

The idea behind this is that it would half the "current capacity" of the motor but at double the voltage without reducing the torque provided. Plus for temporary acceleration burst you could use 1000A at 288V and the motor sees only the same voltage at each brush contact as the normal configuration (at 144V) but you now have the equivalent of running a 144v controller with a 2,000A peak current for launching hard off the line.

Of course the idea is that this would also mean at regular cruise conditions your only running rather low battery current draw at the high system voltage. Potentially better overall efficiency etc etc. But with the ability to very very briefly push 288-300kW through a Single warP9 motor with a Soliton1.
 

·
Registered
Joined
·
44 Posts
Discussion Starter · #7 ·
Its a series motor - the current goes through the armature then the field coil

Remember the voltage and the current are dependent on each other

For any given rpm and current there is ONE voltage that will achieve that - the controller takes the battery voltage and reduces it to the correct voltage for the motor

Rough numbers - for illustration
Zero rpm --- 1000 amps motor ---- 15v motor ==== 150v battery and 100 amps battery
1000 rpm --- 1000 amps motor ---- 45 volts motor ==== 150v battery and 300 amps battery
2000 rpm --- 1000 amps motor ---- 80 volts motor ==== 150v battery and 533 amps battery
3000 rpm --- 1000 amps motor ---- 110 volts motor ==== 150v battery and 733 amps battery
4000 rpm --- 1000 amps motor ---- 140 volts motor ==== 150v battery and 933 amps battery
5000 rpm --- 800 amps motor ---- 150 volts motor ====150v battery and 800 amps battery
6000 rpm --- 600 amps motor ---- 150 volts motor ====150v battery and 600 amps battery
Hi Duncan, thanks for your great technical reply. Love the voltage/current breakdown. I poorly explained my theory im sorry.

What I'm talking about here is that inside the warp9 the two pairs of brushes are connected to the external brush terminal posts in parallel (not in relation to the field posts).. the same for the two pairs of field poles they are in parallel with the field terminal posts. (Not in relation to the brushes terminal posts).

Then "externally" we run these two sets of connections in series. I do understand that the motor is called a series wound motor due to it being connected with its brushes and field terminals all in series with each other in the visible cable circuit to the controller.

So what I'm suggesting is:

The 4 field poles all connected inside the motor in series rather than parallel.

Then connected in series to the brushes and those 4 brushes also connected internally with each other in series rather than in parallel. And finally back to the controller circuit.

The idea behind this is that it would half the "current capacity" of the motor but at double the voltage without reducing the torque provided. Plus for temporary acceleration burst you could use 1000A at 288V and the motor sees only the same voltage at each brush contact as the normal configuration (at 144V) but you now have the equivalent of running a 144v controller with a 2,000A peak current for launching hard off the line.

Of course the idea is that this would also mean at regular cruise conditions your only running rather low battery current draw at the high system voltage. Potentially better overall efficiency etc etc. But with the ability to very very briefly push 288-300kW through a Single warP9 motor with a Soliton1.
 

·
Registered
Joined
·
7,791 Posts
Hi Duncan, thanks for your great technical reply. Love the voltage/current breakdown. I poorly explained my theory im sorry.

What I'm talking about here is that inside the warp9 the two pairs of brushes are connected to the external brush terminal posts in parallel (not in relation to the field posts).. the same for the two pairs of field poles they are in parallel with the field terminal posts. (Not in relation to the brushes terminal posts).

Then "externally" we run these two sets of connections in series. I do understand that the motor is called a series wound motor due to it being connected with its brushes and field terminals all in series with each other in the visible cable circuit to the controller.

So what I'm suggesting is:

The 4 field poles all connected inside the motor in series rather than parallel.

Then connected in series to the brushes and those 4 brushes also connected internally with each other in series rather than in parallel. And finally back to the controller circuit.

The idea behind this is that it would half the "current capacity" of the motor but at double the voltage without reducing the torque provided. Plus for temporary acceleration burst you could use 1000A at 288V and the motor sees only the same voltage at each brush contact as the normal configuration (at 144V) but you now have the equivalent of running a 144v controller with a 2,000A peak current for launching hard off the line.

Of course the idea is that this would also mean at regular cruise conditions your only running rather low battery current draw at the high system voltage. Potentially better overall efficiency etc etc. But with the ability to very very briefly push 288-300kW through a Single warP9 motor with a Soliton1.
Hi dkubus,

You're missing the armature winding configuration. It is a 4 pole wave wound circuit meaning it has two circuits, in parallel. It's connected to a 49 segment comm. Each armature coil (there are 49 with one turn each) is connected to segments 180° apart. This coil is in the neutral zone so essentially has no generated voltage while undergoing commutation (touching brushes and having current reversed). So, what that boils down to is that the brushes at 180° are a common node. In fact, the motor can operate with just 2 of the 4 brush sets at 90° yielding the same performance only derated due to less brush area.

Regards,
major
 

·
Registered
Joined
·
44 Posts
Discussion Starter · #9 ·
Thanks Major, I appreciate the explanation. I was under the impression that the two pairs of dual brush positions angled at 90 degrees to one another were connected in parallel with the other two brush sets (hence the ability to still operate on just two 90 degree separated brushes). Ignoring this handy fail safe ability for a moment, if connected alternatively (with respect to original brush pair polarity) in series with the A1 and A2 posts then I'd expect that if any brush fails the whole show stops. If not broken however the armature would have double the emf at the equivalent rpm of the conventional motor configuration. The benefits im thinking might exist are: most of the time while cruising at a particular power level the current in the motor supply will be half whilst voltage is doubled. (Internal motor current and voltage per brush and per winding is the same as conventional for any given kW levelof operation) but if you short burst accelerate (Soliton1) then you have upto 1000A that would in fact translate to equivalent standing start torque of a 2000A controller running at half the battry voltage.

Seeing as how 2000A controllers are rare and expensive i was thinking this is therefore a better utilisation of the high voltage input abilities of the soliton1 and would maximise take off torque without needing to fit my second warp9 (saving 80+ kg). Weight is the enemy of hillclimb racing.

Cheers for putting up with me.
Kind regards
Mike.
 

·
Registered
Joined
·
7,791 Posts
Thanks Major, I appreciate the explanation. I was under the impression that the two pairs of dual brush positions angled at 90 degrees to one another were connected in parallel with the other two brush sets (hence the ability to still operate on just two 90 degree separated brushes). Ignoring this handy fail safe ability for a moment, if connected alternatively (with respect to original brush pair polarity) in series with the A1 and A2 posts then I'd expect that if any brush fails the whole show stops. If not broken however the armature would have double the emf at the equivalent rpm of the conventional motor configuration. The benefits im thinking might exist are: most of the time while cruising at a particular power level the current in the motor supply will be half whilst voltage is doubled. (Internal motor current and voltage per brush and per winding is the same as conventional for any given kW levelof operation) but if you short burst accelerate (Soliton1) then you have upto 1000A that would in fact translate to equivalent standing start torque of a 2000A controller running at half the battry voltage.

Seeing as how 2000A controllers are rare and expensive i was thinking this is therefore a better utilisation of the high voltage input abilities of the soliton1 and would maximise take off torque without needing to fit my second warp9 (saving 80+ kg). Weight is the enemy of hillclimb racing.

Cheers for putting up with me.
Kind regards
Mike.
Hi Mike,

Sorry, cannot follow your logic. But your conclusion is wrong. You will not better performance by messing with the brushes. Google and study "dc motor wave wound armature", without quotes. Here's a linky.
Wave Winding | Electrical Study App by SARU TECH
Regards,
major
 

·
Registered
Joined
·
44 Posts
Discussion Starter · #11 ·
Hi Mike,

Sorry, cannot follow your logic. But your conclusion is wrong. You will not better performance by messing with the brushes. Google and study "dc motor wave wound armature", without quotes. Here's a linky.
Wave Winding | Electrical Study App by SARU TECH
Regards,
major
Thanks for setting me straight on this Major, sincerely appreciate it. This is what I've been trying to research for a while now but didn't know the terminology to search for. As always reading your descriptions and following the link you gave has clearly identified my mistake with my optimistic brain fart. Cheers mate.
 
1 - 11 of 11 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top