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US 4,069,445 AGranted
Bypass control for a solid state switching device
AssigneeTowmotor Corporation
InventorRobert G. Klimo
Life of this patent
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AssigneeTowmotor Corporation
InventorRobert G. Klimo
Estimating the term…
A bypass control for shorting out a silicon controlled rectifier (SCR) control circuit so that full battery potential can be applied to a direct current motor. The bypass control has a timing circuit for delaying closing of the bypass contacts. This timing circuit is disabled in the event the main SCR is defective and will not turn on, and also in the event the motor is plugging. In the event the bypass contacts weld closed, the control will prevent further operation of the motor.
In a system for controlling the power delivered from a source of direct current to a load including a silicon controlled rectifier connected in series with said source of direct current and said load, a pulse generator for repeatedly gating the silicon controlled rectifier into conduction at a controlled rate, a commutation circuit for commutating the silicon controlled rectifier at a controlled time after the silicon controlled rectifier is gated into conduction, a by-pass relay having main contacts for connecting said load directly to said source of direct current when said relay is energized, the improvement comprising:
In a system for controlling the power delivered from a source of direct current to a motor having a field and an armature including a silicon controlled rectifier connected in series with said source of direct current and said load, a pulse generator for repeatedly gating said silicon controlled rectifier into conduction at a controlled rate, a commutation circuit for commutating the silicon controlled rectifier at a controlled time after the silicon controlled rectifier is gated into conduction, a bypass relay having main contacts for connecting said motor directly to said source of direct current, a direction relay having main contacts for connecting said field to said armature, and an energizing circuit for said direction relay, the improvement comprising:
Dependencies are inferred from the claim text.
No related US applications are recorded in the indexed filing history.
Drawings are temporarily unavailable. Open the PDF at USPTO
For electric motors with control arrangements: with H-bridge circuit
Emergency protective circuit arrangements
Term ended 17 Jan 1995 (estimated)
USPTO file history isn’t available for this patent, so only indexed dates are shown.
This invention is related to a control for direct current motors utilizing silicon controlled rectifiers (SCR's) to supply power to the motor and in particular to a circuit for bypassing the SCR control so that full battery potential may be applied to the motor.
It is well known that the direct current supplied to a motor from a constant potential power source such as a battery may be selectively varied by controlling the average power supplied to the motor, and that a solid state SCR can be used as a switching device to repeatedly connect and disconnect the battery to and from the motor. The power supplied to the motor is determined by a ratio between the time the SCR is turned on and conducts and the time that the SCR is turned off and is non-conducting.
Increasing the ratio of on-time to off-time will increase the power delivered through the SCR to the motor. However, even if this ratio is maximum, i.e., with the SCR conducting continuously, the full power available from the battery will not be delivered to the motor since some power will be consumed by the SCR and the circuitry for turning the SCR on and off. In addition, an SCR which can remain full-on and withstand the high currents present during such operations as ramp starts is very expensive.
The single FIGURE illustrates an SCR control for a direct current motor utilizing the bypass control of the present invention.
Referring now to the drawing, wherein is shown a preferred embodiment of the invention, main switch 11 enables a source of direct current, e.g., battery 12, to be connected to the circuit. Direction switches 16 and 17 are provided to alternatively energize one of the forward (F) or reverse (R) relay coils, to connect the field winding 18 in series with the armature 19. For example, if forward switch 16 is closed, it will complete an energizing path for the forward relay coil F through switch 16, normally closed contacts R.sub.3 and normally closed contacts BP.sub.3. When the forward relay coil F is energized it will close and open its main contacts F.sub.1 and F.sub.2, respectively, to connect the field winding in series with the armature. Current can also flow through the now closed contacts F.sub.4 and through resistor 13 and zener diodes 14 and 15 to develop regulated +12.4 and +6.2 voltages to power the control circuits described below.
Upon closure of main switch 11 and one of the direction switches 16 or 17, current can flow from the battery through the armature and field winding, primary 20 of pulse transformer 21 and the main silicon controlled rectifier (SCR) 22 and back to the battery.
Commutating capacitor 23 is connected in series with commutating SCR 24; the capacitor and SCR 24 being in parallel with the main SCR 22. A charging path for capacitor 23 is provided by the loop comprised of capacitor 23, the secondary 25 of pulse transformer 21 and the charging SCR 26.